Volume Two May 2014

Appendix 22

Ecosystem Modelling of the Chatham Rise (Pinkerton 2013)

Ecosystem Modelling of the Chatham Rise

Prepared for Chatham Rock Phosphate

April 2013

Authors/Contributors : Matt Pinkerton

For any information regarding this report please contact: Matt Pinkerton Principal Scientist Coasts & Oceans +64-4-386 0369 [email protected]

National Institute of Water & Atmospheric Research Ltd 301 Evans Bay Parade, Greta Point Wellington 6021 Private Bag 14901, Kilbirnie Wellington 6241 New Zealand

Phone +64-4-386 0300 Fax +64-4-386 0574

NIWA Client Report No: WLG2013-17 Report date: April 2013 NIWA Project: CRP12302

Catch of mesopelagic fish on Fisheries Oceanography I voyage to Chatham Rise, TAN0806. [Len Doel, Teacher Fellow, NIWA]

© All rights reserved. This publication may not be reproduced or copied in any form without the permission of the copyright owner(s). Such permission is only to be given in accordance with the terms of the client’s contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system.

Whilst NIWA has used all reasonable endeavours to ensure that the information contained in this document is accurate, NIWA does not give any express or implied warranty as to the completeness of the information contained herein, or that it will be suitable for any purpose(s) other than those specifically contemplated during the Project or agreed by NIWA and the Client.

Contents

Executive summary ...... 7

1 Introduction ...... 8

2 Modelling approach ...... 9 2.1 Study region ...... 9 2.2 Model structure ...... 10 2.3 Initial parameter estimation ...... 13 2.4 Balancing methodology ...... 16 2.5 Trophic levels ...... 16 2.6 Trophic Importance ...... 16

3 Results ...... 18

4 Discussion & Conclusions ...... 36

5 Acknowledgements ...... 38

6 References ...... 39

Appendix A Birds ...... 45

Appendix B Cetaceans ...... 54

Appendix C Seals ...... 91

Appendix D Fish ...... 102

Appendix E Mesopelagics ...... 123

Appendix F Phytoplankton ...... 143

Appendix G Microbial loop ...... 152

Appendix H Benthos and hyperbenthos ...... 160

References ...... 179

Ecosystem Modelling of the Chatham Rise

Tables Table 1: Summary of groups and parameter estimation used in the Chatham Rise trophic model. 14 Table 2: Initial estimates of model parameters (see Appendices for information on derivation). EE=Ecotrophic efficiency; B=Biomass; P/B=annual production to biomass ratio; Q/B=annual consumption to biomass ratio; P/Q=growth efficiency; Acc=accumulation as a fraction of annual production; Export, X as a fraction of annual production; U=Unassimilated consumption; T S=seasonal transfers (water column particulate detritus to benthos) as a fraction of annual inflow to the group. 20 Table 3a: Initial estimates of diet parameters for the Chatham Rise trophic model showing predator groups 1-18. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1. Entries of “0.00” imply that the diet fraction is >0% and <0.5%. 21 Table 3b: Initial estimates of diet parameters for the Chatham Rise trophic model showing groups 19-37. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1 for consumers. Entries of “0.00” imply that the diet fraction is >0% and <0.5%. 22 Table 4: Relative uncertainty (K) parameters for the Chatham Rise trophic model, with higher K values indicating higher relative uncertainty in the parameter. K E=uncertainty in ecotrophic efficiency parameters; KB=uncertainty in biomass parameters; K P=uncertainty in production parameters (P/B); K PQ = uncertainty in growth efficiency factor (P/Q); KA = uncertainty in accumulation parameters; K X= uncertainty in export parameters; K F = uncertainty in fishery catch parameter; K U=uncertainty in unassimilated consumption parameters; K S=uncertainty in seasonal transfer parameters; K D=uncertainty in diet parameters. 23 Table 5: Changes to Biomass (B), Production (P/B), growth efficiencies (P/Q) and diet fractions (D) during the SVD balancing process. Each line shows the parameter, the trophic group in the model, the original value of the parameter, an arrow (->), the final value of the parameter (in the balanced model), and the % change in square brackets. For diet fractions, the actual change in diet fraction (not the proportion) is shown. Within each type of parameter, the changes are ranked in descending magnitude. All changes of more than 10% are shown. 24 Table 6: Trophic group parameters for the balanced trophic model. Initial estimates of model parameters. EE=Ecotrophic efficiency; B=Biomass; P/B=annual production to biomass ratio; Q/B=annual consumption to biomass ratio; P/Q=growth efficiency; Acc=accumulation as a fraction of annual production; Export, X as a fraction of annual production; U=Unassimilated consumption; T S=seasonal transfers (water column particulate detritus to benthos) as a fraction of annual inflow to the group. 25

Ecosystem Modelling of the Chatham Rise

Table 7a: Diet parameters in the balanced model of the Chatham Rise showing groups 1-18. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1. Entries of “0.00” imply that the diet fraction is >0% and <0.5%. 26 Table 7b: Diet parameters in the balanced model of the Chatham Rise showing groups 19-37. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1 for consumers. Entries of “0.00” imply that the diet fraction is >0% and <0.5%. 27 Table 8: Output parameters for the Chatham Rise trophic model. The table shows trophic levels, respiration quotients (R/B), trophic importances (TI) by two methods and rank of trophic importance (1=highest). 31

Figures Figure 1: Depth of water over the Chatham Rise. High values are red; low values are blue (range 0–5100 m). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m. 10 Figure 2: Net primary production (NPP) in 14 large marine ecosystems (Conti & Scardi, 2010) compared with that for the Chatham Rise estimated in this study. Ecosystems compared are taken from the Atlantic Ocean (blue bars), Pacific Ocean (green bars) and Eastern Boundary Currents (pink bars). 28 Figure 3: Single-step trophic impact matrix, Q, for the Chatham Rise based on the balanced model. Positive impacts are shown white and negative are black, with the diameter of the circle proportional to the magnitude of the effect. The “impact” is interpreted as the effect that a small increase in the biomass of the impacting group (shown on the left of the diagram) may have on the biomass of the impacted group (shown across the top). 33 Figure 4: Multiple-step mixed trophic impact matrix, M, for the Chatham Rise. Positive impacts are shown white and negative are black, with the diameter of the circle proportional to the magnitude of the effect. 34 Figure 5: Trophic importance TI1 from the ecosystem model of the Chatham Rise shown in descending order of importance. The labels are in equivalent descending order of importance, numbers being their rank importance. TI1 is based on single-step impact matrix (Q), summing by absolute values. The coloured lines show the effect of increasing the biomass of corals (square symbols, red lines) and encrusting_inverts (triangle symbols, green lines) by a factor of 10, rebalancing the model and recalculating the index of trophic importance. This sensitivity analysis was carried out because there were limited data on the biomass of these sessile megafaunal groups available. 35 Figure 6: Trophic importance TI2 from the ecosystem model of the Chatham Rise shown in descending order of importance. The labels are in equivalent descending order of importance, numbers being their rank importance. TI2 is based on the multiple-step impact matrix (M), summing by absolute values. The coloured lines show the effect of increasing the

Ecosystem Modelling of the Chatham Rise 5

biomass of corals (square symbols, red lines) and encrusting_inverts (triangle symbols, green lines) by a factor of 10, rebalancing the model and recalculating the index of trophic importance. This sensitivity analysis was carried out because there were limited data on the biomass of these sessile megafaunal groups available. 36

Reviewed by Approved for release by

Dave Bowden Julie Hall

Ecosystem Modelling of the Chatham Rise

Executive summary A balanced model of the foodweb of the Chatham Rise was developed by bringing together information on all biota in the ecosystem. Key information derived and summarised in the report includes key species, their biomass, energetics (feeding and growth rates; assimilation efficiencies) and diets. The model has 37 groups: seabirds, toothed whales & dolphins, baleen whales, seals; 9 demersal fish groups (hoki, orange roughy, oreos, warehous, pelagic foragers, benthopelagic and benthic invertebrate feeders, benthopelagic and benthic predators, small demersal fishes); 4 mesopelagic groups (mesopelagic fishes, squid, krill, salps); 10 groups of benthic invertebrates (corals; other encrusting invertebrates; seastars & brittlestars; echinoderms; sea cucumbers; prawns & shrimps; large benthic worms; bivalves & gastropods; macrobenthos; meiobenthos); 3 groups of small zooplankton (mesozooplankton, ciliates, flagellates); phytoplankton, bacteria and detritus.

Substantial deficits in information remain in all groups and the initial set of parameters were adjusted to achieve mass balance taking into account the relative uncertainties in the parameters and allowing for the huge range of biomasses in the model (more than 4 orders of magnitude). Changes to the initial parameter set during balancing were plausible and generally low, though some changes up to 45% were needed. The balanced model is but one solution of many that may be considered consistent with the available data. Further research to explore the effects of parameter uncertainty on characteristics of the model would be useful.

Net primary production (NPP) of the Chatham Rise is moderate compared to other regions around the world that support large-scale fisheries. Most (83%) of NPP is remineralized within the lower pelagic food-web. The main pathways of energy to the middle foodweb include arthropods, small demersal fishes, mesopelagic fishes, squid, krill and salps. These 6 mesopelagic groups provide 82% of the food for demersal fishes and 99% of the food for air- breathing predators. In the model, the transfer of organic matter to the benthos by passive settling flux of particulate detrital material is 2.6% of NPP. The total energy supply to the benthos is only 20% of the production of mesozooplankton in the water column.

Trophic impact matrices were calculated from the balanced model showing the change in one group due to a small change in another group. “Trophic importance” is defined as effect of one group on all other groups and describes how important a group is to the structure and function of the ecosystem. Small demersal fishes and mesozooplankton were the most ecologically important consumer groups based on the multi-step analysis. Mesopelagic fishes, hoki, and arthropods also had high trophic importances in the multi-step analysis. Benthic meiofauna had high trophic importance (8th most important in the multi-step analysis). All the megabenthos groups had trophic importances in the lower half of groups in the model. Sensitivity analysis showed that 10 fold increases in the biomass of corals and encrusting invertebrates led to only small increases in their trophic importances.

The analysis presented here provides information at the spatial scale of the whole Chatham Rise and averaged over a typical year and provides information about trophic connections only; provision of habitat is not considered by the model.

Ecosystem Modelling of the Chatham Rise 7

1 Introduction Whole ecosystem modelling is being increasingly used as a tool for analysis of ecosystem structure and function (e.g. Bradford-Grieve et al. 2003; Pauly et al. 1998). There are a number of approaches to quantitative end-to-end modelling of marine ecosystems (reviewed by Plagányi, 2007). An important distinction is between dynamic models and static models. The former simulate changes in ecosystem properties over time based on the model structural assumptions and parameters. Their behaviour tends to be highly dependent on the assumptions of the underlying mechanistic connections in the system which are often poorly known. In contrast, the model presented is a static model based on the Ecopath approach (Christensen et al. 2000). Flows of a semi-conservative tracer through various trophic compartments of the ecosystem over a given period (1 year) are balanced. This kind of modelling is often called “mass-balance” and the focus is on trophic transfers of material i.e. the feeding of one organism on another. Static models such as the one developed here are descriptive of the state of the ecosystem at a particular point in time. Although they cannot be run to predict the future, they can be used to understand the characteristics of the system from which inferences as to system dynamics can be made. The development of this Chatham Rise ecosystem model should be viewed as serving a number of useful purposes

• It forces the critical assembly of a large amount of data on all components of the ecosystem in a form where they may be combined and intercompared. The model tests whether our current understanding of the ecosystem structure and function is complete and consistent. In assessing completeness, the model allows us to identify critical gaps in our knowledge, data, or approach.

• It acts as a basis for future ecosystem modelling, for example, the development of models that are seasonally resolved, spatially resolved, and capable of being run dynamically. The model may also allow us to identify sub-systems (for example, groups of interconnected species) that should subsequently be modelled in more detail.

• It formalises our conceptual model of ecosystem interconnectedness giving a quantitative model of energy flow through the system. This may be useful for suggesting system- level characteristics or properties of the system. For example, the model is used to identify key species or groups on which the system depends. Mixed Trophic Impact assessment is used for this analysis.

• A summary of the structure of the food-web of the Chatham Rise can be used to facilitate discussion by the varied stakeholders in the Chatham Rise ecosystem.

• In the future (but outside the scope of the present report), the model may help to identify candidate indicators of ecosystem state, which will be useful in monitoring for major changes in Chatham Rise ecosystem over time.

8 Ecosystem Modelling of the Chatham Rise

Although a trophic model such as that presented here is not, in itself, sufficient to assess the ecological effects of subsea mining on the ecosystem, a coherent and consistent picture of ecosystem function, once developed, can be used to explore potential relative sensitivities of the ecosystem to effects of mining.

This report follows on from two preliminary versions of the Chatham Rise ecosystem model (Pinkerton, 2008; Pinkerton, 2011a). The structure of this report is as follows: Section 2 describes the modelling methodology, including the choice of model domain. Section 3 describes the parameter estimation, and highlights changes from the previous version of the model (Pinkerton, 2011a). The detailed explanation on estimation of parameters for each group of the model is given in Appendices A to H. These 8 appendices cover all types of biota in the Chatham Rise ecosystem, reviewing the relevant parts of the literature on the various organisms, giving methods for parameters, and trophic linkages. Section 4 describes the results of the semi-objective model balancing, presents the balanced model, and the results of Mixed Trophic Impact analysis. Section 5 discusses the modelling, gives conclusions and recommendations for future work. 2 Modelling approach

2.1 Study region The study area for this work is the Chatham Rise, a broad submarine ridge about 800 km long and 300 km wide that extends eastwards from New Zealand landmass into the southwest Pacific Ocean (Figure 1). High phytoplankton abundance in this region is a conspicuous feature of ocean colour images of the Southern Ocean (e.g. Gordon et al. 1986; Banse & English 1997; Murphy et al. 2001). Elevated phytoplankton productivity is attributed to the presence of the Subtropical Front (STF) being bathymetrically locked to the Chatham Rise (Murphy et al. 2001; Sutton, 2001; Uddstrom & Oien, 1999). The STF above the Chatham Rise forms part of a 25,000 km-long convergence zone of northern Subtropical (ST) waters, and southern Subantarctic (SA) waters that encircles the globe. The mixing of nitrate-depleted ST water, with nitrate-rich SA water in the Chatham Rise region leads to elevated phytoplankton productivity (Boyd et al. 1999). Elevated oceanic productivity here is responsible for supporting the complex and valuable Chatham Rise ecosystem, including deep-water fisheries (e.g. orange roughy, oreo, hoki), an unusually rich benthic ecosystem, as well as seabird and marine mammal populations. The STF over the Chatham Rise is an area of vigorous mixing and eddy activity (e.g. Heath 1976; Belkin 1988; Uddstrom & Oien 1999; Stanton 1997; Chiswell 1994; Sutton 2001).

For the purposes of the modelling work, we define the study area as occupying the region bounded by the 250 m depth contour to the west (edge of the continental shelf) and the 1250 m depth contour elsewhere. The contours are linked at 172°E (SW corner) and 43°S (NW corner). This region has an area of approximately 222,800 km2. The mean depth of the region is 620 m. The Chatham Island group (close to 176.5°W) have an area of only 960 km 2 (<0.5% of the study region).

Ecosystem Modelling of the Chatham Rise 9

Figure 1: Depth of water over the Chatham Rise. High values are red; low values are blue (range 0– 5100 m). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m . 2.2 Model structure The trophic model developed here quantifies the transfer of organic material through a food web based on the widely used mass-balance identities of the Ecopath trophic model (Christensen & Walters 2004; Christensen & Pauly 2002). Biomass is presented in units of organic carbon density (gC m -2) and trophic flows in units of gC m -2 y-1. In quantifying the trophic structure of the ecosystem, the fundamental information includes the species present, abundances in terms of weight, the energetics of species (i.e. production, consumption, growth efficiency, respiration), and trophic interconnections between species through information on diets of predators. The model developed here also includes non-trophic transfers of organic carbon between groups. These transfers include: (1) unassimilated consumption (excreted material); (2) loss of material through exudants (e.g. primarily phytoplankton); (3) non-predation mortality (e.g. due to age, disease, starvation); (4) “messy eating” i.e. parts of animals that died due to predation but were not consumed at the time; (5) growth of biota which takes them from a smaller to a larger trophic group; (6) vertical sinking flux of detritus from the water column to the benthos; (8) long-term burial of organic material in the benthic sediments. Note that (2)+(3)+(4) are often described by an ecotrophic efficiency parameter.

We make the assumptions that there are no long term (e.g. decadal) trends. It is possible that there are considerable differences between years in many parts of the Chatham Rise ecosystem. This has two implications for developing a budgetary model. First, whereas long- term changes in ecosystem state may be small, there may be significant accumulations or loss of biogenic material over any given annual period. Second, measurements made in different years are not strictly comparable. In this study we attempt to reduce the effects of interannual variability on the budget by considering an annual period that is typical of a longer period, in this case chosen to be the period between October 2002 and December 2007.

10 Ecosystem Modelling of the Chatham Rise

Production is defined according to Equation 1. For non-detrital groups, production represents the intrinsic rate of growth of all individuals in the population. For detrital groups, production is the total net flow of organic matter into the group, including faecal material (unassimilated consumption) from consumers, dead organisms, non-consumed predation (“messy eating”), planktonic exudants, and transfers between groups. These latter transfers include, for example, the sinking of detrital/ungrazed material to the benthos. Carbon flow through each trophic group per year is balanced according to Equation 2 under the assumption that all parts of the ecosystem will be in balance in an average year. These balance equations provide a number of equality constraints to the system. Another set of equality constraints are provided by the fact that diet fractions of each predator sum to unity.

=  P  Pi Bi   Non-detrital groups [1a]  B i n   = 1−E +  Q  + s Pj ∑ P Tiji Uij   Tij  Detrital groups [1b] i=1   P i 

 n  n − 1−E + g + s − − −  Q  − = Pi 1 ∑(Tij Tij Tij ) X i Ai  ∑ Pj   Dij Fi 0 All groups [2]  j=1  j=1  P  j In these and other equations in this paper, for trophic group i:

-2 Bi annual average biomass (gC m ) -2 -1 Pi annual production (gC m y ). Autotrophic production rate is net of respiration but assumed to include production of phytoplankton exudants and other detrital material. -2 -1 Qi annual consumption (gC m y ). Note that autotrophs and detritus have Qi=0. -1 (P/B )i production/biomass ratio (y ) (Q/P )i reciprocal of the growth efficiency (dimensionless) Dij average fraction of prey i in the diet of predator j by weight (dimensionless) Xi fraction of production exported over year due to advection and migration (dimensionless) Ai fraction of production accumulated over a year (dimensionless) -2 -1 Fi fishing removals (gC m y ). 1-E Tij detrital transfer: fraction of production transferred from group i to detrital group j as non- living material, i.e. excluding direct predation but including phytoplankton exudants, parts of organisms (e.g. due to “messy eating”), whole dead organisms and carcasses (dimensionless) g Tij growth transfer: fraction of production transferred from group i to group j due to growth, i.e. as an organism gets older and/or larger it changes from one group to another (dimensionless) s Tij seasonal transfer: fraction of production transferred from group i to group j by non- trophic, seasonal processes, e.g. due to vertical flux of material (dimensionless) Uij fraction of food that has been consumed by component i but which is not assimilated, instead being passed to detrital group j, (dimensionless) n total number of groups in the model -2 -1 Ri loss of organic carbon from the system due to respiration (gC m y ). Respiration can be calculated as Ri=Qi·(1-Ui)-Pi

Ecosystem Modelling of the Chatham Rise 11

Note that Equations 1 and 2 differ from the standard Ecopath equations (Christensen & Walters 2004; Christensen & Pauly 2002) as follows. First, consumption is parameterised based on production and Q/P, the reciprocal of the growth efficiency, rather than being based on B and Q/B. This is done so that during model balancing, P/B and Q/B cannot vary independently and 1-E give unrealistic growth efficiencies. Second, the factor Tij is used instead of the Ecopath 1-E ecotrophic efficiency parameter, EE i, and is defined such that Tij =(1-EE i). This factor quantifies the fraction of production which is transferred from a living to detrital group(s) by processes other than unassimilated consumption. For example, it is known that a substantial part of primary organic material is not directly consumed but enters the detrital pool where it is decomposed by bacterial action. The proportion of net primary production undergoing these fates is given by the P·T1-E term for the phytoplankton group. Third, two new non-trophic transfer parameters are g s included: growth and seasonal transfers ( Tij , Tij ). Growth transfer allows organisms to move between model groups as they grow (e.g. small fish becoming medium sized fish). Seasonal transfers include physical movement of material between groups, for example, settling of water column detritus to form benthic detritus. Neither seasonal or growth transfer processes can easily be represented in standard Ecopath equations.

2.2.1 Trophic groups For the development of this kind of trophic model, all living organisms are grouped into a relatively small number of trophic groups. Too few groups will not allow the model to describe the trophic structure with sufficient subtlety, whereas too many groups can lead to spurious results because of lack of information to provide good parameterisation. Here, we use 37 trophic groups. The divisions we use include taxonomy (species or groups of species), function (e.g. water column primary producers), and sampling methodology (e.g. benthic organisms by size). Where possible, groups were chosen so that organisms combined into groups had similar characteristics such as size, energetics (growth, consumption, respiration rates), and similar trophic links (similar prey items, predators). The choice of groups was also constrained by the available information. It is assumed that the choice of groups does not affect the fundamental results of the modelling study though this has not yet been tested. The current groups are as follows.

• Apex predators (4 groups): seabirds; toothed whales & dolphins; baleen whales; seals (New Zealand seals and sea-lions).

• Demersal fish (10 groups on the basis of the Chatham Rise fish guilds identified in Dunn et al. submitted): hoki; orange roughy; oreos (spiky, black and smooth); warehous; “Large javelinfish guild” representing pelagic foragers; “Small javelinfish guild” representing benthopelagic invertebrate feeders; hake guild (representing benthopelagic predators); “rattails & ghost sharks guild” representing benthic invertebrate feeders; and “ling guild” representing benthic predators; small (cryptic) demersal fishes.

• Mesopelagics (4 groups): these are middle-trophic level groups living predominantly in the water column: Mesopelagic fishes (dominated by myctophids); cephalopods (mainly pelagic squids but also including benthic octopods); hard-bodied macrozooplankton (mainly krill); gelatinous zooplankton (like salps and jellyfishes).

12 Ecosystem Modelling of the Chatham Rise

• Benthic invertebrates (10 groups): corals (hard and soft corals); other encrusting invertebrates (including Ascidiacea, Bryozoa, Crinoidea, Hydrozoa, Porifera); sea-stars and brittlestars (Asteroidea, Ophiuroidea, Pycnogonida); echinoderms; holothurians (sea cucumbers); decapods, including crabs; large benthic worms (mainly polychaetes); shelled megabenthos (including bivalves, gastropods and giant forams); macrobenthos (both infauna and hyperbenthic epifauna); meiobenthos (mainly nematodes).

• Microzooplankton (3 groups): mesozooplankton (mainly copepods), heterotrophic microplankton (ciliates), heterotrophic flagellates.

• Phytoplankton.

• Bacteria (2 groups): water column bacteria; benthic bacteria (in soft sediments)

• Detritus (3 groups): particulate and dissolved water column detritus; benthic detritus; carcasses. 2.3 Initial parameter estimation There is a huge amount of information on the physical environment of the Chatham Rise and its flora and fauna, including physiology, life histories, energetics, and ecology. Detailed information on the estimation of the biomass, energetic parameters, and diets for each trophic group are given in Appendices A-H. Summary information is given in Table 2 and Table 3.

Ecosystem Modelling of the Chatham Rise 13

Table 1: Summary of groups and parameter estimation used in the Chatham Rise trophic model.

Group Description Information on parameter estimation for group Appendix All birds that breed in the study area or visit the Parameters estimated for 78 species of bird separately then A study area, that take some or all their food from combined according to estimated biomass. Taylor (2000a,b) used 1 Birds the sea. for biomass. Odontoceti: sperm whale, pilot whale, common Parameters estimated for 12 species/groups of toothed whales B dolphin, killer whale, dusky dolphin, bottlenose and dolphins then combined according to estimated biomass. dolphin, false killer whale, beaked whales, Kaschner (2004) “relative environmental suitability” mapping used 2 Toothed_whales southern bottlenose whale to help estimate biomass. Mysticeti: right whale, minke whale, blue whale, 3 Baleen_whales sei whale, humpback whale New Zealand fur seal; Hooker’s sealion Parameters estimated for 2 species then combined according to C 4 Seals estimated biomass. 5 Hoki Hoki Parameters estimated for 50 highest biomass species then D combined according to estimated biomass. Groups determined 6 Orange_roughy Orange roughy by species, species-group or feeding guild (Dunn et al., 7 Oreos Black oreo, spiky oreo, smooth oreo submitted).Biomass of assessed groups based on stock models. 8 Warehous Silver warehou, white warehou Other biomasses by scaling to trawl survey catch. Commercial catch of QMS species according to Ministry of Primary Industries 9 Large_javelinfish_guild Pelagic foragers: javelinfish (large), alfonsino annual fisheries plenary. Catch of non-QMS species consistent Benthopelagic invertebrate feeders: javelinfish with observer data (Livingston et al. 2003). Production by Banse (small), banded bellowsfish, Olivers rattail, & Mosher (1980). Consumption according to Palomares & Pauly 10 Small_javelinfish_guild orange perch (1998). Benthopelagic predators: hake, spiny dogfish, giant stargazer, barracouta, shovelnose spiny 11 Hake_guild dogfish Benthic invertebrate feeders: Bollons rattail, ghost shark, pale ghost shark, oblique banded 12 Rattails_&_ghost_sharks rattail, long-nosed chimaera Benthic predators: ling, lookdown dory, sea 13 Ling_guild perch, smooth skate, red cod Myctophids and other small midwater fishes, Acoustic estimates of biomass (McClatchie & Dunford 2003; E including juvenile fishes. O’Driscoll et al., 2009 ). Further data from TAN0806 and TAN1116 14 Mesopelagic_fish Fisheries Oceanography voyages not yet available. Pelagic squids and benthic octopods. Includes No reliable estimates of biomass, productivity or consumption 15 Cephalopods arrow squid. rates. Hard-bodied (mainly crustacean) Acoustic and midwater net data used to estimate biomass 16 Macrozoo_krill macrozooplankton (>20 mm length) (Gauthier et al., submitted). Soft-bodied macrozooplankton, including jellyfish (medusa), salps, siphonophores and 17 Macrozoo_gelatinous chaetognaths

14 Ecosystem Modelling of the Chatham Rise

All hard and soft corals, including Pennatulacea Benthic megafauna: organisms living on or near the seabed that H 18 Corals can be observed in near-bottom video or camera images Ascidians, crinoids, bryozoa, hydrozoan, porifera (approx.. >20 mm in size. 241 operational taxonomic units 19 Encrusting_inverts (sponges) categorized into 20 Stars_&_crabs Sea-stars, brittlestars, spider crabs 22 functional groups. Densities obtained from 108 Deep Towed Imaging System (DTIS) video transects over Chatham Rise All echinoderms 21 Echinoderms (Bowden, 2011). Densities extrapolated to whole area using 22 Holothurians Sea cucumbers biogenic habitats (Hewitt et al. 2011). Mean sizes measured on Decapod crustaceans (shrimps, prawns, squat Ocean Survey 20-20 voyage (Bowden, 2011). 23 Decapods lobsters); also large isopods 24 Large_benthic_worms Polychaetes, hemichordata 25 Shelled_megabenthos Bivalves, gastropods, giant forams, brachiopods Benthic epifauna and infauna between 0.5 and 20 Macrofaunal infaunal biomass on the Chatham Rise measured on mm a number of N-S transects close to longitude 180° (Nodder et al. 2003; Probert et al., 1996). Epifaunal biomass from Brenke sled 26 Macrobenthos catches on Ocean Survey 20-20 (Lorz, 2010; Bowden 2011) Benthic meiofauna (infauna 63 µm–0.5 mm); Multicorer measurements of meiofaunal biomass on the Chatham 27 Meiobenthos mainly nematodes Rise (Nodder et al, 2011; Nodder et al. 2003) Mesozooplankton (0.2–20 mm); dominated by Shipboard data from the Chatham Rise region (Bradford-Grieve G 28 Mesozooplankton copepods et al., 1998, 1999; Hall et al. 1999; Safi & Hall, 1999; J. Hall, 29 Ciliates Microzooplankton (20–200 µm); primarily ciliates. unpublished data). Heterotrophic nanoplankton (2.0–20 µm): 30 Het_flagellates primarily heterotrophic flagellates Phytoplankton and primary production The long-term annual average chlorophyll-a for the study region F from MODIS-Aqua data (2002–2012). Converted to biomass using mixed layer depth and carbon:chl ratios. Primary production from Vertically Generalized Production Model (Behrenfeld & 31 Phytoplankton Falkowski 1997a; Behrenfeld et al. 2002). Water column bacteria Shipboard data from the Chatham Rise region (Bradford-Grieve G 32 Bacteria_water et al., 1998, 1999; Smith and Hall, 1997; J. Hall, unpublished data Bacteria in soft sediments Measurements of benthic bacterial biomass and production at 10 H 33 Bacteria_sediment stations across the Chatham Rise (Nodder et al. 2003) Bodies of larger animals, including fisheries Discard rates of each fishery estimated. Natural non-predation 34 Carcasses discards mortality rates of larger animals poorly known. Particulate and dissolved organic detritus in the Only flows of organic detrital matter estimated. Mass of organic 35 Detritus_water water column carbon in detrital groups not relevant to model and not estimated. Particulate detritus on the seabed and interstitial Particulate organic carbon flux to benthos estimated for the dissolved organic matter region based on model of Lutz et al. (2007) fitted to floating 36 Detritus_benthic sediment trap data (Nodder & Gall, 1998).

Ecosystem Modelling of the Chatham Rise 15

2.4 Balancing methodology In this version of the Chatham Rise trophic model we used the semi-objective balancing method first described in Pinkerton et al. (2010) and subsequently refined (Pinkerton, 2011b). Each of the model parameters initially estimated has an associated uncertainty because the values are imperfectly and incompletely observed, and because the parameters vary between years and hence differ from our modeled average recent year. We hence adjust our preliminary estimates of all parameters to obtain a model where all the equality constraints are fulfilled. Models such as this are highly under-constrained, often with >3 times more parameters than constraints imposed by the modeling framework (Pinkerton et al. 2010), so there is a large family of possible solutions all of which are feasible according to the conceptual model. We want to find the solution that is “closest” to our initial set of estimated parameters as defined below. The problem at this stage is non-linear and we adopt an iterative approach to search for this solution by simultaneously adjusting all parameters. The system is first linearised and then Singular Value Decomposition (SVD: Press et al. 1992) is applied to find the adjustment vector which minimises the “cost function”. The “cost function” provides a measure of the overall amount of change to parameters needed to achieve balance, taking into account relative uncertainties between parameters and ensuring even adjustment across groups in the model. Minimizing the cost function hence finds the balance point which is “closest” to our initial parameter set in highly multi-dimensional parameter space. More information on the cost function is given in Pinkerton et al. (2010). In order to use an objective balancing method such as this, it is necessary to assign relative magnitudes to the uncertainties of all parameters in the model. Whereas it is possible to assign uncertainties to some parameters by using information on the variability associated with various parts of the data used in their derivations, an entirely objective approach is not possible for all parameters for all groups. As a solution to the problem of assigning uncertainties to parameters consistently, Kavanagh et al. (2004) suggested that a “data pedigree” approach was useful. In the approach given by Kavanagh et al. (2004), parameters were assigned indices representing their relative uncertainties, and these pedigree indices were mapped onto numerical uncertainty factors. We used a similar method here to give values shown in Table 4. Although still more arbitrary than ideal, this method of assigning relative uncertainties to parameters and then adjusting all parameters simultaneously to minimize a cost function is an improvement on other methods currently available (e.g. Kavanagh et al., 2004) and leads to a plausible balanced model. The sensitivity of the balanced model to different uncertainty factors is discussed later. 2.5 Trophic levels We calculated trophic levels (Lindeman 1942, Christensen & Pauly 1992) in the balanced model using matrix inversion based on two rules. First, primary producers, detritus and bacteria were defined as having a trophic level of 1. Second, a consumer’s trophic level was defined as the sum of the trophic levels of their prey items, weighted by diet fraction, plus one. 2.6 Trophic Importance Based on a balanced food-web model, methods exist for calculating the average “trophic importance” (sensu Libralato et al. 2006) of the species or model groups. Trophic importance

16 Ecosystem Modelling of the Chatham Rise

(TI) is a measure of the overall effect on food-web structure of changes to the abundance of one group in the model. “Trophic importance” is preferred over “ecological importance” as only trophic effects are considered by the analysis. This measure is preferred over “keystoneness” since the meaning of the latter has become confused. Keystoneness was defined by Power et al. (1996) as the amount by which the trophic importance of a species exceeds that expected on the basis of abundance alone. Other interpretations of keystoneness essentially equate it to trophic importance (Libralato et al. 2006). In any case, trophic importance is the relevant measure in terms of assessing by how much changes in the abundances of species caught by the fishery are likely to affect the food-web, irrespective of whether those species have high or low biomass in the ecosystem.

If a balanced food-web model of the ecosystem of interest is available, the trophic importance of a given species can be calculated via the Mixed Trophic Impact (MTI) matrix, M. This matrix has elements mij and is often interpreted as the change in biomass of one group (the “impacted” group, j) due to a small change in the biomass in another group (the “impacting” group, i) (e.g. Libralato et al. 2006). First, a measure of the direct (one-step) trophic impact of species i on species j is written as element qij in the matrix Q, and defined as the difference between bottom- up (gij ) and top-down effects (fij ) (equation 3, Ulanowicz & Puccia 1990).

= − qij g ij f ij [3]

Here, gij is the proportion of prey item i in the diet of predator j, and fij is the fraction of the net production of prey item j that is consumed by predator i (Ulanowicz & Puccia 1990). “Net production” excludes respiratory output and is equal to “production” ( P) in Ecopath and Ecosim models (Christensen & Walters, 2004; Christensen et al. 2008). The MTI matrix M is calculated as equation 4 to take into account indirect food-web effects, that is, impacts of one species on another via multiple steps through the food-web (Ulanowicz & Puccia 1990). Here, I is the identity matrix of size n by n where n is the number of groups in the model.

Mt = (I − Qt )−1 − I [4]

Ecosystem Modelling of the Chatham Rise 17

Libralato et al. (2006) suggest calculating TIi (the trophic importance of species i) as the root mean square value of mij calculated over all j. In a similar approach, we use the sum of the absolute values which gives weak links higher and, we argue, more appropriate importance (McCann et al. 1998; McCann 2000; Pinnegar et al. 2005). The use of the absolute function rather than the squared function also means that the result will be less sensitive to the number and types of trophic groups in the model. Trophic importance with reference to small perturbations of the ecosystem can be estimated from the single-step trophic impact matrix, Q (Equation 5) or the multiple-step matrix, M (Equation 6). The former (hereafter called TI1) focuses on direct (first order) predator-prey linkages and does not consider how these effects may propagate through the food-web. In contrast, the latter, based on M (hereafter called TI2) considers multiple interactions in the ecosystem and hence may capture more diffuse or higher- order effects. It is not known which of these approaches is more realistic or appropriate, so we calculate and compare both approaches.

n = TI1i∑ q ij [5] j=1 n = TI2i∑ m ij [6] j=1

3 Results

3.1.1 Model balancing The initial parameterisation of the model had 304 unknown variables and 67 constraints, implying a highly under-constrained system as expected. The balancing procedure applied over 8 iterations gave a steady solution within 1% of true balance for all groups. The main changes to biomass, P/B, and diets are summarized in Table 5. The balanced model values are given in Table 6 and Table 7.

Biomass parameters changed by between +44% (krill) and -45% (cephalopods), with a mean absolute change of 6.7% and median absolute change of 1.3%. Production parameters (P/B) changed by between +7% (krill) and -11% (rattails & ghost sharks), with a mean absolute change of 2.2% and median absolute change of 0.9%. Changes to most growth efficiency parameters (P/Q) were small; only one change to P/Q were by more than 10% (rattails & ghost sharks). About 12% of the non-zero diet fractions (22 out of 185) changed by more than 10% during model balancing, with changes of between +33% and -37%. The mean absolute change in diet fractions during balancing was 4.0%.

18 Ecosystem Modelling of the Chatham Rise

The relative sizes of the changes between types of parameter and between trophic groups are determined by a combination of the uncertainty factors and the changes required to balance the model. These changes give an indication of inconsistencies within the initial set of parameters. The largest changes were for cephalopods, mesopelagic fish, small demersal fishes, gelatinous zooplankton and arthropods. Given the problems with estimating the biomass, energetics and diets of these groups (see Appendices for details), it is not unreasonable to suppose that we had estimated the parameters for these groups with larger uncertainties that for other groups. In general, the parameter changes required during model balancing are plausible.

Decreases in the estimated biomass and P/B, and increases in P/Q for several groups of demersal fishes (including hoki, orange roughy and oreos) show that the model was trying to reduce the consumption by these groups because there was not enough prey to satisfy their needs. This may be because the consumption of prey by these groups was overestimated in the initial parameter set, or may point to still more prey being available.

Considering changes in diets, the balancing procedure reduces the consumption of seastars and brittlestars by the fish feeding guild characterized by rattails and ghost sharks to near zero. It is possible that the biomass of seastars and brittlestars in the model is underestimated. The balancing procedure transfers almost all consumption by mesopelagic fishes to mesozooplankton and away from macrozooplankton (hard and soft bodied) and cephalopods, because the latter three prey groups are in excess demand by other predators which were set to have less uncertain diets (especially groups of demersal fishes). Further information on the abundance of middle-trophic level prey species (especially decapods, small demersal fishes, mesopelagic fishes, hard- and soft-bodied macrozooplankton, and benthic macrofauna) at the scale of the Chatham Rise would be needed to better constrain the model.

Ecosystem Modelling of the Chatham Rise 19

Table 2: Initial estimates of model parameters (see Appendices for information on derivation). EE=Ecotrophic efficiency; B=Biomass; P/B=annual production to biomass ratio; Q/B=annual consumption to biomass ratio; P/Q=growth efficiency; Acc=accumulation as a fraction of annual production; Export, X as a fraction of annual production; U=Unassimilated consumption; T S=seasonal transfers (water column particulate detritus to benthos) as a fraction of annual inflow to the group.

Group B P/B Q/B EE P/Q Acc Export Fishery U Seasonal Detritus Carcass Seas. -2 -1 -1 -2 -1 gC m y y A/P X/P gC m y TS/P Fate Fate Fate 1 Birds 1.1E-03 0.29 104.1 0.00 0.003 0 0 0 0.30 0 36 35 0 2 Toothed_whales 6.5E -04 0.05 8.2 0.90 0.006 0 0 0 0.20 0 36 35 0 3 Baleen_whales 5.0E -04 0.04 0.6 0.00 0.079 0 0 0 0.20 0 36 35 0 4 Seals 1.9E-04 0.18 18.6 0.00 0.010 0 0 0 0.20 0 36 35 0 5 Hoki 8.7E-02 0.42 2.7 0.95 0.159 0 0 1.30E-02 0.27 0 36 35 0 6 Orange_roughy 3.5E-02 0.25 2.9 0.94 0.086 0 0 4.03E-03 0.27 0 36 35 0 7 Oreos 6.8E-02 0.37 2.1 0.97 0.174 0 0 3.82E-03 0.27 0 36 35 0 8 Warehous 1.7E-02 0.42 3.6 0.93 0.119 0 0 3.30E-03 0.27 0 36 35 0 9 Large_javelinfish_guild 1.2E -02 0.39 2.7 0.85 0.145 0 0 3.59E -04 0.27 0 36 35 0 10 Small_javelinfish_guild 8.7E-03 0.43 2.9 0.89 0.150 0 0 3.18E-04 0.27 0 36 35 0 11 Hake_guild 3.5E-02 0.35 2.3 0.80 0.153 0 0 3.89E-03 0.27 0 36 35 0 12 Rattails_&_ghost_sharks 2.7E-02 0.47 3.0 0.85 0.156 0 0 1.12E-03 0.27 0 36 35 0 13 Ling_guild 4.3E-02 0.33 2.2 0.97 0.154 0 0 2.99E-03 0.27 0 36 35 0 14 Small_demersal_fish 2.2E-01 0.90 4.4 0.95 0.204 0 0 0 0.27 0 36 35 0 15 Mesopelagic_fish 3.0E -01 1.43 7.1 0.99 0.200 0 0 0 0.13 0 36 35 0 16 Cephalopods 3.3E-02 8.60 34.4 0.99 0.250 0 0 4.79E-03 0.13 0 36 35 0 17 Macrozoo_krill 2.2E-02 8.00 26.7 0.95 0.300 0 0 0 0.13 0 36 35 0 18 Macrozoo_gelatinous 2.7E-02 10.00 25.0 0.95 0.400 0 0 0 0.50 0 36 35 0 19 Corals 1.7E-03 0.82 3.3 0.75 0.250 0 0.52 0 0.30 0 37 35 0 20 Encrusting_inverts 1.8E-03 0.46 1.8 0.95 0.250 0 0.26 0 0.30 0 37 35 0 21 Seastars_&_brittlestars 4.3E-03 0.70 2.8 0.95 0.250 0 0 0 0.30 0 37 35 0 22 Echinoids 8.1E-04 0.35 2.4 0.95 0.150 0 0.22 0 0.30 0 37 35 0 23 Holothurians 1.3E-04 0.35 2.0 0.00 0.176 0 0 0 0.30 0 37 35 0 24 Arthropods 2.0E-01 1.40 5.8 0.95 0.240 0 0 0 0.30 0 37 35 0 25 Large_benthic_worms 5.4E-04 2.78 11.6 0.95 0.240 0 0 0 0.30 0 37 35 0 26 Shelled_megabenthos 3.5E-04 1.33 7.2 0.95 0.185 0 0.42 0 0.30 0 37 35 0 27 Macrobenthos 2.9E-01 0.82 2.3 0.95 0.350 0 0 0 0.30 0 37 37 0 28 Meiobenthos 1.2E-01 10.00 32.3 0.15 0.310 0 0 0 0.30 0 37 37 0 29 Mesozooplankton 1.3E+00 30.00 85.7 0.90 0.350 0 0 0 0.30 0 36 36 0 30 Ciliates 8.6E-02 90.00 255.7 0.90 0.352 0 0 0 0.20 0 36 36 0 31 Het_flagellates 2.8E-01 200.00 555.6 0.90 0.360 0 0 0 0.20 0 36 36 0 32 Phytoplankton 2.9E+00 96.48 NA 0.45 NA 0 0 0 NA 0 36 36 0 33 Bacteria_water 1.1E+00 60.00 185.8 1.00 0.323 0 0 0 0.00 0 36 36 0 34 Bacteria_sediment 1.3E+00 1.00 3.3 1.00 0.300 0 0 0 0.00 0 37 37 0 35 Carcasses NA NA NA NA NA 0 0 0 NA 0 NA NA 0 36 Detritus_water NA NA NA NA NA 0 0 0 NA 0.033 NA NA 37 37 Detritus_benthic NA NA NA NA NA 0.10 0 0 NA 0 NA NA 0

20 Ecosystem Modelling of the Chatham Rise

Table 3a: Initial estimates of diet parameters for the Chatham Rise trophic model showing predator groups 1-18. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1. Entries of “0.00” imply that the diet fraction is >0% and <0.5%. Predators Prey 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 Birds 2 Toothed_whales 0.01 3 Baleen_whales 4 Seals 5 Hoki 0.02 0.23 0.05 0.17 0.11 0.01 6 Orange_roughy 0.00 0.07 7 Oreos 0.02 0.09 0.18 8 Warehous 0.00 0.04 0.09 9 Large_javelinfish_guild 0.00 0.04 0.07 10 Small_javelinfish_guild 0.00 0.07 0.01 0.04 11 Hake_guild 0.01 0.09 0.01 12 Rattails_&_ghost_sharks 0.01 0.14 0.02 0.02 0.01 13 Ling_guild 0.01 0.01 0.02 0.05 14 Small_demersal_fish 0.05 0.25 0.31 0.22 0.18 0.01 0.16 0.12 0.03 15 Mesopelagic_fish 0.46 0.25 0.16 0.20 0.22 0.21 0.02 0.33 0.03 0.02 0.02 0.20 16 Cephalopods 0.10 0.60 0.01 0.50 0.05 0.19 0.02 0.19 0.03 0.02 0.02 0.05 17 Macrozoo_krill 0.38 0.01 0.67 0.02 0.04 0.09 0.21 0.04 0.06 0.05 0.20 0.46 0.05 0.10 18 Macrozoo_gelatinous 0.06 0.01 0.06 0.01 0.44 1.00 0.04 0.06 0.09 0.10 19 Corals 20 Encrusting_inverts 21 Seastars_&_brittlestars 0.41 0.08 22 Echinoids 0.04 23 Holothurians 24 Arthropods 0.10 0.17 0.20 0.37 0.22 0.18 0.32 0.25 0.05 0.02 25 Large_benthic_worms 0.01 0.02 0.01 26 Shelled_megabenthos 0.02 0.08 27 Macrobenthos 0.01 0.01 0.02 0.03 0.24 0.17 0.27 0.05 28 Meiobenthos 0.20 29 Mesozooplankton 0.10 0.29 0.10 0.60 0.14 0.60 0.30 30 Ciliates 0.05 0.20 31 Het_flagellates 0.10 32 Phytoplankton 0.20 0.10 33 Bacteria_water 0.10 34 Bacteria_sediment 35 Carcasses 0.08 0.09 0.10 36 Detritus_water 0.10 37 Detritus_benthic

Ecosystem Modelling of the Chatham Rise 21

Table 3b: Initial estimates of diet parameters for the Chatham Rise trophic model showing groups 19-37. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1 for consumers. Entries of “0.00” imply that the diet fraction is >0% and <0.5%.

Predators Prey 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 1 Birds NA NA NA NA 2 Toothed_whales NA NA NA NA 3 Baleen_whales NA NA NA NA 4 Seals NA NA NA NA 5 Hoki NA NA NA NA 6 Orange_roughy NA NA NA NA 7 Oreos NA NA NA NA 8 Warehous NA NA NA NA 9 Large_javelinfish_guild NA NA NA NA 10 Small_javelinfish_guild NA NA NA NA 11 Hake_guild NA NA NA NA 12 Rattails_&_ghost_sharks NA NA NA NA 13 Ling_guild NA NA NA NA 14 Small_demersal_fish NA NA NA NA 15 Mesopelagic_fish NA NA NA NA 16 Cephalopods NA NA NA NA 17 Macrozoo_krill NA NA NA NA 18 Macrozoo_gelatinous NA NA NA NA 19 Corals 0.30 0.02 NA NA NA NA 20 Encrusting_inverts 0.10 0.30 0.05 NA NA NA NA 21 Seastars_&_brittlestars NA NA NA NA 22 Echinoids 0.10 0.05 NA NA NA NA 23 Holothurians NA NA NA NA 24 Arthropods NA NA NA NA 25 Large_benthic_worms 0.05 0.03 NA NA NA NA 26 Shelled_megabenthos 0.20 0.05 NA NA NA NA 27 Macrobenthos 0.25 0.05 0.20 0.50 0.15 0.10 NA NA NA NA 28 Meiobenthos 0.80 0.10 0.20 0.25 0.20 NA NA NA NA 29 Mesozooplankton 0.10 0.33 NA NA NA NA 30 Ciliates 0.05 0.06 NA NA NA NA 31 Het_flagellates 0.05 0.33 0.60 NA NA NA NA 32 Phytoplankton 0.28 0.40 0.55 NA NA NA NA 33 Bacteria_water 0.35 0.50 0.05 0.45 NA NA NA NA 34 Bacteria_sediment 0.20 0.20 0.10 0.30 0.15 0.10 0.35 0.17 NA NA NA NA 35 Carcasses 0.10 NA NA NA NA 36 Detritus_water 0.40 0.50 0.05 NA 1.00 NA NA NA 37 Detritus_benthic 0.20 0.20 0.10 0.30 0.15 0.10 0.35 0.83 NA 1.00 NA NA NA

22 Ecosystem Modelling of the Chatham Rise

Table 4: Relative uncertainty (K) parameters for the Chatham Rise trophic model, with higher K values indicating higher relative uncertainty in the parameter. K E=uncertainty in ecotrophic efficiency parameters; K B=uncertainty in biomass parameters; K P=uncertainty in production parameters (P/B); K PQ = uncertainty in growth efficiency factor (P/Q); KA = uncertainty in accumulation parameters; K X= uncertainty in export parameters; K F = uncertainty in fishery catch parameter; K U=uncertainty in unassimilated consumption parameters; K S=uncertainty in seasonal transfer parameters; K D=uncertainty in diet parameters.

Group KE KB KP KPQ KA KX KF KU KS KD 1 Birds 0.3 0.5 0.05 0 0 0 0 0 0 0.5 2 Toothed_whales 0.3 1 0.05 0 0 0 0 0 0 0.5 3 Baleen_whales 0.3 1 0.05 0 0 0 0 0 0 0.5 4 Seals 0.3 1 0.05 0 0 0 0 0 0 0.5 5 Hoki 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 6 Orange_roughy 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 7 Oreos 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 8 Warehous 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 9 Large_javelinfish_guild 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 10 Small_javelinfish_guild 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 11 Hake_guild 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 12 Rattails_&_ghost_sharks 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 13 Ling_guild 0.3 0.1 0.2 0.02 0 0 0 0 0 0.3 14 Small_demersal_fish 0.3 1 0.2 0.08 0 0 0 0 0 0.5 15 Mesopelagic_fish 0.3 1 0.2 0.08 0 0 0 0 0 0.5 16 Cephalopods 0.3 1 0.2 0.16 0 0 0 0 0 1 17 Macrozoo_krill 0.3 2 0.3 0.08 0 0 0 0 0 0.5 18 Macrozoo_gelatinous 0.3 2 0.3 0.08 0 0 0 0 0 0.5 19 Corals 0.3 0.5 0.3 0.16 0 0.20 0 0.1 0 0.5 20 Encrusting_inverts 0.3 0.5 0.3 0.16 0 0.20 0 0.1 0 0.5 21 Seastars_&_brittlestars 0.3 0.5 0.3 0.16 0 0 0 0.1 0 1 22 Echinoids 0.3 0.5 0.3 0.16 0 0.20 0 0.1 0 1 23 Holothurians 0.3 0.5 0.3 0.16 0 0 0 0.1 0 1 24 Arthropods 0.3 1 0.3 0.16 0 0 0 0.1 0 0.5 25 Large_benthic_worms 0.3 0.5 0.3 0.16 0 0 0 0.1 0 1 26 Shelled_megabenthos 0.3 0.5 0.3 0.16 0 0.20 0 0.1 0 1 27 Macrobenthos 0.3 1 0.3 0.16 0 0 0 0.1 0 0.5 28 Meiobenthos 0.3 0.5 0.3 0.16 0 0 0 0.1 0 1 29 Mesozooplankton 0.3 0.3 0.3 0.08 0 0 0 0.1 0 0.5 30 Ciliates 0.3 0.3 0.3 0.08 0 0 0 0.1 0 0.5 31 Het_flagellates 0.3 0.3 0.3 0.08 0 0 0 0.1 0 0.5 32 Phytoplankton 0.3 0.2 0.1 0 0 0 0 0 0 0 33 Bacteria_water 0.3 2 2 0.64 0 0 0 0 0 0 34 Bacteria_sediment 0.3 1 1 0.64 0 0 0 0 0 0 35 Carcasses 0 0 0 0 0 0 0 0 0 0 36 Detritus_water 0 0 0 0 0 0 0 0 2 0 37 Detritus_benthic 0 0 0 0 0.3 0 0 0 0 0

Ecosystem Modelling of the Chatham Rise 23

Table 5: Changes to Biomass (B), Production (P/B), growth efficiencies (P/Q) and diet fractions (D) during the SVD balancing process. Each line shows the parameter, the trophic group in the model, the original value of the parameter, an arrow ( ->), the final value of the parameter (in the balanced model), and the % change in square brackets. For diet fractions, the actual change in diet fraction (not the proportion) is shown. Within each type of parameter, the changes are ranked in descending magnitude. All changes of more than 10% are shown.

1 B Cephalopods 0.033445720 -> 0.018252446 [ -0.45426662 ] 2 B Macrozoo_krill 0.021998711 -> 0.031688022 [ 0.44044902 ] 3 B Macrozoo_gelatinous 0.026584871 -> 0.035595979 [ 0.33895624 ] 4 B Mesopelagic_fish 0.29847395 -> 0.21509829 [ -0.27933983 ] 5 B Small_demersal_fish 0.21819456 -> 0.17334559 [ -0.20554579 ] 6 B Arthropods 0.20000000 -> 0.22067802 [ 0.10339007 ] 7 B Macrobenthos 0.29290736 -> 0.31950602 [ 0.090809118 ]

1 P/B Rattails_&_ghost_sharks 0.47003981 -> 0.41793296 [ -0.11085625 ]

1 P/Q Cephalopods 0.25000000 -> 0.27819565 [ 0.11278262 ]

1 D Rattails_&_ghost_sharks<-Seastars_&_brittlestars 0.41071430 -> 0.041662869 [ -0.36905143 ] 2 D Mesopelagic_fish<-Mesozooplankton 0.60000002 -> 0.93475915 [ 0.33475912 ] 3 D Cephalopods<-Mesozooplankton 0.13525833 -> 0.41048767 [ 0.27522934 ] 4 D Cephalopods<-Macrozoo_krill 0.45558050 -> 0.18441943 [ -0.27116108 ] 5 D Seastars_&_brittlestars<-Shelled_megabenthos 0.20000000 -> 0.0010000000 [ -0.19900000 ] 6 D Mesopelagic_fish<-Macrozoo_krill 0.20000000 -> 0.0038123103 [ -0.19618769 ] 7 D Rattails_&_ghost_sharks<-Arthropods 0.18073593 -> 0.37645964 [ 0.19572371 ] 8 D Arthropods<-Macrobenthos 0.20000000 -> 0.0044764171 [ -0.19552359 ] 9 D Rattails_&_ghost_sharks<-Macrobenthos 0.17240259 -> 0.36060111 [ 0.18819852 ] 10 D Seastars_&_brittlestars<-Detritus_benthic 0.20000000 -> 0.36300755 [ 0.16300755 ] 11 D Seastars_&_brittlestars<-Bacteria_sediment 0.20000000 -> 0.36286495 [ 0.16286495 ] 12 D Hoki<-Mesopelagic_fish 0.22000000 -> 0.34493436 [ 0.12493436 ] 13 D Arthropods<-Detritus_benthic 0.30000001 -> 0.41380808 [ 0.11380806 ] 14 D Hoki<-Rattails_&_ghost_sharks 0.14000000 -> 0.027727558 [ -0.11227244 ] 15 D Arthropods<-Bacteria_sediment 0.30000001 -> 0.40794007 [ 0.10794005 ] 16 D Echinoids<-Corals 0.30000001 -> 0.19393311 [ -0.10606690 ]

24 Ecosystem Modelling of the Chatham Rise

Table 6: Trophic group parameters for the balanced trophic model. Initial estimates of model parameters. EE=Ecotrophic efficiency; B=Biomass; P/B=annual production to biomass ratio; Q/B=annual consumption to biomass ratio; P/Q=growth efficiency; Acc=accumulation as a fraction of annual production; Export, X as a fraction of annual production; U=Unassimilated consumption; TS=seasonal transfers (water column particulate detritus to benthos) as a fraction of annual inflow to the group.

Group B P/B Q/B EE P/Q Acc Export Fishery U Seasonal Detritus Carcass Seas. -2 -1 -1 -2 -1 gC m y y A/P X/P gC m y TS/P Fate Fate Fate 1 Birds 1.04E-03 0.29 103.86 0.00 0.00 0 0 0 0.30 0 36 35 0 2 Toothed_whales 6.45E-04 0.05 8.19 0.90 0.01 0 0 0 0.20 0 36 35 0 3 Baleen_whales 5.04E-04 0.04 0.55 0.00 0.08 0 0 0 0.20 0 36 35 0 4 Seals 1.83E-04 0.18 18.63 0.00 0.01 0 0 0 0.20 0 36 35 0 5 Hoki 8.50E-02 0.40 2.50 0.97 0.16 0 0 1.30E-02 0.27 0 36 35 0 6 Orange_roughy 3.51E-02 0.25 2.90 0.94 0.09 0 0 4.03E-03 0.27 0 36 35 0 7 Oreos 6.78E-02 0.37 2.10 0.98 0.17 0 0 3.82E-03 0.27 0 36 35 0 8 Warehous 1.76E -02 0.43 3.59 0.94 0.12 0 0 3.30E -03 0.27 0 36 35 0 9 Large_javelinfish_guild 1.18E-02 0.39 2.68 0.86 0.14 0 0 3.59E-04 0.27 0 36 35 0 10 Small_javelinfish_guild 8.75E-03 0.43 2.88 0.89 0.15 0 0 3.18E-04 0.27 0 36 35 0 11 Hake_guild 3.46E-02 0.34 2.24 0.82 0.15 0 0 3.89E-03 0.27 0 36 35 0 12 Rattails_&_ghost_sharks 2.58E-02 0.42 2.65 0.86 0.16 0 0 1.12E-03 0.27 0 36 35 0 13 Ling_guild 4.24E-02 0.32 2.05 0.97 0.15 0 0 2.99E-03 0.27 0 36 35 0 14 Small_demersal_fish 1.73E -01 0.88 4.12 0.96 0.21 0 0 0 0.27 0 36 35 0 15 Mesopelagic_fish 2.15E-01 1.35 6.55 0.99 0.21 0 0 0 0.13 0 36 35 0 16 Cephalopods 1.83E-02 7.79 28.01 0.99 0.28 0 0 4.79E-03 0.13 0 36 35 0 17 Macrozoo_krill 3.17E-02 8.53 28.37 0.95 0.30 0 0 0 0.13 0 36 35 0 18 Macrozoo_gelatinous 3.56E-02 10.51 26.23 0.94 0.40 0 0 0 0.50 0 36 35 0 19 Corals 1.69E -03 0.82 3.30 0.76 0.25 0 0.51 0 0.30 0 37 35 0 20 Encrusting_inverts 1.77E -03 0.46 1.84 0.95 0.25 0 0.26 0 0.30 0 37 35 0 21 Seastars_&_brittlestars 4.35E-03 0.71 2.73 0.96 0.26 0 0 0 0.30 0 37 35 0 22 Echinoids 7.93E-04 0.35 2.27 0.95 0.15 0 0.22 0 0.30 0 37 35 0 23 Holothurians 1.31E-04 0.35 1.98 0.00 0.18 0 0 0 0.30 0 37 35 0 24 Arthropods 2.21E-01 1.44 5.73 0.95 0.25 0 0 0 0.30 0 37 35 0 25 Large_benthic_worms 5.56E-04 2.82 11.73 0.95 0.24 0 0 0 0.30 0 37 35 0 26 Shelled_megabenthos 3.47E -04 1.32 7.12 0.95 0.19 0 0.42 0 0.30 0 37 35 0 27 Macrobenthos 3.20E-01 0.84 2.34 0.96 0.36 0 0 0 0.30 0 37 37 0 28 Meiobenthos 1.28E-01 10.32 33.25 0.22 0.31 0 0 0 0.30 0 37 37 0 29 Mesozooplankton 1.28E+00 29.82 84.92 0.90 0.35 0 0 0 0.30 0 36 36 0 30 Ciliates 8.58E-02 89.93 255.39 0.90 0.35 0 0 0 0.20 0 36 36 0 31 Het_flagellates 2.77E-01 200.49 556.63 0.90 0.36 0 0 0 0.20 0 36 36 0 32 Phytoplankton 2.86E+00 96.53 NA 0.46 NA 0 0 0 NA 0 36 36 0 33 Bacteria_water 1.16E+00 60.63 190.23 1.00 0.32 0 0 0 0.00 0 36 36 0 34 Bacteria_sediment 1.35E+00 1.04 3.46 1.00 0.30 0 0 0 0.00 0 37 37 0 35 Carcasses NA NA NA 1.00 NA 0 0 0 NA 0 NA NA 0 36 Detritus_water NA NA NA 1.00 NA 0 0 0 NA 0.033 NA NA 37 37 Detritus_benthic NA NA NA 1.00 NA 0.10 0 0 NA 0 NA NA 0

Ecosystem Modelling of the Chatham Rise 25

Table 7a: Diet parameters in the balanced model of the Chatham Rise showing groups 1-18. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1. Entries of “0.00” imply that the diet fraction is >0% and <0.5%. Predators Prey 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 Birds 2 Toothed_whales 0.01 3 Baleen_whales 4 Seals 5 Hoki 0.02 0.22 0.01 0.13 0.08 6 Orange_roughy 0.00 0.04 7 Oreos 0.02 0.08 0.16 8 Warehous 0.00 0.03 0.05 9 Large_javelinfish_guild 0.00 0.03 0.02 10 Small_javelinfish_guild 0.00 0.00 0.03 11 Hake_guild 0.00 0.07 0.01 12 Rattails_&_ghost_sharks 0.01 0.03 0.00 0.01 0.01 13 Ling_guild 0.01 0.01 0.03 0.07 14 Small_demersal_fish 0.05 0.28 0.29 0.18 0.17 0.01 0.17 0.13 0.00 15 Mesopelagic_fish 0.46 0.25 0.16 0.20 0.34 0.23 0.02 0.33 0.03 0.02 0.01 0.22 16 Cephalopods 0.10 0.61 0.01 0.51 0.08 0.22 0.03 0.25 0.04 0.03 0.00 0.05 17 Macrozoo_krill 0.37 0.01 0.67 0.04 0.05 0.09 0.21 0.05 0.12 0.05 0.00 0.18 0.02 0.03 18 Macrozoo_gelatinous 0.06 0.01 0.06 0.02 0.48 1.00 0.09 0.05 0.13 0.08 19 Corals 20 Encrusting_inverts 21 Seastars_&_brittlestars 0.04 0.00 22 Echinoids 0.00 23 Holothurians 24 Arthropods 0.15 0.19 0.22 0.38 0.22 0.38 0.39 0.20 0.00 0.00 25 Large_benthic_worms 0.00 0.01 0.00 26 Shelled_megabenthos 0.00 0.00 27 Macrobenthos 0.02 0.01 0.02 0.03 0.24 0.36 0.24 0.00 28 Meiobenthos 0.22 29 Mesozooplankton 0.10 0.29 0.18 0.93 0.41 0.64 0.32 30 Ciliates 0.05 0.22 31 Het_flagellates 0.11 32 Phytoplankton 0.22 0.11 33 Bacteria_water 0.11 34 Bacteria_sediment 35 Carcasses 0.10 0.12 0.07 36 Detritus_water 0.11 37 Detritus_benthic

26 Ecosystem Modelling of the Chatham Rise

Table 7b: Diet parameters in the balanced model of the Chatham Rise showing groups 19-37. Predators are referred to by group number for brevity and this is the same group number shown in column 1. Figures are the proportions of prey by weight of organic carbon in diet of each predator. Predators are shown as columns and prey as rows. Columns sum to 1 for consumers. Entries of “0.00” imply that the diet fraction is >0% and <0.5%.

Predators Prey 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 1 Birds NA NA NA NA 2 Toothed_whales NA NA NA NA 3 Baleen_whales NA NA NA NA 4 Seals NA NA NA NA 5 Hoki NA NA NA NA 6 Orange_roughy NA NA NA NA 7 Oreos NA NA NA NA 8 Warehous NA NA NA NA 9 Large_javelinfish_guild NA NA NA NA 10 Small_javelinfish_guild NA NA NA NA 11 Hake_guild NA NA NA NA 12 Rattails_&_ghost_sharks NA NA NA NA 13 Ling_guild NA NA NA NA 14 Small_demersal_fish NA NA NA NA 15 Mesopelagic_fish NA NA NA NA 16 Cephalopods NA NA NA NA 17 Macrozoo_krill NA NA NA NA 18 Macrozoo_gelatinous NA NA NA NA 19 Corals 0.19 0.00 NA NA NA NA 20 Encrusting_inverts 0.00 0.27 0.03 NA NA NA NA 21 Seastars_&_brittlestars NA NA NA NA 22 Echinoids 0.00 0.02 NA NA NA NA 23 Holothurians NA NA NA NA 24 Arthropods NA NA NA NA 25 Large_benthic_worms 0.00 0.01 NA NA NA NA 26 Shelled_megabenthos 0.00 0.01 NA NA NA NA 27 Macrobenthos 0.25 0.09 0.00 0.50 0.17 0.04 NA NA NA NA 28 Meiobenthos 0.80 0.03 0.20 0.29 0.12 NA NA NA NA 29 Mesozooplankton 0.14 0.29 NA NA NA NA 30 Ciliates 0.06 0.06 NA NA NA NA 31 Het_flagellates 0.06 0.34 0.60 NA NA NA NA 32 Phytoplankton 0.31 0.40 0.54 NA NA NA NA 33 Bacteria_water 0.35 0.50 0.06 0.46 NA NA NA NA 34 Bacteria_sediment 0.36 0.27 0.10 0.41 0.15 0.12 0.42 0.13 NA NA NA NA 35 Carcasses 0.18 NA NA NA NA 36 Detritus_water 0.40 0.50 0.06 NA 1.00 NA NA NA 37 Detritus_benthic 0.36 0.27 0.10 0.41 0.15 0.12 0.42 0.87 NA 1.00 NA NA NA

Ecosystem Modelling of the Chatham Rise 27

3.1.2 Ecosystem structure and function in the balanced model Here we describe the structure of the foodweb of the Chatham Rise as represented in the balanced trophic model. Biomasses of groups in the model varied by 4.3 orders of magnitude, between 2.9 gC m -2 (phytoplankton) and 0.13 mgC m -2 (holothurians). Total net primary production (NPP) in the balanced model was 276 gC m -2 y-1. This was slightly below the mean for 14 large marine ecosystems around the world which support significant large- scale fisheries (encompassing temperate boreal shelves and eastern boundary currents; Conti & Scardi (2010); Figure 2).

Figure 2: Net primary production (NPP) in 14 large marine ecosystems (Conti & Scardi, 2010) compared with that for the Chatham Rise estimated in this study. Ecosystems compared are taken from the Atlantic Ocean (blue bars), Pacific Ocean (green bars) and Eastern Boundary Currents (pink bars).

Of the 276 gC m -2 y-1 net primary production, 46% was directly grazed (30% by heterotrophic flagellates, 13% by mesozooplankton and 3% by ciliates [heterotrophic microzooplankton]). The remaining 53% of phytoplankton NPP entered the detrital pool of the water column (dissolved and particulate detritus) where it was acted on by water column bacteria. Bacterial production in the upper water column was 70 gC m -2 y-1, equivalent to 26% of NPP. The bacterial production was consumed by heterotrophic flagellates, which were in turn consumed by ciliates and mesozooplankton.

In the balanced model, the particulate organic carbon (POC) detrital flux to the seabed (settling “marine snow”) represents an annual transfer of 7.3 gC m -2 y-1, equivalent to 2.6% NPP. The POC flux rate in the balanced model is 3.2 times higher than the POC flux to the benthos of 2.3 gC m -2 y-1 estimated based on short-term (few days) deployments of floating traps over the Chatham Rise (Nodder & Gall, 1998; see Appendix H for details of the estimation of POC flux from local field data and remote sensing products). The transfer of material to the benthos in the balanced model would suggest a mean p-ratio (ratio of the organic flux just below the base of the surface mixed layer to NPP) for the Chatham Rise of

Ecosystem Modelling of the Chatham Rise 28

4.7% rather than the estimated 1.5% in Appendix H. Given that global relationships used to predict p-ratios from sea surface temperature (Lutz et al. 2007) would suggest p-ratios of 3.2% for the Chatham Rise, this is reasonable. POC flux to the seabed may be higher than estimated based on Nodder & Gall (1998) because the episodic and spatially-patchy nature of sediment flux (Nodder & Northcote 2001) means that substantial flux may be missed by short-term deployments of sediment traps.

In the model, POC flux to the seabed of 7.3 gC m -2 y-1 is augmented by 2.9 gC m -2 y-1 of local benthic detrital generation (79% by benthic meiofauna). There is a long-term accumulation of 1.0 gC m -2 y-1 (compared to 1 gC m -2 y-1 proposed in Appendix H). The remaining 9.2 gC m -2 y-1 is consumed by benthic meiofauna (40%) or acted on by benthic bacteria in the sediments (51%). Total respiration by the benthos in the model is 5.7 gC m -2 y-1 (29% due to meiofauna respiration and 57% due to respiration of benthic bacteria). This compares reasonably well with measurements of the sediment community oxygen consumption (SCOC) across the centre of the Chatham Rise (Nodder et al., 2003) which lead to estimates of the total infaunal community respiration rate of 6.8 gCm -2y-1.

Benthic macrofauna in the model take 97% of their food from benthic sources and 3% from the water column. Consumption by megabenthos in the model is dominated by arthropods (98%) with other groups less than 1%. Fishing discards make up 11% of the carcass flux in the model; the majority of the carcasses (89%) are from bodies of other organisms (non- predation mortality).

There were 9 groups of large demersal fishes in the model defined according to individual species or groups of species and 5 trophic guilds based on stomach contents analysis from the Chatham Rise (Dunn et al. submitted; see Appendix D). The groups defined according to guild were hake guild (benthopelagic predators), ling guild (benthic predators), rattails & ghost shark guild (benthic invertebrate feeders), large javelinfish guild (pelagic foragers), and small javelinfish guild (benthopelagic invertebrate feeders). These fish groups in total consumed 0.8 gC m -2 y-1 in the following proportions: hoki (26%), orange roughy (13%), oreos (18%), warehous (8%), large javelinfish guild (4%) and small javelinfish guild (3.%), hake guild (10%), rattails & ghost shark guild (8%) and ling guild (11%). In the balanced model, the food for the demersal fishes was made up largely of middle-trophic level, groups: arthropods (20%), small demersal fishes (18%), gelatinous macrozooplankton (18%), mesopelagic fish (14%), other demersal fishes (10%), cephalopods (8%), other benthic invertebrates (5%), hard-bodied macrozooplankton (4%), carcasses (2%), and mesozooplankton (1%).

Four groups in the model cover the air-breathing predators: seabirds, toothed whales & dolphins, baleen whales and seals. Consumption of these groups combined in the model was equivalent to 0.11 gCm -2y-1, in proportions: seabirds (92%), toothed whales & dolphins (4.6%), seals (3.0%) and baleen whales (0.3%). Seals had the highest trophic level in the model (5.4), close to toothed whales & dolphins (5.3). Seabirds had trophic level of 4.9 and baleen whales of 4.6 reflecting feeding on lower trophic level prey (invertebrates rather than fishes).

Ecosystem Modelling of the Chatham Rise 29

The six middle-trophic level groups in the model were small demersal fishes, mesopelagic fishes, cephalopods, arthropods and hard and soft-bodied macrozooplankton. These groups had trophic level between 2.3 (arthropods) and 4.5 (cephalopods). Total consumption by these groups in the model was 5.7 gCm -2y-1, in proportions mesopelagic fishes (25%), arthropods (22%), gelatinous zooplankton (16%), hard-bodied macrozooplankton (16%), small demersal fishes (12%), and cephalopods (9%). These groups together supply 81% of the prey for demersal fishes. In the balanced model, the four mesopelagic middle-trophic level groups (cephalopods, mesopelagic fish and two macrozooplankton groups) together supply 99% of the prey for air-breathing predators, in proportions mesopelagic fishes (44%), krill (35%), cephalopods (14%) and salps (6%). In the model, the four mesopelagic groups feed principally on mesozooplankton, which supplies 64% of their prey. The remainder of the prey of the four mesopelagic groups is made up from small zooplankton (9%), phytoplankton (8%), other mesopelagic groups (13%) and detritus/bacteria in the water column (5%).

3.1.3 Trophic levels Trophic levels for the balanced model are shown in Table 8. Particular organisms may be expected to have broadly similar trophic levels (TrL) in similar types of ecosystems where they are feeding on similar prey so that comparing trophic levels may be a crude way of highlighting major inconsistencies. Trophic levels for the groups in the Chatham Rise model agree well with those from trophic models elsewhere. However, for birds in the Chatham Rise model, TrL=4.9 is considerably higher than 3.8 (Arreguin-Sanchez et al. 2002) and 4.5 (Jarre-Teichman et al. 1998). Birds in the Chatham Rise are likely to more closely resemble the fish-eating birds of the open ocean Benguela system modelled by Jarre-Teichman et al. (1998) rather than the coastal invertebrate feeders as in the model by Arreguin-Sanchez et al. (2002). Macrobenthos at TrL=2.2 compares with values for crabs and predatory invertebrates: 3.3–3.4 (Wolff 1994) and 2.4–2.8 (Arreguin-Sanchez et al. 2002), and 2.0–2.1 (Jiang & Gibbs 2005). Microzooplankton (ciliates) here have TrL=2.6 compared to values for “zooplankton” of 2.2–2.4 (Jarre-Teichman et al. 1998), 2.0 (Mendoza 1993, Jiang & Gibbs 2005) and 2.2 (Arreguin-Sanchez et al. 2002). Trophic levels for demersal fish groups in the Chatham Rise model at 3.5–5.1 (mean 4.3) are higher than coastal ecosystem studies, for example, 3.3 (Jarre-Teichman et al. 1998), 2.7–3.5 (Wolff 1994), 3.2–3.9 (Mendoza 1993) and 3.1–3.8 (Jiang & Gibbs 2005). Trophic level values for demersal fish in the Chatham Rise model presented here are more similar to the range of for the Chilean upwelling system model of 3.4–5.1 (Neira & Arancibia 2004), and for the Benguela system of 3.5–4.7 (Shannon et al. 2001). Note that trophic levels for fish are very sensitive to the diets of demersal fish in the balanced model. For comparison, Fishbase (Froese & Pauly 2003) gives trophic level of 4.2–4.5 for hoki based on Bulman & Blaber (1986) compared to the model estimate of 4.9. Fishbase (Froese & Pauly 2003) gives trophic level of 4.1–4.3 for orange roughy based on Bulman & Koslow (1992) which is again lower than our estimate of 5.1. Better consideration of diet of demersal fishes in the Chatham Rise model, and especially separating out the highly-aggregated prey species of mesopelagic fishes, hard-bodied macrozooplankton and mesozooplankton, may help to reconcile these differences in the future.

30 Ecosystem Modelling of the Chatham Rise

Table: 8 Output parameters for the Chatham Rise trophic model. The table shows trophic levels, respiration quotients (R/B), trophic importances (TI) by two methods and rank of trophic importance (1=highest).

Group R/B (y -1) Trophic Level TI1 TI2 Rank(TI1) Rank(TI2) 1 Birds 72.4 4.9 0.13 0.09 19 20 2 Toothed_whales 6.5 5.3 0.01 0.01 30 29 3 Baleen_whales 0.4 4.6 0.00 0.00 31 31 4 Seals 14.7 5.4 0.02 0.02 28 28 5 Hoki 1.4 4.6 0.57 0.62 4 3 6 Orange_roughy 1.9 4.7 0.13 0.14 18 19 7 Oreos 1.2 4.1 0.21 0.23 15 16 8 Warehous 2.2 4.2 0.07 0.05 21 23 9 Large_javelinfish_guild 1.6 4.2 0.04 0.04 25 25 10 Small_javelinfish_guild 1.7 3.8 0.03 0.02 27 27 11 Hake_guild 1.3 5.1 0.28 0.47 14 9 12 Rattails_&_ghost_sharks 1.5 3.5 0.39 0.46 9 13 13 Ling_guild 1.2 4.3 0.20 0.26 16 15 14 Small_demersal_fish 2.1 3.5 0.66 0.81 2 2 15 Mesopelagic_fish 4.3 4.1 0.41 0.53 7 7 16 Cephalopods 16.6 4.5 0.36 0.58 11 4 17 Macrozoo_krill 16.2 3.6 0.35 0.46 12 12 18 Macrozoo_gelatinous 2.6 3.2 0.37 0.47 10 8 19 Corals 1.5 2.3 0.05 0.04 23 24 20 Encrusting_inverts 0.8 2.0 0.05 0.06 22 22 21 Seastars_&_brittlestars 1.2 2.5 0.04 0.03 26 26 22 Echinoids 1.2 2.5 0.12 0.18 20 17 23 Holothurians 1.0 2.8 0.00 0.00 32 32 24 Arthropods 2.6 2.3 0.42 0.58 6 5 25 Large_benthic_worms 5.4 2.8 0.01 0.01 29 30 26 Shelled_megabenthos 3.7 2.7 0.05 0.06 24 21 27 Macrobenthos 0.8 2.2 0.34 0.47 13 10 28 Meiobenthos 13.0 2.0 0.40 0.45 8 14 29 Mesozooplankton 29.6 3.0 0.65 1.00 3 1 30 Ciliates 114.4 2.6 0.20 0.14 17 18 31 Het_flagellates 244.8 2.0 0.47 0.53 5 6 32 Phytoplankton NA 1.0 1.00 0.46 1 11 33 Bacteria_water 130 1 NA NA NA NA 34 Bacteria_sediment 2 1 NA NA NA NA 35 Carcasses NA 3.3 NA NA NA NA 36 Detritus_water NA 1 NA NA NA NA 37 Detritus_benthic NA 1 NA NA NA NA

3.1.4 Trophic importances The single step transfer matrix Q for the balanced model is shown in Figure 3. The multiple- step (Mixed Trophic Impact) matrix M is shown in Figure 4. There are strong similarities in the two ways of calculating trophic impact. In both, major negative impacts (top-down predation effects) are toothed whales on toothed whales (because the only predator of the toothed whale group in the model is other toothed whales), rattails & ghost sharks on a range of megabenthic invertebrates, echinoderms on corals, meiobenthos on benthic bacteria,

Ecosystem Modelling of the Chatham Rise 31

mesozooplankton on ciliates, and heterotrophic flagellates on water column bacteria. In the single-step analysis, there are positive (bottom-up, prey driven) effects of the six key middle- trophic level groups (small demersal fishes, arthropods, mesopelagic fish, cephalopods hard- and soft-bodied macrozooplankton) on many demersal fish groups, meiobenthos on holothurians, and mesozooplankton on cephalopods and decapods. Most of these bottom-up (prey-driven) interactions are similar in the multiple-step analysis, but note that the sign of the effect of changes in mesopelagic fish, small demersal fishes and cephalopods on some demersal fish groups changes sign between the single-step and multiple-step analysis. This because these groups have a negative single-step effect on their prey items and this effect is taken into account in the multiple-step analysis.

Despite these differences, the patterns in the trophic importances by the single-step and multiple-step methods are very consistent. The trophic importances of the groups according to the balanced model are shown in Figure 5 (TI1) and Figure 6 (TI2), and given in Table.

Mesozooplankton are crucial to the structure and function of the Chatham Rise ecosystem, having the highest (TI1) or 3rd highest (TI2) trophic importances in the system. This reflects the pivotal role of this group for energy transfer from the lower food web to middle trophic level predators. The multiple-step analysis also highlights the underpinning role of phytoplankton in the system. Phytoplankton are responsible for all initial formation of organic matter in the ecosystem. Of the six middle-trophic level groups, small demersal fishes are identified as being the most trophically important by this analysis. Arthropods and mesopelagic fish also have high importance in the multi-step analysis (TI2), as do cephalopods and hard- and soft-bodied macrozooplankton). The trophic importance analysis based on the balanced model suggests that hoki play a key role in the system (3 rd or 4 th most important group). The fish guild of rattails & ghost sharks is the most important demersal fish guild in the multi-step analysis. The role of the meiobenthos is highlighted by the multistep analysis (TI2), with importance of 8th in the system. Sensitivity of trophic importance to biomass of corals and encrusting invertebrates Because the mid-Chatham rise Benthic Protection Area is poorly represented in terms of DTIS information used to estimate megafaunal biomass in the trophic model, we tested the sensitivity of TI1 and TI2 indices to the biomass of corals and encrusting_inverts in the balanced model. To do this, we increased the initial estimates of the biomass of corals and encrusting_inverts tenfold, rebalanced the model and recalculated the indices of trophic importance, TI1 and TI2 (Figure 5 and Figure 6). The effects of substantially increasing the biomasses of the corals and encrusting_inverts groups on their trophic importances were small: rank trophic importance of corals increased by 3 (single-step, TI1) and 2 (multi-step, TI2); rank trophic importance of encrusting_inverts increased by 5 (single-step, TI1) and 0 (multi-step, TI2). Even with 10 times more biomass of corals and encrusting_inverts in the model, the trophic importances of corals and encrusting_inverts were still in the lower half of model groups.

32 Ecosystem Modelling of the Chatham Rise

Figure 3: Single-step trophic impact matrix, Q, for the Chatham Rise based on the balanced model. Positive impacts are shown white and negative are black, with the diameter of the circle proportional to the magnitude of the effect. The “impact” is interpreted as the effect that a small increase in the biomass of the impacting group (shown on the left of the diagram) may have on the biomass of the impacted group (shown across the top).

Ecosystem Modelling of the Chatham Rise 33

Figure 4: Multiple-step mixed trophic impact matrix, M, for the Chatham Rise. Positive impacts are shown white and negative are black, with the diameter of the circle proportional to the magnitude of the effect.

34 Ecosystem Modelling of the Chatham Rise

Figure 5: Trophic importance TI1 from the ecosystem model of the Chatham Rise shown in descending order of importance. The labels are in equivalent descending order of importance, numbers being their rank importance. TI1 is based on single-step impact matrix (Q), summing by absolute values. The coloured lines show the effect of increasing the biomass of corals (square symbols, red lines) and encrusting_inverts (triangle symbols, green lines) by a factor of 10, rebalancing the model and recalculating the index of trophic importance. This sensitivity analysis was carried out because there were limited data on the biomass of these sessile megafaunal groups available.

Ecosystem Modelling of the Chatham Rise 35

Figure 6: Trophic importance TI2 from the ecosystem model of the Chatham Rise shown in descending order of importance. The labels are in equivalent descending order of importance, numbers being their rank importance. TI2 is based on the multiple-step impact matrix (M), summing by absolute values. The coloured lines show the effect of increasing the biomass of corals (square symbols, red lines) and encrusting_inverts (triangle symbols, green lines) by a factor of 10, rebalancing the model and recalculating the index of trophic importance. This sensitivity analysis was carried out because there were limited data on the biomass of these sessile megafaunal groups available. 4 Discussion & Conclusions 4.1 End-to-end mass-balance models of marine ecosystems are useful for indicating whether data on the various components of the ecosystem function are consistent and for understanding the structural properties of the system. These structural properties are likely to be linked with dynamic (functional) properties such as how one part of the system may respond to changes in another.

4.2 It is important to note that the analysis presented here provides information at one set of scales. The model provides information: (i) at the spatial scale of the whole Chatham Rise; (ii) averaged over an annual period (seasonal dynamics not resolved); (iii) for a “typical” recent year (i.e. between-year variations are not considered); (iv) in a relatively small number of trophic groups (intra-population demographics and particular species not resolved); (v) focus on major flows of energy through the food-web and so little information is provided with regard to minor species; (vi) trophic connections only (provision of habitat, predation- interference effects are not considered).

36 Ecosystem Modelling of the Chatham Rise

4.3 There is a large amount of information available on the food-web of the Chatham Rise; the Chatham Rise is probably the best-studied offshore region within the New Zealand EEZ. Nevertheless, substantial deficits in information remain in all groups. Particularly poorly known groups include cetaceans (numbers of whales in the study area at different times of the year are not known), mesopelagic fishes, and large zooplankton (both gelatinous and hard-bodied macrozooplankton).

4.4 The current version of the Chatham Rise model has included much new information. This has included (i) relative environmental suitability mapping (Kaschner, 2004) to help with estimating order-of-magnitude estimates of cetaceans on the Chatham Rise; (ii) preliminary data from two Fisheries Oceanography II voyages to the Chatham Rise (TAN0806 and TAN1116) on mesopelagic and hyperbenthic biota (Gauthier et al., submitted); (iii) data on the megabenthos and biotic habitats of the Chatham Rise from the Ocean Survey 20-20 project (Bowden, 2011; Hewitt et al. 2011); (iv) information on the macrobenthos, meiobenthos and benthic bacteria from combining the Nodder benthic database with data the Ocean Survey 20-20 project (Nodder et al., 2011); (v) updated remotely-sensed measurements of upper ocean productivity from the 10+ year time series of MODIS-Aqua ocean colour data, including primary production satellite algorithms; (vi) recent feeding guild analysis for demersal fishes on the Chatham Rise (Dunn et al., submitted). However, we note that the mid-Chatham rise Benthic Protection Area is poorly represented in terms of DTIS information used to estimate megafaunal biomass in the trophic model.

4.5 There is more information available now or in the near future for a number of groups. Further development of this model should focus on: (i) inclusion of biomass estimates for encrusting and other benthic invertebrates in the mid Chatham Rise Benthic Protection Area; (ii) improving/updating estimates of biomass, catch, discard rates and energetics of demersal fish groups on the Chatham Rise. Stock sizes of fish in the Chatham Rise can change rapidly (e.g. recent changes in hoki stock), and biomass and catch data used in the model presented here needs to be periodically updated; (iii) more results on the mesopelagic and hyperbenthic biota of the Chatham Rise from the two Fisheries Oceanography II voyages to the Chatham Rise (TAN0806 and TAN1116) are likely to become available in the next few years. These data may allow better resolution of key groups in the mesozooplankton, macrozooplankton, mesopelagic fish, and decapod trophic groups; (iv) consideration of methods to estimate the cryptic biomass of small (sub-net sized) demersal fishes e.g. ratcatcher trawls on the Chatham Rise; (vi) integration of data on sediment community oxygen consumption from the Nodder benthic database and the Ocean Survey 20-20 project (Nodder et al., 2011), and the use of this to constrain the benthic meiofauna/bacterial components of the model. 4.6 Changes to the initial parameter set during balancing were plausible and generally low; mean absolute changes in biomass, productivity and diet parameters were 6.7%, 2.2% and 4.0% respectively. A small number of large parameter changes (>40%) were needed for balance groups for which we have relatively poor information over the Chatham Rise.

4.7 The current version of the Chatham Rise model is unvalidated. Stable isotope data on organisms in a food-web can be useful for model validation (via trophic levels) and to refine poorly-known diets and transfer efficiencies. Carbon isotopes are a powerful tool for identifying primary sources of organic material within ecosystems and showing benthic reworking (Fry & Sherr, 1984; Peterson & Fry, 1987). In a relatively small area like the

Ecosystem Modelling of the Chatham Rise 37

Chatham Rise, variations in δ13 C tend to be low compared to δ15 N variations and may be of limited value except for highly mobile organisms, or those with a mixture of benthic and pelagic feeding. Nitrogen isotope ratios often show distinct enrichments per successive trophic level and have strong applications in food web and dietary studies (DeNiro & Epstein, 1981; Minagawa & Wada, 1984; van der Zanden & Rasmussen, 2001). Together, analysis of carbon and nitrogen stable isotopes have the potential to quantitatively validate food-web models such as that presented here. Large numbers of samples from the Chatham Rise are currently being processed for the stable isotopic composition of carbon and nitrogen. These include midwater and benthic invertebrates (500+ samples), mesopelagic fish (500+ sample), macrobenthic and meiobenthic samples (200 samples), demersal fish (200 samples).

4.8 Trophic models like this are highly unconstrained (more variables than constraints) and hence the balanced model is but one solution of many that may be considered “consistent” with the available data. Further research to explore the effects of parameter uncertainty on the system-level characteristics of the model (including trophic importance) would be useful.

4.9 The net primary production (NPP) of the Chatham Rise (which sets a limit on carrying capacity) is high within the New Zealand-Australian-Subantarctic region, but moderate compared to other regions around the world that support significant large-scale fisheries.

4.10 Most (83%) of NPP is remineralized within the lower pelagic food-web. The main pathways of energy to the middle foodweb include arthropods, small demersal fishes, mesopelagic fishes, squid, krill and salps. These 6 mesopelagic groups provide 82% of the food for demersal fishes and 99% of the food for air-breathing predators.

4.11 In the model, the transfer of organic matter to the benthos by passive settling flux of particulate detrital material is equivalent to 2.6% of NPP (7.3 gC m -2 y-1). An additional 0.2 gC m-2 y-1 is estimated to be supplied to benthic fauna by feeding of benthic biota in the water column. Carcasses (dead bodies of larger organisms) provide an additional 0.1 gC m -2 y-1 to the benthos. These three sources provide all the energy for the benthic communities. For comparison, this energy supply to the benthos is only 20% of the production of mesozooplankton.

4.12 Trophic impact matrices were calculated from the balanced model showing the change in one group due to a small change in another group. “Trophic importance” is defined as effect of one group on all other groups and describes how important a group is to the structure and function of the ecosystem. Small demersal fishes and mesozooplankton were the most ecologically important consumer groups based on the multi-step analysis. Mesopelagic fishes, hoki, and arthropods also had high trophic importances in the multi-step analysis. Benthic meiofauna had relatively high trophic importance (8 th most important in the multi-step analysis). All the megabenthos groups had trophic importances in the lower half of groups in the model. Sensitivity analysis showed that 10 fold increases in the biomass of corals and encrusting_inverts led to only small increases in their trophic importances. 5 Acknowledgements Previous versions of trophic modelling of the Chatham Rise were supported by the Foundation for Science Research and Technology under Coasts and Oceans OBI (C01X0501), and by core funding from the New Zealand Ministry of Business, Innovation and Employment (MBIE). Two Fisheries Oceanography voyages to the Chatham Rise were

38 Ecosystem Modelling of the Chatham Rise

funded by core funding from MBIE, with assistance from scientists from the University of British Columbia (Vancouver, Canada), University of Western Australia (Sydney), and the New Zealand Universities of Auckland, Waikato and Otago. The OS20-20 surveys were funded by the New Zealand Government, Land Information New Zealand, Ministry of Fisheries, NIWA and Department of Conservation (DoC). OS20-20 post-voyage analyses were funded by the Cross-Departmental Research Pool; additional funds were also provided by DoC. Remotely-sensed ocean colour and SST data are used courtesy of NASA/Goddard Space Flight Center. We gratefully acknowledge help from David Bowden, Janet Bradford- Grieve, Scott Nodder, Suze Baird, Arne Pallentin, Sanjay Wadhwa, Julie Hall, David Thompson, Leigh Torres, Darren Stevens, Jeff Forman, Neil Bagley, and Richard O’Driscoll (all NIWA) in the preparation of this report. 6 References Arreguin-Sanchez, F.; Arcos, E.; Chavez, E.A. (2002). Flows of biomass and structure in an exploited benthic ecosystem in the Gulf of California, Mexico. Ecological Modelling 156: 167–183.

Banse, K., English, D.C. (1997). Near-surface phytoplankton pigment from the Coastal Zone Color Scanner in the Subantarctic region southeast of New Zealand. Marine Ecology-Progress Series 156: 51-66.

Banse, K., Mosher, S. (1980). Adult body size and annual production / biomass relationships of field populations. Ecological Monographs, 50: 355-379.

Behrenfeld, M.J., Falkowski, P.G. (1997). Photosynthetic rates derived from satellite-based chlorophyll concentration. Limnology and Oceanography, 42: 1- 20.

Behrenfeld, M.J.;, Maranon, E.; Siegel, D.A.; Hooker, S.B. (2002). Photoacclimation and nutrient-based model of light-saturated photosynthesis for quantifying oceanic primary production. Marine Ecology Progress Series, 228: 103-117.

Belkin, I.M. (1988). Main hydrological features of the central part of the Pacific Sector of the Southern Ocean. In: Vinogradov, M. E.; Flint, M. V. ed. Pacific subantarctic ecosystems. Moscow, Nauka (English translation). Pp. 12-17.

Bowden, D.A. (2011). Benthic invertebrate samples and data from the Ocean Survey 20/20 voyages to the Chatham Rise and Challenger Plateau, 2007. New Zealand Aquatic Environment and Biodiversity Report No. 65.

Boyd, P.; LaRoche, J.; Gall, M.; Frew, R.; McKay, R.M.L. (1999). The role of iron, light and silicate in controlling algal biomass in sub-Antarctic water SE of New Zealand. Journal of Geophysical Research, 104(C6): 13395-13408.

Bradford-Grieve, J.M.; Boyd, P.W.; Chang, F.H.; Chiswell, S.; Hadfield, M.; Hall, J.A.; James, M.R.; Nodder, S.D.; Shushkina, E.A. (1999). Pelagic ecosystem structure and functioning in the Subtropcial Front region east of New Zealand in Austral winter and spring 1993. Journal of Plankton Research, 41(1): 405-428.

Ecosystem Modelling of the Chatham Rise 39

Bradford-Grieve, J.M.; Probert, P.K.; Nodder, S.D.; Thompson, D.; Hall, J.; Hanchet, S.; Boyd, P.; Zeldis, J.; Baker, A.N.; Best, H.A.; Broekhuizen, N.; Childerhouse, S.; Clark, M.; Hadfield, M.; Safi, K.; Wilkinson, I. (2003). Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology, 289: 223-262.

Bradford-Grieve, J.M.; Murdoch, R.; James, M.; Oliver, M; McLeod, J. (1998). Mesozooplankton biomass, composition, and potential grazing pressure on phytoplankton during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand. Deep-Sea Research I, 45: 1709–1737.

Bulman, C.M.; Koslow, J.A. (1992). Diet and food consumption of a deep-sea fish, orange roughy Hoplostethus atlanticus (Pisces: Trachichthyidae), off southern eastern Australia. Marine Ecology Progress Series, 8: 115-129.

Chiswell, S.M. (1994). Acoustic Doppler Current Profiler measurements in the Subtropical Convergence over the Chatham Rise. New Zealand Journal of Marine and Freshwater Research 28: 167–178.

Christensen, V.; Walters, C.J.; Pauly, D.; Forrest, R. (2008). Ecopath with Ecosim Version 6: user guide. Vancouver, Canada, Fisheries Centre, University of British Columbia.

Christensen, V.; Walters, C.J.; Pauly, D. (2000). Ecopath with Ecosim: a user’s guide. University of British Columbia, Fisheries Centre, Vancouver, Canada and ICLARM, Penang, Malaysia, 125 pp. [draft available at www.ecopath.org/]

Christensen, V.; Pauly, D. (1992). The ECOPATH II - a software for balancing steady-state ecosystem models and calculating network characteristics. Ecological Modelling 61:169-185.

Christensen, V.; Walters, C.J. (2004). Ecopath with Ecosim: methods, capabilities and limitations. Ecological Modeling, 172: 109-139.

Conti, L.; Scardi, M. (2010). Fisheries yield and primary productivity in large marine ecosystems. Marine Ecology Progress Series, 410: 233-244.

DeNiro, M.J.; Epstein, S. (1981). Influence of diet on the distribution of nitrogen isotopes in animals. Geochimica et Cosmochimica Acta, 45: 341-351.

Dunn, M.R.; Horn, P.L.; Pinkerton, M.H. (submitted, 2013). Guild structure and biomass trends in a deep water fish assemblage. PLoS One.

Froese, R.; Pauly, D. (editors) (2003). FishBase. World Wide Web electronic publication. www.fishbase.org, version 10 December 2003

Fry, B.; Sherr, E.B. (1984). δ13C measurements as indicators of carbon flow in marine and freshwater systems. Contributions in Marine Science, 27: 13–47.

40 Ecosystem Modelling of the Chatham Rise

Gauthier, S.; Oeffner, J.; O’Driscoll, R.L. (2013). Species composition and acoustic signatures of mesopelagic organisms in a subtropical convergence zone, the New Zealand Chatham Rise. Submitted to PLoS One.

Gordon, A.L.; Baker, T.N.; Molinelli, E.J. (1986). Southern Ocean Atlas. New York, Columbia University Press.

Hall, J.A., James, M.R., Bradford-Grieve, J.M. (1999). Structure and synamics of the pelagic microbial food web of the Subtropical Convergence region east of New Zealand. Aquatic Microbial Ecology, 20: 95-105.

Heath, R.A. (1976). Models of the diffusive-advective balance at the Subtropical Convergence. Deep-Sea Research, 28: 1153-1164.

Hewitt, J.; Julian, K.; Bone, E.K. (2011). Chatham–Challenger Ocean Survey 20/20 Post-Voyage Analyses: Objective 10 – Biotic habitats and their sensitivity to physical disturbance. New Zealand Aquatic Environment and Biodiversity Report No. 81.

Jarre-Teichmann, A.; Shannon, L.J.; Moloney, C.L.; Wickens, P.A., (1998). Comparing trophic flows in the southern Benguela to those in other upwelling ecosystems. South Africal Journal of Marine Science, 19: 391-414.

Jiang, W.; Gibbs, M.T. (2005). Predicting the carrying capacity of bivalve shellfish culture using a steady, linear food web model. Aquaculture, 244: 171–185.

Kaschner, K. (2004). Modelling and Mapping Resource Overlap between Marine Mammals and Fisheries on a Global Scale. PhD thesis. The University of British Columbia, Canada.

Kavanagh, P.; Newlands, N.; Christensen, V.; Pauly, D. (2004). Automated parameter optimization for Ecopath ecosystem models. Ecological Modelling, 172(2-4): 141-149.

Libralato, S.; Christensen, V.; Pauly, D. (2006). A method for identifying keystone species in food web models. Ecological Modelling, 195: 153-171.

Lindeman, R.L. (1942). The trophic-dynamic aspect of ecology. Ecology, 23(4):399- 418.

Livingston, M.E.; Clark, M.R.; Baird, S.-J. (2003). Trends in incidental catch of major fisheries on the Chatham Rise for fishing years 1989-90 to 1998-99. NZ Fisheries Assessment Report 2003/52, pp74.

Lorz, A.-N. (2010). Biodiversity of an unknown New Zealand habitat: bathyal invertebrate assemblages in the benthic boundary layer. Marine Biodiversity DOI: 10.1007/s12526-010-0064-x.

Lutz, M.J.; Caldeira, K.; Dunbar, R.B.; Behrenfeld, M.J. (2007). Seasonal rhythms of net primary production and particulate organic carbon flux to depth describe the efficiency of biological pump in the global ocean, Journal of Geophysical Research, 112: C10011, doi:10.1029/2006JC003706.

Ecosystem Modelling of the Chatham Rise 41

McCann, K.; Hastings, A.; Huxel., G.R. (1998). Weak trophic interactions and the balance of nature. Nature, 395: 794-798.

McCann, K.S. (2000). The diversity-stability debate. Nature, 405: 228-233.

McClatchie, S.; Dunford, A. (2003). Estimated biomass of vertically migrating fish mesopelagic fish off New Zealand. Deep-Sea Research I, 50: 1263-1281.

Mendoza, J.J. (1993). A preliminary biomass budget for the northeastern Venezuela shelf ecosystem. In: Christensen, V.; Pauly, D., (Eds) Trophic models of aquatic ecosystems. ICLARM Conference Proceedings, 26: 285-297.

Minagawa, M.; Wada, E. (1984). Stepwise enrichment of 15N along food chains: Further evidence and the relation between δ15N and animal age. Geochimica et Cosmochimica Acta, 48: 1135–1140.

Murphy, R.J.; Pinkerton, M.H.; Richardson, K.M.; Bradford-Grieve, J.M.; Boyd, P.W. (2001). Phytoplankton distribution around New Zealand derived from SeaWiFS data. New Zealand Journal of Marine and Freshwater Research, 35: 343-362.

Neira, S.; Arancibia, H. (2004). Trophic interactions and community structure in the upwelling system off Central Chile (33-39°S). Journal of Experimental Marine Biology and Ecology, 312: 349-366.

Nodder, S.; Maas, E.; Bowden, D.; Pilditch, C. (2011). Physical, biogeochemical, and microbial characteristics of sediment samples from the Chatham Rise and Challenger Plateau. New Zealand Aquatic Environment and Biodiversity Report No. 70.

Nodder, S.D.; Gall, M. (1998). Pigment fluxes in the Subtropical Convergence region, east of New Zealand: relationships to planktonic community structure. New Zealand Journal of Marine and Freshwater Research, 32: 441-465.

Nodder, S.D.; Northcote, L.C. (2001). Episodic particulate fluxes at southern temperate mid-latitudes (41-42oS), in the Subtropical Front region east of New Zealand. Deep-Sea Research part I, 48: 833-864.

O’Driscoll, R.L.; Gauthier, S.; Devine, J.A. (2009). Acoustic estimates of mesopelagic fish: as clear as day and night? ICES Journal of Marine Science, 66: 1310–1317.

Palomares, M.L.; Pauly, D. (1998). Predicting food consumption of fish populations as functions of mortality, food type, morphometrics, temperature and salinity. Marine and Freshwater Research, 49: 447-453.

Peterson, B.J.; Fry, B. (1987). Stable isotopes in ecosystem studies. Annual Review of Ecological Systems, 18: 293–320.

Pinkerton, M.H. (2011a). A balanced trophic model of the Chatham Rise, New Zealand. Unpublished research report for Coasts & Oceans OBI. NIWA, Wellington. Pp. 60.

42 Ecosystem Modelling of the Chatham Rise

Pinkerton, M.H. (2011b). Ecosystem modelling of the present day and historical periods. Final Research Report for Ministry of Fisheries project ZBD200501, “Long-term Change in New Zealand Coastal Ecosystems”. Pp 113. Includes 10 Appendices.

Pinkerton, M.H. (2008). Preliminary trophic model of the Chatham Rise. Unpublished report for Coasts and Oceans OBI. NIWA, Wellington. Pp. 49.

Pinkerton, M.H.; Bradford-Grieve, J.M.; Hanchet, S.M. (2010). A balanced model of the food web of the Ross Sea, Antarctica. CCAMLR Science, 17: 1–31.

Pinnegar, J.K.; Blanchard, J.L.; MacKinson, S.; Scott, R.D.; Duplisea, D.E. (2005). Aggregation and removal of weak-links in foodweb models: system stability and recovery from disturbance. Ecological Modelling,184: 229-248.

Plagányi, E.P. (2007). Models for an ecosystem approach to fisheries. FAO Fish. Tech. Pap., 477, FAO, Rome (Italy).

Power, M.E.; Tilman, D.; Estes, J.A.; Menge, B.A.; Bond, W.J.; Mills, L.S.; Daily, G.; Castilla, J.C.; Lubchenco, J.; Paine, R.T. (1996). Challenges in the quest for keystones. Bioscience, 46: 609-620.

Press, W.H.; Teukolsky, S.A.; Vetterling, W.T.; Flannery, B.P. (1992). Linear Programming and the Simplex Method. Numerical Recipes in C, Second Edition, Cambridge University Press, 430-444.

Probert, P.K.; Grove, S.L.; McKnight, D.G.; Read, G.B. (1996). Polychaete distribution on the Chatham Rise, Southwest Pacific. Internationale Revue der gesamten Hydrobiologie, 80: 577–588.

Safi, K.A.; Hall, J.A. (1999). Mixotrophic and heterotrophic nanoflagellate grazing in the convergence zone east of New Zealand. Aquatic Microbial Ecology, 20: 83- 93.

Smith, R.; Hall, J.A. (1997). Bacterial abundance and production in different water masses around South Island, New Zealand. New Zealand Journal of Marine and Freshwater Research 31(4): 515–524.

Stanton, B.R. (1997). Sea level and sea surface temperature variability at the Chatham Islands, New Zealand. New Zealand Journal of Marine and Freshwater Research, 31(4): 525–536.

Sutton, P. (2001). Detailed structure of the Subtropical Front over Chatham Rise, east of New Zealand. Journal of Geophysical Research 106 (C12), 31045-31056.

Taylor, G.A., (2000a). Action Plan for Seabird Conservation in New Zealand. Part A: Threatened Seabirds. Threatened Species Occasional Publication 16. 234 p. (Available from: http://www.doc.govt.nz/Publications/004~Science-and- Research/Biodiversity-Recovery-Unit).

Ecosystem Modelling of the Chatham Rise 43

Taylor, G.A., (2000b). Action Plan for Seabird Conservation in New Zealand. Part B: Non-Threatened Seabirds. Threatened Species Occasional Publication 17. 201 p. (Available from: http://www.doc.govt.nz/Publications/004~Science-and- Research/Biodiversity-Recovery-Unit).

Uddstrom, M.J.; Oien, N.A. (1999). On the use of high-resolution satellite data to describe the spatial and temporal variability of sea surface temperatures in the New Zealand region. Journal of Geophysical Research, 104(C9): 20729-20751.

Ulanowicz, R.E.; Puccia, C.J. (1990). Mixed trophic impacts in Ecosystems. Coenoses, 5: 7-16.

Van der Zanden, M.J.; Rasmussen, J.B. (2001). Variation in δ15N and δ13C trophic fractionation: implications for aquatic food web studies. Limnology and Oceanography, 46: 2061–2066.

Wolff, M., (1994). A trophic study for Tongoy Bay – a system exposed to suspended scallop culture (Northern Chile). Journal of Experimental Marine Biology and Ecology, 182: 149-168.

44 Ecosystem Modelling of the Chatham Rise

Appendix A Birds

Introduction More than 70 species of birds are present in the Chatham Rise ecosystem, including species that are unique to the study region (e.g. Chatham Island taiko, Pterodroma magentae ), and many that have declining populations to the point of being endangered species (e.g. Chatham albatross, Thalassarche eremita ) – see Table A1. In this work, we consider all birds in the Chatham Rise ecosystem in one trophic group. Taylor (2000a, b) give a summary of the abundance of New Zealand seabirds, divided into two groups: those that are considered threatened by the International Union for Conservation of Nature and Natural Resources (IUCN) criteria (taxa listed as Critical, Endangered or Vulnerable), and non-threatened species.

Biomass For birds which breed in the study area and have breeding colonies accessible to study, we used censuses of the breeding colonies to estimate breeding pairs (Taylor 2000a, b). The average uncertainty in the number of pairs of birds based on most recent surveys (generally since 1997) was ~20%, but for some species may be >80% (Taylor 2000a, b). In order to estimate the total population size from breeding numbers it is necessary to estimate the number of non-breeding adults and juveniles typically absent from the breeding colony but present in the study area. Non-breeding individuals are likely to comprise between 0.3 and 0.6 of the population depending on species (Taylor 2000a, b). Average bird weights were taken from Heather & Robertson (1996). Most of the species do not live or feed exclusively within the Chatham Rise ecosystem, and to estimate bird biomass and consumption from the system it was necessary to estimate the proportion of the life of each species that can be considered to take place wholly within the study area. These estimates were based on published information on the foraging extent of the bird, and an estimate of the times spent within the study region per year. There is some variability in the level of accuracy in these estimates and some variability from year to year, but best available data was used in each case. We further reduced the bird biomass and amount of food required from the system by F for those species that feed from terrestrial rather as well as marine sources (e.g. gulls, Larus dominicanus dominicanus , L. scopulinus ). The parameters were combined to estimate biomass as equation A1.

NWCF S  M  B =    [A1] A 100  12 

B = average annual biomass density (gC m -2) N = number of birds in the study area W = average weight of bird (gWW [wet-weight]) C = carbon:wet weight ratio (gC/gWW) F = proportion of food from marine sources (dimensionless) A = area of study region (m 2) S = proportion of foraging area covered by the study region (%) M = months spent in the study area per year

Ecosystem Modelling of the Chatham Rise 45

Estimates of the proportions of life spent within the study region ranged from 1 for locally feeding birds resident in the Chatham Rise region (e.g. Pitt Island shag, Stictocarbo featherstoni ), to <0.02 for widely distributed seabirds (e.g. Sooty Shearwater, Puffinus griseus ). The total biomass estimates of seabirds on the Chatham Rise were 729 t (threatened species) and 1630 t (non-threatened). Seabirds classified as “vulnerable” made up about half the species in the study region, but only 31% of the bird biomass, and 21% of the consumption requirements. Seabirds classified as vulnerable include (in order of decreasing biomass): Thalassarche steadi , T. platei , Eudyptes sclateri , Puffinus huttoni, and Thalassarche impavida and Procellaria aequinoctalis. Six species of albatross each constitute more than 1% of the bird biomass of the Chatham Rise. The non-threatened seabird biomass was dominated by Puffinus griseus, Larus dominicanus dominicanus, Pachyptila vittata , and Pterodroma nigripennis . We assume that C=0.10 (i.e. 10% of wet weight of seabirds is carbon, Vinogradov 1953) following previous trophic modelling work (e.g., Bradford-Grieve et al. 2003).

Production Production of marine birds is generally not one of the most important parameters for a trophic model, as seabirds tend to have few direct predators and their biomass is very low compared to other sources of carcasses. For all species we first assumed that the populations are in approximately steady state, i.e. that the populations are neither increasing nor decreasing between years on average. We calculated the annual mortality rate of adults and juveniles, based on species lifespan as follows. Lifespan of birds is positively correlated related to maximum adult weight (Speakman 2005; Prinzinger 1993). “Lifespan” here is the maximum age at death of a (relatively small) sample of measured birds. Speakman (2005) notes that sample size from which lifespan has been estimated is not known for most species of birds, and may be of the order of 100 birds (assumed here), but could be more if non-remarkable lifespans are discarded. Here, we use an average of the regressions of Speakman (2005) and Prinzinger (1993) (which differ by ca. 11–30%) to estimate lifespan from asymptotic adult weights. Age at fledging is estimated as the average of three regressions (Carrier & Auriemma 1992; Weathers 1992; Westmoreland et al. 1986).

Then, we estimated production of species that breed in the area and species that do not breed in the area separately as follows. For species that breed in the area, the net import of live birds is likely to be close to zero. For species with a seasonally-varying population (i.e. ones that undergo migrations into and out of the study area at different times of the year), this is equivalent to assuming that the same weight of live birds enters the study area as leaves it. In this case, production is equal to mortality. We estimated production as the sum of two factors: (1) death of adult and juvenile (post-fledging) birds of near adult weight; (2) death of eggs and chicks. The number of eggs laid per pair varies by species (taken from Heather & Robertson, 1996) is commonly 1 (petrels, terns, shearwaters, penguins), 2 (oyster catchers, gulls) or 3 (shags, herons). For breeding populations, the chick mortality is estimated as the difference between the number of eggs (calculated as number of breeding pairs multiplied by the average number of eggs per pair), and the number of fledglings needed to replace adult mortality each year. The number of chicks dying in a year is converted to a weight assuming the average weight at death is approximately one third adult weight. For species that do not breed in the study area, we calculated the number of birds arriving and departing based on average numbers present (from census and observer data

46 Ecosystem Modelling of the Chatham Rise

as explained above) and the number of birds dying in the study region. Estimated P/B values are between 0.09–0.54 y-1 with a group average of 0.29 y -1. This is higher than production rates for seabirds estimated by some previous studies. For example, Wolff (1994) used 0.07 y-1 for northern Chile seabirds, Brando et al. (2004) used 0.04 y-1 for Italian cormorants, and Crawford et al. (1991) used P/B=0.20 y -1 for southwest African seabirds. The value estimated here for the Chatham Rise is slightly less than that suggested by Bradford-Grieve et al. (2003) of P/B=0.30 y-1 for seabirds of the Southern Plateau.

Consumption Food consumption requirements for each species were estimated by two methods. Nagy (1987) estimated daily dry weight food consumption for seabirds according to body weight. This was converted to carbon using a ratio of 0.4 gC gWW -1 (Vinogradov 1953). In the second method, average daily energy requirement of seabirds was taken as 2.8 the standard metabolic rate (SMR: Lasiewski and Dawson 1967). An assimilation efficiency of 0.75 and energy/carbon ratio of 12.5 kcal gC -1 were used to give carbon requirements (Croxall 1987; Lasiewski & Dawson 1967; Schneider & Hunt 1982). We assumed an average factor of 0.108 gC/g wet wgt for squid, macrozooplankton, and fish (Schneider & Hunt 1982). These methods differed by less than 15% for all bird species, and the results of the two methods were averaged. Food requirements for individual species were then summed in proportions equal to their contribution to total bird biomass. No consumption of food from the Chatham Rise ecosystem was taken to occur when the bird migrated outside the study region. The annual Q/B values for the bird group is 104 y -1 respectively, comparable but larger than previous work (e.g. 62 y -1 for northern Chile seabirds: Wolff 1994; 36.5 y -1 for the Southern Plateau, Bradford-Grieve et al. 2003).

Diet The diet of seabirds is taken to be composed of squid, macrozooplankton (crustacea), and fish (mainly small midwater fish) (Croxall 1987). Albatross feed on fish, squid, and macrozooplankton mainly taken from the ocean surface with some shallow plunging. Some carrion, such as small seabirds, may also be taken (Heather & Robertson 1996). Diet of petrels is reported as cephalopods, crustaceans (especially macrozooplankton), and small fish, taken principally by dipping, surface-seizing, surface-diving, and pursuit diving. Skua prey on eggs and young of breeding birds near the coast, as well as feeding on small midwater fish, and macrozooplankton by surface feeding (Mund & Miller 1995). Skua can also take seal remains and parts of other carcasses. We estimate an initial diet for the bird component of the Chatham Rise model as 46% midwater fish (mainly myctophids but also juvenile fishes), 10% squid and 44% macro- and meso-zooplankton (including gelatinous plankton).

Other information: P/Q, EE, U, accumulation, imports, exports, transfers The values for production and consumption given by the methods explained above lead to overall gross transfer efficiencies (P/Q) of 0.28% (range 0.17–0.50%). This is of a similar magnitude to that used in other models (e.g. Pinkerton et al. 2010, P/Q for flying birds of 0.48%).

Export and import of material can occur from a number of source: (1) export from the system due to birds on average having a different weight when leaving the study area than when entering; (2) mortality of birds occurring over terrestrial habitat or over marine habitat outside

Ecosystem Modelling of the Chatham Rise 47

of the study area; (3) different number of birds entering the study area than leaving it over a year, corrected for differences in their weight. Export by changes in weights of birds was assumed to be close to zero for the study region.

The proportion of mortality that is due to direct predation (i.e. ecotrophic efficiency) is estimated to be close to zero as the majority of mortality is assumed to be bird death due to non-predation causes such as starvation. The proportion of the mortality occurring over land or otherwise outside the study area is accounted for in the adjustment of biomass. All mortality will hence enter the marine part of the study area as bird carcasses, to be consumed by scavengers or degraded by bacterial action.

The impacts of fishing on marine birds are many, but generally not systematically observed (Tasker et al. 2000; Taylor 2000a, b). Birds are incidentally killed by fisheries activities, by collision with lines or other parts of the ship, entanglement in nets, and ensnarement on hooks. Birds can also become entangled in lost fishing gear, disturbed by fishing activity, or affected by pollution from fishing vessels. Discarded material (e.g. offal, discarded bycatch) from fishing vessels may positively impact some seabird species (e.g. James & Stahl 2000). As all birds killed by interactions with fisheries remain local, there is no removal of bird biomass from the ecosystem by fishing vessels and these effects do not impact the model described here.

Jackson (1986) measured mean assimilation efficiencies (AE) of five white-chinned petrel (Procellaria aequinoctialis) fledglings fed on light-fish ( Maurolicus muelleri ), squid ( Loligo reynaudi ) and Antarctic krill ( Euphausia superba ). AE were found for these prey items to be (respectively) 67.5–77.9%. Here, we use 0.3 as the proportion of unassimilated food (U=1- AE) for all bird groups, in line with Pinkerton et al. (2010) but up from U=0.2 for birds used by Pinkerton et al. (2008)

48 Ecosystem Modelling of the Chatham Rise

Summary of data

Table A1: Data and parameters for the birds component of the Chatham Rise trophic model (arranged by alphabetical scientific name)

Threatened/ Area Months Food Non- No. Individual factor, S factor from Eggs/ P/B Q/B Scientific name Common name Breeding area(s) threatened pairs No. birds weight (kg) (%) (months) marine Biomass pair (y -1) (y -1)

Catharacta antarctica (skua) lonnbergi Brown skua Various non-th 360 1450 1.81 10 12 0.5 0.1 2 0.25 75 Catharacta antarctica (skua) lonnbergi Brown skua Chatham Is. non-th 85 345 1.81 50 12 0.5 0.2 2 0.34 75 Daption capense australe Snares cape pigeon Various non-th 7500 32500 0.45 13 12 1 1.8 1 0.33 113 Diomedea antipodensis Antipodean albatross Antipodes/Campbell Is. th 5150 33000 6.50 20 12 1 42.9 1 0.10 52 Diomedea epomophora Southern royal albatross Auckland/Campbell Is. th 8400 50000 9.00 10 8 1 30.0 1 0.09 48 Diomedea gibsoni Gibson's albatross Auckland Is. th 6121.5 40000 6.50 5 12 1 13.0 1 0.10 52 Diomedea sandfordi Northern royal albatross Chatham Is. th 6750 20000 9.00 10 8 1 12.0 1 0.18 48 Eudyptula minor chathamensis Chatham Island blue penguin Chatham Is. non-th 7500 32500 1.10 100 12 1 35.7 2 0.34 87 Fregetta tropica tropica Black-bellied storm petrel Auckland Is. non-th 75000 324996 0.06 5 12 1 0.9 1 0.49 206 Larus bulleri Black billed gull Inland South Island th 33500 140720 0.28 10 12 0.5 1.9 2 0.36 130 Larus dominicanus dominicanus Southern black backed gull Various inc Chatham Is. non-th 700000 2899955 0.95 14 12 0.5 187.1 2.5 0.30 91 Larus scopulinus Red billed gull Various inc Chatham Is. non-th 40000 168024 0.28 10 12 0.5 2.4 2 0.37 129 Leucocarbo onslowi Chatham Island shag Chatham Is. th 842 3537 2.25 100 12 1 8.0 1.5 0.28 71 Macronectes halli Northern giant petrel Various non-th 540 2268 4.50 10 12 1 1.0 1 0.21 58 Macronectes halli Northern giant petrel Chatham Is. non-th 2000 8401 4.50 20 12 1 7.6 1 0.22 58 Morus serrator Australasian gannet Mainland non-th 46004 193245 2.30 14 12 1 60.4 1 0.24 70 Oceanites nereis Grey backed storm petrel Chatham Is. non-th 11000 44999 0.04 100 12 1 1.6 1 0.54 234 Oceanites nereis Grey backed storm petrel Various non-th 25000 114999 0.04 17 12 1 0.7 1 0.54 234 Pachyptila crassirostris crassirostris Fulmar prion Chatham islands th 3000 14000 0.14 100 12 1 2.0 1 0.41 157 Pachyptila crassirostris crassirostris Fulmar prion Snares/Bounty Is. th 29354 123305 0.14 17 12 1 2.9 1 0.41 157 Pachyptila crassirostris eatoni Lesser fulmar prion Auckland Is. th 4000 18000 0.10 17 12 1 0.3 1 0.44 173 Pachyptila desolata Antarctic prion Auckland Is. non-th 550000 2649993 0.15 0 12 1 0.0 1 0.41 144 Pachyptila turtur Fairy prion Various non-th 1000000 4200608 0.13 0 12 1 0.0 1 0.42 152

49 Ecosystem Modelling of the Chatham Rise

Pachyptila turtur Fairy prion Chatham Is. non-th 40000 168024 0.13 100 12 1 21.0 1 0.42 163 Pachyptila vittata Broad billed prion Various non-th 385000 1824993 0.20 30 9 1 82.1 1 0.39 142 Pachyptila vittata Broad billed prion Chatham Is. non-th 330000 1386201 0.20 100 9 1 207.9 1 0.39 142 Pelacanoides urinatrix chathamensis Southern diving petrel Various non-th 468000 2239993 0.13 0 12 1 0.0 1 0.42 150 Pelacanoides urinatrix chathamensis Southern diving petrel Chatham Is. non-th 164000 688900 0.13 100 12 1 89.6 1 0.42 161 Pelacanoides urinatrix exsul Subantarctic diving petrel Auckland/Campbell/Antipodes Is. non-th 550000 2649993 0.13 5 12 1 17.2 1 0.42 161 Pelagogroma marina maoriana NZ white faced storm petrel Various non-th 260000 1139988 0.05 14 5 1 2.9 1 0.51 218 Pelagogroma marina maoriana NZ white faced storm petrel Chatham Is. non-th 840000 3528511 0.05 100 5 1 66.2 1 0.51 218 Phalacrocorax carbo novaehollandiae Black shag Mainland/Chatham Is. non-th 7500 32500 2.20 6 12 1 4.5 3 0.26 71 Phalacrocorax melanoleucos brevirostris Little shag Mainland/Chatham Is. non-th 10000 42006 0.70 6 12 1 1.8 4 0.32 99 Phoebetria palpebrata Light-mantled albatross Auckland/Campbell/Antipodes Is. th 7600 31925 2.75 10 6 1 4.4 1 0.12 67 Procellaria aequinoctalis White-chinned petrel Auckland/Campbell/Antipodes Is. th 210000 882128 1.25 5 12 1 55.1 1 0.27 84 Procellaria cinerea Grey petrel Campbell/Antipodes Is. th 2000 8401 1.00 10 12 1 0.8 1 0.28 90

Procellaria westlandica Westland petrel Westland th 2000 8500 1.10 20 10 1 1.6 1 0.28 87 Pterodroma axillaris Chatham petrel Chatham Is. th Not known 1000 0.20 50 10 1 0.1 1 0.39 142 Pterodroma inexpecta Mottled petrel Mainland South Island/various non-th 30000 139999 0.33 20 9 1 6.8 1 0.35 124 Pterodroma lessonii White headed petrel Antipodes/Auckland Is. non-th 228150 958369 0.60 17 12 1 95.8 1 0.31 104 Pterodroma macroptera gouldi Grey faced petrel North Island mainland non-th 250000 1049985 0.55 10 12 1 57.7 1 0.32 106 Pterodroma magentae Chatham Island taiko Chatham Is. th Not known 150 0.48 50 8 1 0.0 1 0.33 111 Pterodroma mollis mollis Soft plumed petrel Antipodes Is. non-th 75 325 0.30 5 12 1 0.0 1 0.36 126 Pterodroma nigripennis Black-winged petrel Various inc Chatham Is. non-th 2803000 11711827 0.18 10 9 1 153.7 1 0.40 148 Puffinus assimilis elegans Subantarctic little shearwater Antipodes (minor Chatham Is.) non-th 100000 420061 0.20 10 12 1 8.4 1 0.39 142 Puffinus carneipes Flesh-footed shearwater Cook strait non-th 37500 162498 0.60 7 6 1 3.2 1 0.31 104 Puffinus gavia Fluttering shearwater Cook strait non-th 550000 2649993 0.30 7 12 1 53.0 1 0.36 126 Puffinus griseus Sooty shearwater Various non-th 4680000 19658847 0.80 2 12 1 314.5 1 0.29 95 Puffinus griseus Sooty shearwater Chatham Is. non-th 320000 1344195 0.80 10 12 1 107.5 1 0.29 95 Puffinus huttoni Hutton's shearwater Kaikoura th 94000 394857 0.35 80 7 1 64.5 1 0.35 121 Sterna albostriata Black fronted tern South Island mainland th 3000 14000 0.08 38 8 1 0.3 2 0.46 185 Sterna caspia Caspian tern Mainland non-th 1000 4201 0.70 14 12 1 0.4 2 0.30 99 Sterna striata aucklandorna Southern white-fronted tern Chatham Is. th 150 630 0.16 100 12 1 0.1 1 0.40 151 Sterna striata striata New Zealand white-fronted tern Mainland th 13500 55499 0.16 14 9 1 0.9 1 0.40 151

50 Ecosystem Modelling of the Chatham Rise

Auckland/Campbell/Antipodes/Bounty Sterna vittata bethunei Antarctic tern Is. th 1000 4201 0.14 14 12 1 0.1 1 0.41 157 Stictocarbo featherstoni Pitt Island shag Chatham Is. th 669 2810 1.20 100 12 1 3.4 3 0.43 85 Thalassarche (platei) nov. sp. Pacific Northern Buller's Albatross Chatham Is. th 18670 74699 3.00 50 9 1 84.0 1 0.16 65 Thalassarche bulleri Bullers albatross Snares/Solander th 11500 48307 3.00 20 12 1 29.0 1 0.11 65 Thalassarche chrysostoma Grey headed albatross Campbell Is. th 7500 31500 3.25 10 12 1 10.2 1 0.11 64 Thalassarche eremita Chatham albatross Chatham Is. th 3700 15300 3.00 70 9 1 24.1 1 0.16 65 Thalassarche impavida Campbell albatross Campbell Is. th 22000 90999 3.00 20 12 1 54.6 1 0.11 65 Thalassarche salvini Salvin's albatross Bounty Is. th 30752 129177 4.00 10 12 1 51.7 1 0.11 60 Thalassarche steadi White-capped albatross Auckland Is. th 78120 317475 4.00 10 12 1 127.0 1 0.11 60 Thelassarche melanophrys Black-browed albatross Antipodes/Campbell/Snares Is. non-th 140 588 3.00 2 12 1 0.0 1 0.11 65

Ecosystem Modelling of the Chatham Rise 51

References Bradford-Grieve, J.M., Probert, P.K., Nodder, S.D., Thompson, D., Hall, J., Hanchet, S., Boyd, P., Zeldis, J., Baker, A.N., Best, H.A., Broekhuizen, N., Childerhouse, S., Clark, M., Hadfield, M., Safi, K. and Wilkinson, I. (2003). Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology 289: 223-262.

Brando, V.E.; Ceccarelli, R.; Libralato, S.; Ravagnan, G. (2004). Assessment of environmental management effects in a shallow water basin using mass-balance models. Ecological Modelling 172: 213-232.

Carrier, D.R.; J. Auriemma (1992). A developmental constraint on the fledging time of birds. Biological Journal of the Linnean Society, 47(1): 61-77.

Crawford, R.J.M., Ryan, P.G., Williams, A.J., (1991). Seabird consumption and production in the Benguela and western Agulhas ecosystems. S. Afr. J. Mar. Sci. 11, 357-375.

Croxall, J.P. (1987). Seabirds: feeding ecology and role in marine ecosystems. Cambridge University Press, pp408. Lasiewski, R.C., and Dawson, W.R., 1967. A re-examination of the relation between standard metabolic rate and body weight in birds. Condor, 69, 13-23.

Heather, B. and Robertson, H., (1996). The Field Guide to the Birds of New Zealand. Penguin Books, New York. pp 432.

Jackson, S. (1986). Assimilation efficiencies of white-chinned petrels (Procellaria aequinoctialis) fed different prey. Comparative Biochemistry and Physiology A 85A: 301-303.

James, G.D. and Stahl, J.-C. (2000). Diet of southern Buller's albatross (Diomedea bulleri bulleri) and the importance of fishery discards during chick rearing. New Zealand Journal of Marine and Freshwater Research 34: 435–454.

Lasiewski, R.C.; Dawson, W.R. (1967). A re-examination of the relation between standard metabolic rate and body weight in birds. Condor 69, 13-23.

Mund, M.J.; Miller, G.D. (1995). Diet of south polar skua Catharacta maccormicki at Cape Bird, Ross Island, Antarctica. Polar Biology 15: 453–455.

Nagy, K.A. (1987). Field metabolic rate and food requirement scaling in mammals and birds. Ecological Monographs 57: 111-128.

Pinkerton, M.H.; C.J. Lundquist; C.A.J. Duffy; D.J. Freeman (2008). Trophic modelling of a New Zealand rocky reef ecosystem using simultaneous adjustment of diet, biomass and energetic parameters. Journal of Experimental Marine Biology and Ecology 367 (2008) 189–203.

Pinkerton, M.H.; J.M. Bradford-Grieve; S.M. Hanchet (2010). A balanced model of the food web of the Ross Sea, Antarctica. CCAMLR Science, 17: 1–31.

52 Ecosystem Modelling of the Chatham Rise

Prinzinger, R. (1993). Life span in birds and the ageing theory of absolute metabolic scope. Comparative Biochemistry and Physiology Part A: Physiology, 105(4): 609-615.

Schneider, D.; Hunt, G.L., (1982). Carbon flux to seabirds in waters with differenet mixing regimes in the southeastern Bering Sea. Marine Biology, 67, 337-344.

Speakman, J.R. (2005). Body size, energy metabolism and lifespan. J. Exp. Biol. 208: 1717-1730.

Tasker, M.L., C.J.K. Camphuysen, J. Cooper, S. Garthe, W.A. Montevecchi and S.J.M. Blaber (2000). The impacts of fishing on marine birds. ICES Journal of Marine Science 57, 531-547.

Taylor, G.A. (2000a). Action Plan for Seabird Conservation in New Zealand. Part A: Threatened Seabirds. Threatened Species Occasional Publication 16. 234 p.

Taylor, G.A. (2000b). Action Plan for Seabird Conservation in New Zealand. Part B: Non-Threatened Seabirds. Threatened Species Occasional Publication 17. 201p.

Vinogradov, A.P. (1953). The elementary chemical composition of marine organisms. Memoir of the Sears Foundation for Marine Research, Yale University, New Haven II, 647 pp.

Weathers, W.W. (1992). Scaling nestling energy requirement. Ibis 134: 124–153.

Westmoreland, D.; L.B. Best; D.E. Blockstein (1986). Multiple brooding as a reproductive strategy: time-conserving adaptation in mourning doves. Auk 103: 196–203.

Wolff, M., (1994). A trophic study for Tongoy Bay – a system exposed to suspended scallop culture (Northern Chile). J. Exp. Mar. Biol. Ecol. 182, 149-168.

Ecosystem Modelling of the Chatham Rise 53

Appendix B Cetaceans

Introduction There are a number of species of toothed whales and dolphins that are likely to have the Chatham Rise region in their living range (e.g. Gaskin, 1982; Baker, 1990) – see Table B1. These include Arnoux’s beaked whale ( Berardius arnuxii ), southern bottlenose whale (Hyperoodon planifrons ), hourglass dolphin (Lagenorhynchus cruciger ), Andrew’s beaked whale (Mesoplodon bowdoini ), straptoothed beaked whale (Mesoplodon layardii ), spectacled porpoise ( Phocoena dioptrica ), goosebeak whale ( Ziphius cavirostris ), southern rightwhale dolphin ( Lissodelphus peronii ), bottlenose dolphin ( Tursiops truncatus), harbour porpoise (Phocoena phocoena ). The sperm whale ( Physeter macrocephalus ), orca ( Orcinus orca ), and baleen whales including Eubalaena australis (right whale), Balaenoptera acutorostrata (minke whale), B. musculus (blue whale), B. physalus (fin whale), B. borealis (sei whale), and Megaptera novaeangliae (humpback whale).

Species of cetaceans occurring in the study area are considered in two trophic groups – (1) baleen whales (Mysticeti) and (2) toothed whales and dolphins (Odontoceti) which include most beaked whales. Parameters for the trophic model were estimated separately for individual species and then combined according to their relative biomass in the study area. Information on cetaceans in the Chatham Rise area by species (or species group) is given below.

Biomass Little is known of the migration patterns, global abundances, or numbers of the species of cetaceans that occur in the study area. We have not been able to locate any systematic sighting data from the study area that would give estimates of numbers over the Chatham Rise. Instead, we use incidental sightings (data provided by Department of Conservation; Martin Cawthorn database) and expert knowledge (Dr Leigh Torres, NIWA, Wellington) to identify species likely to be present in the study area. Where no better local estimates were available, we estimated numbers (and hence biomass) using modelled data on the habitat preference of species of cetaceans through the Southern Ocean (south of 40°S) from Kaschner (2004).

Research at the University of British Columbia (Kaschner 2004) has developed a new, quasi- objective approach to map global geographic ranges of marine mammals using the Relative Environmental Suitability (RES) for 115 marine mammal species. This habitat suitability model is a rule-based environmental envelope model that uses quantitative data and alternative, non-quantitative and more readily available information about species habitat preferences (such as expert knowledge). As a first step, Kaschner (2004) assigned each species to broad-scale ecological niche categories with respect to depth, sea surface temperature and ice edge association based on synopses of published qualitative and quantitative habitat preference information. Within a global grid with 0.5° latitude by 0.5° longitude cell dimensions, an index of the relative environmental suitability (RES) of each cell for a given species was calculated by relating quantified habitat preferences to locally averaged environmental conditions in a GIS modelling framework. These were interpolated to a 0.125° x 0.125° grid using bilinear interpolation. RES predictions closely matched published distributions for most species, suggesting that this rule-based approach for

54 Ecosystem Modelling of the Chatham Rise

delineating range extents represents a useful, less subjective alternative to existing sketched distributional outlines. Kaschner (2004) validated RES model outputs for four species (northern fur seals, harbour porpoises, sperm whales and Antarctic minke whales) from a broad taxonomic and geographic range using “at-sea” sightings from dedicated surveys. The preliminary validation provided support that RES predictions capture patterns of species occurrence sufficiently enough to be used as the basis for large-scale investigations of marine mammal occurrence. RES values represent relative environmental probabilities, ranging between 0 and 1 and areas of low environmental suitability are probably more representative of potential habitat rather than representing the realized niche. Based on the various validation approaches, 0.2–0.4 is the approximate threshold at which observed species occurrence may be expected to increase substantially. Area-weighted RES values were calculated for the Chatham Rise study area, Pacific sector of the Southern Ocean (150°E–80°W, south of 40°S) and for the circumpolar Southern Ocean (south of 40°S). These were used to scale population estimates for the Southern Ocean and/or Pacific Ocean sector of the Southern Ocean to estimate numbers in the study area. Average adult weights of cetacean species are taken from Shirihai (2008). The parameters were combined to estimate biomass as equation B1.

NWC S  M  B =    [B1] A 100  12 

B = average annual biomass density (gC m -2) N = Number of animals in the study area (seasonal maximum) W = average weight of animal (gWW [wet-weight]) C = carbon:wet weight ratio (gC/gWW) A = area of study region (m 2) S = proportion of foraging area covered by the study region (%) M = months spent in the study area per year

Baleen whales (Mysticeti) In general, baleen whale populations are assumed to migrate through the New Zealand region and may enter the Chatham Rise study area. All species of baleen whale are thought to breed in tropical, subtropical or warm temperature waters in winter and feed in polar or cold temperate waters in summer, with spring and autumn migrations between the two regions (Brown & Lockyer, 1984).

Right whale Based on historical whaling records and recent sightings, southern right whales ( Eubalaena australis ) generally inhabit waters between 20 and 60° latitude (Townsend 1935; Brown 1986; Ohsumi & Kasamatsu 1986; Scarff 1986; Hamner et al. 1988). Southern right whales were once widely distributed throughout the waters of New Zealand but were the target of pelagic and shore whaling from the beginning of the nineteenth century and, as in all other areas where right whales were encountered, hunting was so intense that this species had virtually disappeared from these regions by the twentieth century (Dawbin 1986).

Southern right whales still occur in the New Zealand region (Figure B1). Many features are still unknown about right whale populations in New Zealand waters. Right whales calve in

Ecosystem Modelling of the Chatham Rise 55

coastal waters in winter months and tend to migrate offshore to feeding grounds during summer months. The IWC (2001) recognise seven winter calving grounds in the South Pacific/Indian Ocean basin. These are (1) Chile/Peru, (2) Crozet I., (3) Central Indian Ocean (around St Paul I.), (4) New Zealand mainland/Kermadec, (5) New Zealand subantarctic (near Auckland Islands), (6) Southeast Australia, and (7) Southwest Australia. Of these, only the Southwest Australia and the New Zealand subantarctic calving grounds are showing clear signs of recovery. Historically, right whale cows calved in bays along the east coast of mainland New Zealand and around the sub-Antarctic islands during the austral winter, moving offshore during the summer months (McNab 1913; Dawbin 1986). In winter, right whales migrate north to New Zealand waters and large concentrations occasionally visit the southern coasts of South Island. Bay areas along Foveaux Strait from Fiordland region to northern Otago are important breeding habitats for right whales, especially Preservation Inlet, Te Waewae Bay and Otago coast.

Sightings from mainland New Zealand imply a very small, remnant population of southern right whales inhabiting waters off both North and South Island, containing ca. 11 reproductive females (Patenaude, 2003) and perhaps of the order of 30 whales. The most recent population estimate is 10,000 (International Whaling Commission workshop) based on adult female data from three surveys in Argentina, South Africa and Australia, during the 1990s. On the basis of RES mapping (Kaschner 2008), this would imply an average number in the Chatham Rise study area of 55 whales. The distribution of right whales in summer is likely linked to the distribution of their principal prey species (copepods and euphausiids): Best & Schell (1996); Woodley & Gaskin (1996); Tormosov et al. (1998). The Chatham Rise area is particularly productive in terms of these prey species. For the Chatham Rise model, we assume half the population of 30 right whales are in the study area for 6 months of the year.

Southern right whale adults reach up to 17 m in length (females grow larger than males) with maximum weights of up to 50 t, though most are 20-30 t (Shirihai, 2007). Here, we use 25 t as the mean weight in the population. Newborn animals are 4-5 m long (SeaMap 2005), and may weigh ca. 3 t. Lifespan may be 70 years (Kenney 2002).

Southern right whales use surface and subsurface skim feeding, with main prey being copepods and krill, apparently sometimes feeding near the bottom in shallow habitats (SeaMap 2005; Cummings 1985). We assume a diet of southern right whales in the study region of 50% crustacean macrozooplankton; 30% mesozooplankton; 20% gelatinous zooplankton.

56 Ecosystem Modelling of the Chatham Rise

Figure B1: Distribution of sightings of southern right whales in New Zealand waters.

Minke whale The minke whale is one of the best studied baleen whales in the world but has had an unclear taxonomy (Stewart & Leatherwood 1985). Here, we use Rice (1998) as representing the current state of knowledge in the field of cetacean taxonomy, which is that two separate species of minke whale may be found in the region: dwarf minke whale (Balaenoptera acuturostrata un-named subspecies), and Antarctic minke whale (Balaenoptera bonarensis ). In this work, where we refer to “minke whales” we are referring to the combination of the two species. We are not aware of information that gives reliable information on the relative proportions of these species in the region.

Minke whales in the southern hemisphere are pelagic and circumpolar. They are found up to the Antarctic pack ice in summer, moving north by thousands of kilometres to warmer temperate and equatorial waters of the South Atlantic, Indian, and South Pacific Oceans in winter (Kasamatsu et al. 1995). Minke whales were observed on 5 occasions from 1983– 2003 over the Chatham Rise, including a group of 5 animals (Figure B2).

The Southern Ocean population of minke whales has been estimated as ca. 380,000 (SeaMap 2005) or 580,000 animals (International Whaling Commission 1984; Northridge 1984). Taking the Southern Ocean population to be the average of these estimates, and using the RES mapping of Kaschner (2008) we may estimate a population of minke whales south of 60°S between 150°W–150°E of the order of 112,000 whales.

Ecosystem Modelling of the Chatham Rise 57

To check, the method using RES and this Southern Ocean population would estimate a number in the Ross Sea (south of 69°S, 160°E–160°W) of 29,000 minke whales. This is of about twice the value of 14,300±18,100 used in Pinkerton et al. (2010) based on at-sea sighting data from (Ainley 1985). If the Ross Sea sector population of minke whales (14,3000) moves north through the New Zealand region on the way to tropical waters, we use RES mapping of Kaschner (2008) to estimate 1720 minke whales in the study region at some time in the year. We assume this number of minke whales is in the Chatham Rise region for a total of 1 month per year.

Typical maximum lengths of Antarctic minke whales are given as 9.8 m (male) and 10.7 m (female) by Trites & Pauly (1998). Based on Konishi et al. (2008) we estimate maximum weights of Antarctic minke whales of 9.7 t (male) and 11.8 t (female). Average weights within the population were estimated to be 6.1 t and 7.0 t for male and female whales respectively (Trites & Pauly 1998). Dwarf minke whales are smaller than the Antarctic minke whale, approximately 7.8 m long (female) and 7.1 m (male) (Arnold et al. 1987; Best 1985). These values, and the length-weight relationship of Lockyer (1976), suggest maximum weights for dwarf minke whales in the Antarctic of 2.7 t (male) and 3.5 t (female). The mean weight of individual minke whales in the region is calculated assuming that there are equal numbers of Antarctic minke whales and dwarf minke whales, and equal numbers of males and females. The mean individual weight of minke whales in the Chatham Rise is hence estimated to be 4.8 t. The Antarctic minke whale is a long-lived species - those sampled by Konishi et al. (2008) were aged up to 63 (males) and 59 (females) years.

Minke whales use two forms of feeding: lunge feeding and bird-association feeding. In the Southern Ocean, minke whale diet is dominated by pelagic crustaceans, especially krill (Knox 2007). Saino & Guglielmo (2000) encountered a large proportion of minke whales where acoustic surveys indicated very large swarms of krill. It seems that minke whales are flexible in their choice of food and adjust their diet according to food availability with few strong preferences (Skaug et al. 1997). Minke whales are certainly able to feed on small pelagic and demersal fish, such as sand eel, mackerel, and anchovy (e.g., Olsen & Holst 2001; Tamura 2003). A single minke whale feeding twice daily is reported as consuming an estimated 21.5 and 33.8 t (male and female respectively) of food over three to four months in the Antarctic (Armstrong & Siegfried 1991), consistent with values based on our Q/B value which gives 24.5 t. Ichii & Kato (1991) estimate higher values of 33.6–39.6 t. Proportions in the diet are estimated as 25% small pelagic fishes; 70% macrozooplankton and 5% mesozooplankton.

58 Ecosystem Modelling of the Chatham Rise

Figure B2: Distribution of sightings of minke whales in New Zealand waters.

Blue whale Populations of the Antarctic blue whale ( Balaenoptera musculus intermedia ) migrate seasonally, moving poleward in spring to exploit the high productivity of the cold waters and travelling into the subtropics in autumn to reduce energy expenditures, avoid ice entrapment, and reproduce in warmer waters. Individuals do not stay in one area for very long, travelling solitarily or in pairs, and are found in both coastal and pelagic environments (Branch et al. 2007 and references therein). Blue whale numbers in the New Zealand region are not well known, but sightings (Figure B3) indicate that some blue whales pass through the region (see also Shirihai 2002); there were two sightings in the Chatham Rise region in summer 1984 and autumn 1998.

The Southern Ocean blue whale population is estimated at 400–1400 individuals (IUCN 2005). Three complete circumpolar surveys completed during 1978–79 to 2003–04 indicated a population rate of increase of 8.2% per year, although the total numbers are still under 1% of their pre-exploitation abundance (Branch 2008). Based on Kaschner (2008) estimates south of 60°S, and taking a Southern Ocean population of 1700 (average of 400 and 1400, with 8.2% per year increase since 2005), we estimate 372 animals south of 60°S between 150°W–150°E. Assuming these animals move north according to RES estimates from Kaschner (2008) north of 60°S, we estimate 6 animals transit the Chatham Rise region.

Zenkovich (1970) gives blue whales spending 120 d y-1 in Antarctic (c. 4 months), over the summer period. Seasonal and spatial variations of blue whale calls were analysed from recordings collected by acoustic recording devices at 4 circumpolar sites during 2003 and 2004, including a site south of 70° in the Ross Sea from 2 March to 16 June 2004 (Širovi ć et al. 2009). The results found that the highest number of blue whale calls was detected at the Ross Sea site during March, but there were no calls there after April. Here we assume that blue whales are in the Chatham Rise area for a total of 1 month per year.

Ecosystem Modelling of the Chatham Rise 59

The Antarctic blue whale ( Balaenoptera musculus intermedia ) is larger than its northern relations, and generally measures up to 29 m, although a specimen over 33 m was once taken by whalers. Adults can weigh up to 190 tons, but most adults are 80–150 tons. Lockyer (1981a) gives 102 t (female) and 117 t (male) as average maximum weights of blue whales. Mackintosh (1965) gives 83.8 t as the average weight of a blue whale, and here we use 103 t (Trites & Pauly 1998). Blue whales are long lived, with a lifespan (90 th percentile) estimated at 100 years (Trites & Pauly 1998).

Reproductive activity takes place during winter, in the warmer waters of their range i.e. outside the study region. We assume blue whale diet in the Chatham Rise is: 90% macrozooplankton; 5% mesozooplankton and 5% small pelagic fishes.

Figure B3: Distribution of sightings of blue whales in New Zealand waters.

Sei whale The sei whale ( Balaenoptera borealis ) lives mainly in the open ocean and not often seen near the coast. They occur from the tropics to polar zones in both hemispheres, but prefer warmer waters to fin and blue whales and are consequently more restricted to mid-latitude temperate zones (Tomilin 1957; Mackintosh 1965). They do undergo seasonal migrations, although they apparently are not as extensive as those of some other large whales. A few sightings of sei whales have been made in the study area (Figure B4) indicating that some sei whales are likely to pass through the Chatham Rise area each year. Current global abundance of the sei whale is considered to be about 39,000–80,000 (Young 2000; SeaMap 2005). The population of sei whales in the southern hemisphere has been estimated at between 15,000 and 30,000 (International Whaling Commission 1980). Tamura (2003) gives a number of 10,860 for the southern hemisphere including the Indian Ocean.

60 Ecosystem Modelling of the Chatham Rise

Based on Kaschner (2008) estimates of sei whale distribution, and taking a Southern Ocean population of 18,600 (average of 15,000, 30,000, 10,860), we estimate 4500 animals south of 60°S between 150°W–150°E. Assuming these animals move north according to RES estimates from Kaschner (2008) north of 60°S, we estimate 74 animals may transit the Chatham Rise region. Applying Kaschner (2008) estimates for distributions south of 40°S, we would estimate 44 sei whales in the Chatham Rise area over a year. We use an average of these (59 whales). Zenkovich (1970) estimated that sei whales are present in the Southern Ocean for only 100 days per year. Because of their preference for open-ocean temperate waters, we assume that sei whales only occur in the Chatham Rise region for 1 month in total per year.

Adult sei whales can be up to 18 m in length, although 15 m is a more typical length for adults. Large adults may weigh 30 t (SeaMap 2005). Mackintosh (1965) suggests 22.2 t as an average weight of sei whales. Lockyer (1981a) gives 18 t (female) and 19.5 t (male) as average maximum weights. Here, we use a mean weight for the population of 16.8 t (Trites & Pauly 1998). 90 th percentile of longevity is reported to be 69 years (Trites & Pauly 1998).

Sei whales skim copepods and other mesozooplankton, rather than lunging and gulping, like other rorquals. The diet, according to Kawamura (1974), includes not only euphausiids but also other swarming crustacea such as the amphipod Parathemisto (Northridge 1984). We assume their diet is: 75% macrozooplankton; 20% mesozooplankton and 5% small pelagic fishes.

Figure B4: Distribution of sightings of sei whales in New Zealand waters.

Ecosystem Modelling of the Chatham Rise 61

Humpback whale The humpback whale ( Megaptera novaengliae ) is found in all the major ocean basins and migrates long distances; in the summer, humpbacks migrate poleward to exploit the high productivity of the cold waters and in winter travel to warm tropical waters (especially around Tonga: Shirihai 2002). Numbers of humpback whales in the study area are not known. There were 397 reported sightings of humpback whales in the New Zealand region between 1981 and 2007 from the DoC incidental sightings database and the Cawthorn sightings database (L. Torres, NIWA, pers. com.). Most incidental sightings of Humpback whales in the New Zealand region are along the north-east coast of the North Island with another concentration in the Cook Strait region (Figure B5). Four sightings of 5 individuals were made over the Chatham Rise in autumn/summer. We note that the same whales may be sighted more than once in any year and that lack of sightings may reflect lack of observation rather than absence.

Globally, there may be about 22,000–40,000 humpback whales (Young 2000; SeaMap 2005) but more recent work suggests that this may be an underestimate. In the Southern Ocean, the population of humpback whales is thought to number a few thousand (Northridge 1984). Laws (1977) gives figures of 100,000 and 3000 for total southern stock sizes before and after exploitation. Tamura (2003) gives a population size for ocean south of 30°S as 10,000 (based on International Whaling Commission 2000). Austral summer estimates of abundance in the Southern Ocean from three circumpolar surveys completed in the period 1978–79 to 2003–04 indicated that all breeding stocks are increasing and the rate of increase is >5% (Branch 2006). We assume a Southern Ocean population of 15,000 (Pinkerton et al., 2010). Based on this Southern Ocean population and RES habitat modelling (Kaschner 2004), we estimate 45 humpback whales in the Chatham Rise study region. Zenkovich (1970) estimated that Southern Ocean populations of humpback whales spent 120 d y -1 in the Antarctic region so presumably humpback whales in the New Zealand region are animals migrating from/to the tropical calving and mating areas to/from the summer feeding grounds in the vicinity of the Ross Sea. We assume that this migration is for 1 month (total) per year.

Humpback whales measure 11–17 m as adults and attain a weight of ca. 35 t (SeaMap 2005). Mackintosh (1965) gives 33.2 t as a typical adult weight. Here, we use 30 t as the average weight within a population of humpback whales (Trites & Pauly 1998). Longevity is reported as 75 y (Trites & Pauly 1998).

Chittleborough (1965) states that Euphausia superba is the main food item, but that the krill Thysanoessa macrura is also eaten (Northridge 1984). Humpback whales are generalists, eating krill, copepods, fish, and cephalopods. Humpback whales exhibit a wide range of feeding habits intended to concentrate prey, which may be employed individually or in groups, including lunging, bubble-netting and lob-tail feeding (SeaMap 2005). Bottom feeding has also been documented. We assume a diet of humpback whales in the study region of: 50% crustacean macrozooplankton; 30% mesozooplankton; 20% gelatinous zooplankton.

62 Ecosystem Modelling of the Chatham Rise

Figure B5: Distribution of sightings of humpback whales in New Zealand waters.

Pygmy right whale The pygmy right whale (Caperea marginata ) is rarely encountered and consequently little studied. Population sizes are unknown. It is possible that pygmy right whales occur in the study area as it is thought to have a circumpolar distribution through the Southern Ocean. The pygmy right whale is by far the smallest of the baleen whales, with adult maximum length of about 6 m. Adult pygmy right whales weigh 2.8–3.4 t (Nowak, 1999). In 2001 a group of 14 were seen at 46°S in the South Pacific about 450 km southeast of New Zealand. We do not include this species in the model because of no confirmed sightings in the area.

Ecosystem Modelling of the Chatham Rise 63

Toothed whales & dolphins (Odontoceti)

Sperm whale Sperm whales ( Physeter macrocephalus ) are migratory and are distributed from the tropics to the pack ice edges in both hemispheres, although generally only large males venture to the extreme southern portions of the range (e.g., Gaskin 1973). Sperm whales are deep divers, apparently capable of reaching depths of >3200 m, and commonly diving to more than 400 m. Sperm whales tend to inhabit oceanic waters, coming close to shore where submarine canyons or other physical features bring deep water near the coast. Sperm whales are relatively common in New Zealand waters, with over 20 sightings of sperm whales have been made in the Chatham Rise area (Figure B6). The majority of sightings were made in summer and often near the 1000 m isobath on steep slopes, where their prey (cephalopods) tend to be most common (Halliday et al. 2011; Shirihai 2002). Although the subtropical convergence is often taken to mark the southern limit of females and young males, with only the larger males penetrating further south (Knox 2007; Lockyer & Brown 1981), sighting data over the Chatham Rise south of 40°S included mother/calf groups. The Chatham Rise is hence probably a foraging ground for some sperm whales.

The number of sperm whales in the New Zealand region is not well known. The species was subject to high catches through the 20 th century. Global and Southern Ocean population in the mid-1980s was estimated at 982,200 and 410,700 respectively (Klinowska 1991). In 2000, the global population was estimated to be 360,400 (Baker & Clapham 2004), but there are estimated to be only 28,100 individuals south of 50°S (Kasamatsu & Joyce 1995), and 12,000 south of 60°S (Whitehead 2002; International Whaling Commission 2001). Based on Kaschner (2008) RES estimates of sperm whale distribution, and taking a Southern Ocean population (south of 40°S) of 151,000 (Baker & Clapham 2004 adjusted by Klinowska 1991), gives an estimate of the number of sperm whales on the Chatham Rise of 307 whales. Based on Kaschner (2008) RES and a population south of 60°S of 12,000 gives 114 sperm whales on the Chatham Rise. Based on Kaschner (2008) RES and a population south of 50°S of 28,100 gives 100 sperm whales on the Chatham Rise. We use an average of these as our best estimate i.e. 173 whales. Sperm whales migrate seasonally, and we assume that these sperm whales are present in the Chatham Rise region for only 3 months of the year.

Newborn sperm whales are 3.5–4.5 m long. Adult females are up to 12 m and adult males are up to 18 m in length. Weights of up to 57 t have been recorded (SeaMap 2005). Other work gives 33 t as an approximate average value (Gaskin 1982; Bradford-Grieve et al. 2003). Here, we use the value for mean weight for male sperm whales of 27 t (Lockyer 1981b). Longevity is typically 60–70 y (Whitehead & Weilgart 2000)

Prey is taken by seizing individual items. A wide variety of prey items have been found in the stomachs of sperm whales from around the world, but cephalopods (squid and octopuses), and fish (especially demersal fish) are considered to be the major prey items (Nemoto et al. 1985; Jefferson et al. 1993; Perry et al. 1999; Whitehead 2003). Some data suggests that their diet is almost exclusively cephalopods (Laws 1977; Northridge 1984). Sperm whales in the Southern Ocean and Pacific subantarctic are reported as feeding primarily on squid and secondarily on fish (Clarke 1980; Knox 2007; Evans & Hindell 2004). Knox (2007) gives the ratio of squid to fish in their diet as 9:1. Here we use a diet of 90% squid, 5% pelagic fishes and 5% demersal fishes.

64 Ecosystem Modelling of the Chatham Rise

Figure B6: Distribution of sightings of sperm whales in New Zealand waters.

Pilot whale Both long-finned pinot whales ( Globicephala melas ) and short-finned pilot whales ( G. macrorhynchus ) occur in New Zealand waters. Numbers, movement rates and distribution patterns of pilot whales in the study region are not known, but pilot whales are sighted in the region (Figure B7). Although the two species of pilot whale differ in flipper length, skull shape and number of teeth, they can be difficult to distinguish at sea so sighting information at sea is generally unreliable and so we take the species together. Given the habitat preferences for the species (see below), it is likely that most pilot whales in the Chatham Rise area are long- finned pilot whales. For this study, we take the average adult weights of pilot whales to be 1800 kg (mean of data from Jefferson et al. 2008). Numbers are estimated from sightings in the study area (Halliday et al. 2011) of 331 individuals being present for the equivalent of 6 months a year. Longevity is taken as about 45 years in males and 60 years in females for both species (mean 53 y). There are probably considerable differences between the diet of long- and short-finned pilot whales at the species level, but both feed predominantly on squid. In the trophic model, the diet of pilot whales is set to be 90% squid, 10% medium-large sized demersal fish.

Ecosystem Modelling of the Chatham Rise 65

Figure B7: Distribution of sightings of pilot whales in New Zealand waters.

Long-finned pilot whale This summary of the biology and feeding of the long-finned pilot whale is largely taken from Culik (2010a). Two subspecies of long-finned pilot whales are recognized in some classifications (Rice 1998): (1) northern hemisphere subspecies, G. m. melas , which ranges in the North Atlantic from Greenland to the western Mediterranean; (2) southern hemisphere subspecies, G. m. edwardii , which is circumglobal in the Southern Hemisphere, ranging north to Brazil, South Africa, Iles Crozet, Heard Island, the southern coast of Australia, and north of New Zealand, encompassing the study area. Southward it extends at least as far as the Antarctic Convergence 47°S to 62°S and has been recorded near Scott Island (67°S, 179°W) and in the central Pacific sector at 68°S, 120°W (Rice 1998). There is little information on stocks within the species, and there is no information on global trends in abundance (Taylor et al. 2008). Population estimates for the southern hemisphere subspecies is in the order of 200,000 long-finned pilot whales (Bernard & Reilly 1999). The typical temperature range for the species is 0-25°C (Martin 1994) and is mainly found in offshore waters (Reyes 1991). Calving and breeding can apparently occur at any time of the year, but peaks occur in summer in both hemispheres (Jefferson et al. 1993). Strandings of long-finned pilot whales in northern New Zealand occur year-round though more commonly in spring and summer (O’Callaghan et al. 2001). Adult long-finned pilot whales reach a body length of approximately 6.5 m, males being ca. 1 m larger than adult females (Bloch et al. 1993; Olson, 2009). Body mass reaches up to 1300 kg in females and up to 2300 kg in males (Jefferson et al. 2008). These values are lower than given by Shirihai (2008) of 2600 kg. For this study, we take the average adult weights of long-finned pilot whales to be 1800 kg (mean of data from Jefferson et al. 2008).

66 Ecosystem Modelling of the Chatham Rise

The diet of long-finned pilot whales in the study area is not known. Elsewhere, pilot whales are primarily squid eaters, but will also take small medium-sized fish (Desportes & Mouritsen 1993; Jefferson et al. 1993). They feed mostly at night, when dives may last for 18 minutes or more and reach 828 m depth (Carwardine 1995; Heide-Jørgensen et al. 2002). In the northern hemisphere, the main prey was found to be squid (Illex illecebrosus , Loligo pealei , Todarodes sagittatus , species of the genus Gonatus ), although cod ( Gadus morhua ), Greenland turbot ( Rheinhardtius hippoglossoides ), Atlantic mackerel ( Scomber scombrus ), turbot ( Scomber scombris ), herring ( Clupea harengus ), hake ( Merluccios bilinearis ; Urophysis spec.) and dogfish ( Squalus acanthias ) were also eaten (Abend & Smith 1997; Olson 2009; Mintzer et al. 2008). In the southern hemisphere, although squids are the predominant prey around the Faroe Islands, some fish, such as Argentina silus and Micromesistius poutassou , are taken too. The whales in this region do not appear to select cod, herring or mackerel, although they are periodically abundant (Reyes 1991; Desportes & Mouritsen 1993; Bernard & Reilly 1999). Off the South Island of New Zealand, long-finned pilot whales feed exclusively on cephalopods, mainly arrow squid, Nototodarus spp., and common octopus, Pinnoctopus cordiformis (Beatson & O'Shea 2009).

Short-finned pilot whale This summary of the biology and feeding of the short-finned pilot whale ( Globicephala macrorhynchus ) is based on Culik (2010b). Short-finned pilot whales are found in deep offshore areas and usually do not range north of 50°N or south of 40°S (Jefferson et al. 1993), so that the Chatham Rise is towards the south limit of the range of this species. The number of short-finned pilot whales in the western Pacific is poorly known but may be of the order of 100,000 individuals (Culik 2010b). The species prefers deep water and occurs mainly at the edge of the continental shelf and over deep submarine canyons (Carwardine, 1995). Davis et al. (1998) found that G. macrorhynchus in the Gulf of Mexico preferred water depths between 600 and 1,000 m. Although short-finned pilot whales are highly susceptible to stranding events (Mazzuca et al. 1999), short-finned pilot whales do not strand in New Zealand. The preference for deep water habitat is supported by diet studies. Mintzer et al. (2008) examined the stomach contents of short-finned pilot whales from the North Carolina coast and found they predominantly consume squid ( Brachioteuthis riisei , Taonius pavo , Histioteuthis reversa ), and also fish (Scopelogadus beanii ). The results indicated that the whales fed primarily off the continental shelf prior to stranding. Stomach content composition differed from those of short-finned pilot whales from the Pacific coast in which neritic species dominate the diet. Adult females of short-finned pilot whales reach a body length of approximately 5.5 m and males 7.2 m, with a body weight of up to 3200 kg (Jefferson et al. 2008).

Common dolphin Common dolphins of the genus Delphinus are common in temperate waters to about 50°S. Common dolphins are commonly sighted in New Zealand coastal waters (Figure B8), especially off the east coast of the North Island (Webb 1973). Sightings are often assumed to be the short-beaked common dolphin ( D. delphis ). However, extensive morphological variation (Stockin & Visser 2005) and the absence of any molecular studies prevent the taxonomic clarification of Delphinus in New Zealand waters, and more recently, New Zealand common dolphin have been referred to as Delphinus sp. (Stockin et al. 2007; Stockin et al.

Ecosystem Modelling of the Chatham Rise 67

2008a, b). The conservation status of common dolphin is considered of “least concern” by the IUCN, owing to the global abundance of this species (IUCN 2007).

In New Zealand waters, common dolphins are abundant but no population estimate exists (Meynier et al. 2008). Between February 2002 and January 2005, Stockin et al. (2008b) recorded 719 independent encounters with common dolphins in the Hauraki Gulf, involving 1 to >300 animals, which sets a lower limit on the New Zealand population. Calves were observed throughout the year but were most prevalent in the austral summer months of December and January. There have been only a few sightings (4) of common dolphins in offshore waters in the Chatham Rise study region and all these occurred in autumn. However, the general ecology of common dolphins is typically warmer temperate or tropical waters and principally offshore (Shirihai 2002) so the few sightings may be mainly due to low observation effort. For the eastern tropical Pacific, Gerrodette et al. (2008) estimated a population of common dolphins of 3.1 million in 2006, very similar to that estimated by Evans (1994) for the same region. Simply based on approximate area of the habitat shown by Hammond et al. (2008), the New Zealand-Australia population of Delphinus sp. may be 10% of this. The proportion of the habitat south of 40°S in the New Zealand region is about 20%. Using RES (Kaschner 2004) to estimate numbers in the Chatham Rise region, we obtain an estimate of 2500 animals in the Chatham Rise region. In the model, we assume this number of common dolphins is found in the study area only in the autumn (3 months per year).

Common dolphins can reach lengths of 2.3–2.6 m and weigh up to 135 kg, though 70–110 kg is typical. We take the average weight of common dolphin in the study region to be 90 kg. Average lifespan may be 25 years.

Stomach contents of 42 stranded and 11 by-caught common dolphin from the North Island of New Zealand between 1997 and 2006 was analysed by Meynier et al. (2008). Their diet comprised a diverse range of fish and cephalopod species, with prevalent prey of arrow squid (Nototodarus spp.), pelagic fishes (jack mackerel Trachurus spp.; anchovy Engraulis australis ; redbait Emmelichthys nitidus; yellow-eyed mullet, Aldrichetta forsteri ) and demersal fish (grey mullet, Mugil cephalus ; scarpee Helicolenus percoides ; dwarf cod Austrophycis marginata ; cardinal fish, Epigonus sp.) (Meynier et al. 2008). Here, we take diet of common dolphins to be 23% squid, 77% small pelagic fishes.

68 Ecosystem Modelling of the Chatham Rise

Figure B8: Upper: Distribution of sightings of common dolphins in New Zealand waters (DoC; Cawthorn). Lower: Distribution of Delphinus delphis : worldwide (Hammond et al. 2008; IUCN).

Ecosystem Modelling of the Chatham Rise 69

Orca/Killer whale Orca or killer whales ( Orcinus orca ) are probably the most cosmopolitan of all cetaceans, being found from ice edges to the equator, in both hemispheres, and most usually being found to feed within 800 km from the coast (Klinowska, 1991). Orca have generally been considered to constitute a single species throughout the world (Rice 1998) even though since the 1970s several groups of researchers independently concluded that, based on differences in morphology, ecology and acoustic repertoire, there were three recognisably different forms of orca in the Antarctic (Pitman & Ensor 2003, and references therein): type A, type B and type C. Visser (2000) suggests that orca in New Zealand waters are likely to be mainly Type A.

Killer whales have been sighted in New Zealand waters in all months, though sightings in the summer are commonest perhaps due to increased observer effort. Animals move north as the temperatures cool; animals sighted in the winter months in the Hauraki Gulf and Bay of Islands were in Kaikoura and Cook Strait waters in summer months (Visser 2000). Stranded animals have been reported from the east coast of the North Island, north of Hauraki Gulf (stranding database, Visser & Fertl 2000) and multiple strandings were reported at Paraparaumu Beach (17 animals) and Chatham Islands (11 animals) (Baker 1999). All sightings reported to DoC were between 32° (North Cape) and 47° S (near Stewart Island). The New Zealand National Aquatic Biodiversity Information System (NABIS) shows orca occurring around the coast of both North and South Island, and over the Chatham Rise. The NABIS killer whale distribution map was based on the cetacean strandings database maintained by the Museum of New Zealand Te Papa Tongarewa, Wellington, and the cetacean sightings database held by DoC. The latter contained 208 records of sightings of killer whales reported mainly by DoC staff and dolphin-watching tour operators between 1990 and 2009. Combined sighting data from DoC and Martin Cawthorn is shown in Figure B9.

No robust estimates of killer whale numbers in New Zealand waters exist, but reasonable attempts at assessing population numbers have been made by Visser (2000). Baker (1999) describes killer whales as common in New Zealand waters and at least 117 individuals have been photo-identified (Visser 2000). Resighting rates were high, with 75% (n=88) of the animals seen on more than two occasions. Visser (2000) concludes that “orca in New Zealand have a population between 65 and 167 with the results from the TE [Total Enumeration] and Jolly Seber calculations suggesting that the Total Enumeration in 1997 (i.e., 115 orca) is a reliable but conservative estimate.” Visser (2000) notes that this number is well below the population size of 500 suggested by Soulé (1987) as a viable population.

Only 4 sightings of killer whales have occurred over the Chatham Rise (Figure B9) and to what extent orca in New Zealand waters forage or hunt in offshore regions like the Chatham Rise is not known. The Southern Ocean population of orca was reported as 160,000 (Hammond 1983; Northridge 1984), though this may have been an overestimate as the population around Antarctica (south of 60°S) has more recently been estimated at 70,000 animals (Klinowska, 1991). Based on RES for killer whales (Kaschner, 2004), the latter figure would imply 285 whales in the Chatham Rise area and 8900 killer whales in the New Zealand region, which seems an overestimate.

70 Ecosystem Modelling of the Chatham Rise

For the purposes of the Chatham Rise model, we assume a New Zealand population of 1000 animals (twice the minimum viable population size), and that 0.1 of the population is present in the Chatham Rise study area for 6 months per year.

Type-A male orca grow to 6.7–8.2 m (maximum 9.5 m) and females to 5.2–7.3 m (Fad, 1996). Mikhalev et al. (1981) report maximum lengths of 9.0 m and 7.7 m for male and female (respectively) Adult male type-A orca are reported as weighing up to approximately 8000 kg, and females as weighing up to 4000 kg (Baird 2000), much higher than average weights of type B and C orca. Longevity of orca in the wild is likely to be 50 y (Trites & Pauly 1998).

Visser (2000) summarises the feeding of New Zealand orca as consisting of rays, sharks, fin- fish and cetaceans (pinnipeds have not been identified as a prey source). Rays are not likely to be major prey items in the study area. Instead, the diet of orca in the Chatham Rise region is assumed to be 30% large pelagic fishes (including sharks), 30% large demersal fish and 40% small cetaceans (mainly dolphins, including common dolphin and bottlenose dolphin).

Figure B9: Distribution of sightings of orca/killer whales in New Zealand waters.

Ecosystem Modelling of the Chatham Rise 71

Dusky dolphin The dusky dolphin (Lagenorhynchus obscurus ) is a semi-pelagic species, inhabiting coastal zones and shallow shelves and slopes of the continental shelf. It is associated with landmasses of southern hemisphere continents or islands, and rarely occurs in waters deeper than 2,000 m (Cipriano & Webber 2010). It is well-known off especially the south island of New Zealand, Chile and Peru, Argentina and the Falkland Islands, and the southwest coast of southern Africa. However, it also occurs off Tasmania (and occasionally the southern-most extent of Australia proper), Tristan de Cunha and Gough Islands of the South Atlantic, and Prince Edward, Marion, Amsterdam, and St. Paul Islands of the Indian Ocean.

Dusky dolphins tend to inhabit cooler waters off most of the South Island and the lower part of North Island (Wursig et al. 2007). Two sightings of dusky dolphins were made in the Chatham Rise area (Halliday et al., 2011; Figure B10). From "mark-recapture" analysis of recognizable individuals, an estimated 12,000 dusky dolphins occur off Kaikoura, New Zealand (Markowitz 2004). Based on RES mapping (Kaschner 2008) we estimate about 550 dusky dolphins in the Chatham Rise study area.

Dusky dolphins have a maximum size is between 165 cm and 195 cm, and weight of 69–90 kg (mean 80kg, Shirihai 2008). The life span of a dusky dolphin is likely to be between 20 to 25 years.

Admiralty Bay, at the northern tip of South Island, is inhabited by dusky dolphins from late fall to early spring (6 months per year) when they feed on pilchard ( Sardinops neopilchardus ). Most individuals are males (Shelton et al. 2010). They coordinate foraging activities in groups of up to 50 individuals in order to herd prey. In general, the diet of dusky dolphins in New Zealand is dominated by pilchard ( Sardinops neopilchardus ) in Admiralty Bay and deep- scattering layer prey such as squid (Nototodarus/Todaroides spp.) and lanternfish (Symbolophorus spp., Diaphus spp., Myctophum spp., Hintonia spp.) (Würsig et al. 2007).

72 Ecosystem Modelling of the Chatham Rise

Figure B10: Distribution of sightings of dusky dolphins in New Zealand waters.

Bottlenose dolphin Bottlenose dolphins ( Tursiops truncatus ) are distributed worldwide in tropical and warm- temperate waters. There are thought to be three main areas of distribution of bottlenose dolphins in New Zealand waters (which are probably separate populations, pers. comm., Rochelle Constantine, University of Auckland): (1) northeast coast of the North Island; (2) Marlborough Sounds; and (3) Fiordland. Probably the most northern sighting of bottlenose dolphins in New Zealand waters was of a large pod near McCauley Island in the Kermadec Islands group (Dawson 1985).

Most reported sightings and strandings of bottlenose dolphins are from the northeast North Island, though strandings have been reported from Cloudy Bay and Waitarere Beach (Warneke 2001). Bottlenose dolphins around New Zealand are predominantly sighted in coastal waters and estuaries, but oceanic populations are seen off the east coast of Northland in late summer and early autumn, often associated with pilot whales (Globicephala

Ecosystem Modelling of the Chatham Rise 73

spp.) and false killer whales ( Pseudorca crassidens ) (R. Constantine pers. comm.). The northeastern population concentrated in the Bay of Islands resides year round along the east coast of Northland and in the Hauraki Gulf (Constantine et al. 2003). Photo-identification work in this area provided a closed population estimate of 446 (95% CI = 418–487) adult dolphins, with a potential home range from at least 400 km to the south (Tauranga) to about 80 km north (Doubtless Bay) (Constantine et al. 2003).

Only two sightings of bottlenose dolphins have been made in the Chatham Rise area (Figure B11) which is likely to be towards the southern limit of their range; the southernmost limit of sightings in New Zealand waters is 47°S. The size of the bottlenose dolphin groups sighted over the Chatham Rise and their distance from shore suggests that these dolphins are from an “offshore” ecotype known as Tursiops aduncus . Although the offshore ecotype is not considered “range restricted”, very little is known about their population size, distribution or ecology. For the purposes of this study, we assume a nominal 100 bottlenose dolphins (Tursiops aduncus ) in the Chatham Rise study area during the year and base other parameters on Tursiops truncates .

In general, adult bottlenose dolphins are 2.0 to 3.9 m in length, with an average weight reported as 100–200 kg, though Hutchinson & Slooten (pers. comm.) suggest that an average weight of bottlenose dolphins of ~90 kg is more appropriate. For the purposes of the model, we use an average weight of 120 kg. The life span of bottlenose dolphins is likely to be about 47 years (Trites & Pauly 1998).

Diet of bottlenose dolphins is reported as small fish, crustaceans, and squid (Wells & Scott 2002; Shirihai & Jarrett 2006). The diet of bottlenose dolphins in the study region is not known, but is likely to be similar to that of the (better studied) common dolphin. Here, we assume the diet to be: 25% squid, and 75% small or medium-sized fishes.

74 Ecosystem Modelling of the Chatham Rise

Figure B11: Distribution of sightings of bottlenose dolphins in New Zealand waters.

False killer whale False killer whales ( Pseudorca crassidens ) has a circumpolar distribution in temperate and tropical waters and tends to occupy deep water habitats (200–2000 m: Shirihai 2002). On 30 July 1986, a pod of 114 false killer whales became stranded at Town Beach, Augusta, in Flinders Bay, Western Australia. Only one sighting of a false killer whale group of two individuals during the spring of 1985 was recorded in the Chatham Rise region (Figure B12). Population numbers and ecological characteristics are not known. As the Chatham Rise is likely to be at the southernmost limit of its range, we assume a nominal 1 pod of 100 whales is present on the Chatham Rise for a nominal 1 month of the year. Males are 3.7–6.1 m and females 3.5–5.0 m long, with typical adult weight of 1.5 t (Shirihai 2002). Longevity is not known and is taken as 50 y similar to other Odonotceti of similar size. Fish is the main prey item, with squid and occasionally dolphins taken (Shirihai 2002).

Ecosystem Modelling of the Chatham Rise 75

Figure B12: Distribution of sightings of false whales in New Zealand waters.

Southern bottlenose whale Southern bottlenose whales ( Hyperoodon planifrons ) seem to be most common between 58° and 62°S in the Atlantic and eastern Indian Ocean, but low numbers have been reported in the Ross Sea (Leatherwood & Reeves 1983; Northridge 1984) south of the Chatham Rise. They are deep-water oceanic animals and tend to be found in open water beyond the continental shelf in water deeper than 1,000 m. The whale is rarely found in water less than 200 m deep. Southern bottlenose whales are thought to have a circumpolar distribution in the Southern Hemisphere, south of 30°S (Kaschner 2008). They apparently migrate, and are found in Antarctic waters only during the summer, where they tend to occur within about 120 km of the ice edge. They have been found in groups of as many as twenty-five, but mainly appear to travel in units of less than ten.

76 Ecosystem Modelling of the Chatham Rise

Northridge (1984) and Mead (1989) reported that there were no population estimates or even rough figures on relative abundance of the southern bottlenose whale available at that time. In 1995, Kasamatsu & Joyce (1995) published abundance estimates for south of the Antarctic Convergence (c. 60°S) in January: 599,300 beaked whales, most of which were southern bottlenose whales. Branch & Butterworth (2001a) estimated the population of southern bottlenose whales south of 60°S from two sets of surveys to be nearer 54,000– 72,000. Based on RES modelling (Kaschner 2008) this would imply about 120 southern bottlenose whales in the Chatham Rise region. We assume that southern bottlenose whales are present in the region for 1 month of the year.

Maximum known sizes are 6–7.5 m and weight of 6.9–8.0 t (Shirihai 2002). Lifespan is not known but is estimated to be about 60 y based on size and comparison with other cetaceans. Southern bottlenose whales are thought to take primarily squid (Northridge 1984), but probably also eat fish and possibly some crustaceans. We assume their diet is composed of: 10% demersal fishes; 20% pelagic fishes; 60% squid; 10% macrozooplankton.

Beaked whales Knowledge of beaked whales is particularly scarce. There are more than 20 species of beaked whale globally, at least half of which occur in New Zealand waters. These include spade-toothed beaked whale ( Mesoplodon traversii ), Blainville’s beaked whale ( M. densirostris ), Andrews’ beaked whale (M. bowdoini), Hector’s beaked whale ( M. hectori ), Gray’s beaked whale ( M. grayi ), Cuvier’s beaked whale ( Ziphius cavirostris ), Arnoux’s beaked whale ( Berardius arnuxii ) and Tasman or Shepherd’s beaked whale ( Tasmacetus shepherdi ). We have poor knowledge of the abundance, distribution, population, biology and ecology of these species. The species generally are thought to prefer high slope and canyon habitats where they feed on fish and squid at depths of ca. 1000 m. Sightings of beaked whales is shown in Figure B13; a total of 27 individuals of beaked whales have been sighted over the Chatham Rise.

In the absence of information, we assume that 100 beaked whales are present on the Chatham Rise year-round. A typical weight of 1.2 t and nominal lifespan of 50 y is assumed (Shirihai 2002). Diet is taken as mainly squid (60%) with small pelagic fishes (25%) and macrozooplankton (15%).

Ecosystem Modelling of the Chatham Rise 77

Figure B13: Distribution of sightings of beaked whales in New Zealand waters.

Production Production rates for marine mammals are generally not particularly important parameters in trophic models as they tend to have few direct predators. We use two methods to estimate P/B for cetaceans. First, Banse & Mosher (1980) relate production to animal biomass as: -0.33 P/B=12.9 ·Ms where Ms is the animal weight expressed as an energy equivalent (kcal), and P/B is the annual value (y -1). Fish are reported as having an energy density of about 1 kcal gWW -1 (Schindler et al. 1993). Mammals are likely to have a higher energy content as a result of their fat-rich blubber. Although the biochemical analysis of blubber of whales varies, 60% lipid is likely (Koopman 2007) implying an energy content of about 9 kcal/g. Assuming such high-lipid tissues make up about 40% of the whale’s body weight, we estimate a total energy density for whales of 4.2 kcal/g. This gives P/B for whales of between 0.019 y -1 (blue whale) and 0.26 y -1 (dusky dolphin). Second, the estimated longevity of each whale species is assumed to represent the age by which the chance of mortality is 95% and annual productivity is equal to annual loss due to mortality. This gives P/B for whales of between 0.030 y -1 (blue whale) and 0.13 y -1 (dusky dolphin). We take an average of these values giving overall P/B of 0.05 y-1 (toothed whales and dolphins) and 0.04 y -1 (baleen whales). For comparison, Bradford-Grieve et al. (2003) give P/B for whales off New Zealand as 0.04–0.06 y-1. Jarre-Teichmann et al. (1998) estimated that a trophic compartment of whales and dolphins had a P/B ratio of 0.60 y -1 although this seems very high. Trites (2003) gave a more reasonable range of P/B=0.02–0.06 y -1 for whales (no distinction between baleen and toothed).

78 Ecosystem Modelling of the Chatham Rise

Consumption There are a number of ways to estimate the food requirements of whales. First, studies have obtained daily consumption rates for baleen whales by examining stomach fullness of dead animals, and estimating the number of feedings per day (e.g., Zenkovich 1970). There is a wide range of estimates of daily consumptions because of variations in the amounts in stomach, number feeds per day, and time of sampling relative to feeding. The first method applied in the current study is based on Innes et al. (1986, 1987) and has been used by various workers (e.g., Armstrong & Siegfried 1991; Tamura 2001, 2003). Daily prey -1 0.67 consumption QWW (kgWW d ) is estimated as QWW =0.42 Wkg where Wkg is the average body wet-weight (kg). Prey and predators are taken as having approximately the same carbon:WW ratio. An alternative approach to estimating consumption is based on considerations of the energy requirements of the animals. The standard metabolic rate (SMR: Lasiewski & Dawson 1967) is the resting or basal rate of animals. The relation: SMR (kcal/d)=71.3 W0.892, where W is the animal weight in kg, was given by Irving (1970). This relationship gives values within 20% of that give by Sigurjonsson & Vikingsson (1997) of SMR=206.25 W0.783 . The average daily energy expenditure of animals is often taken as being higher than the SMR if the animals are undergoing exertion such as swimming long distances. Lockyer (1981) estimated that the daily energy expenditure of large baleen whales, averaged over a year, is 1.3 times the SMR, because of the energetic requirements of migration. Lockyer (1981) gives assimilation efficiencies for Antarctic baleen whales of 79– 83%, and we use 80%. We use an average factor of 0.11 gC gWW -1 (wet weight) (Schneider & Hunt 1982) for fish prey items of whales. Crustacean macrozooplankton have a lower carbon content, measured to be 0.048 gC gWW -1 (Weibe 1988). An energy/carbon ratio of 10 kcal gC -1 were used to give carbon requirements where a mixed or fish-based diet is used (Croxall 1987; Lasiewski & Dawson 1967; Schneider & Hunt 1982). For baleen whales, where diet is mainly crustaceans, energy density per gWW is lower (0.93 kcal gWW -1: Lockyer 1987a) which is equivalent to 19.3 kcal gC -1.

We assume our best estimate of food consumption by whales is given by an average of four methods (Lockyer 1981; Innes et al. 1986; Armstrong & Siegfried 1991; Sigurjonsson & Vikingsson 1997). Differences between these methods are of the order of 30%. The values of Q/B for annual average feeding range from 2.7 y -1 (blue whale) to 11 y -1 (dusky dolphin). For comparison, Bradford-Grieve et al. (2003) used a value of Q/B=15 y-1 for hourglass dolphins (4% of weight per day). Toothed whales and dolphins are assumed to feed at the annual rate in the Chatham Rise study area. For baleen whales, annual average consumption rates i.e. the feeding rates which would occur is feeding were evenly spread over the whole year, and must be adjusted to take into account seasonal differences in feeding rates. It is generally assumed that whales do not feed on their migration from the Antarctic to the tropics, or if they do feed, do so at low intensity. Certainly, baleen whales are known to feed more intensively in the Antarctic in summer than at other times of the year. Reilly et al. (2004) and Sigurjonsson & Vikingsson (1997) use the values of Lockyer (1981) for the relative feeding rates in the summer and while in transit. Lockyer (1981) suggested that baleen whales feed intensively in the Antarctic for about 120 d y-1 and consume at a rate 1 th approximately /10 of this at other times of the year. In this case, the Q/B value appropriate for the model (i.e. the rate of feeding while in transit through the Chatham Rise) will be approximately 0.1 times as great as the annual average Q/B value. Overall consumption

Ecosystem Modelling of the Chatham Rise 79

rates on the Chatham Rise are hence estimated as 8.2 y -1 (toothed whales and dolphins) and 0.6 y -1 (baleen whales).

Diet The diet of the groups of “toothed whales and dolphins” and “baleen whales” is estimated by summing diet fractions (see individual section on species) in proportion to estimated annual consumptions. Overall, toothed whales and dolphin diet is estimated to be: 25% small pelagic fishes, 5% large pelagic fishes, 7% demersal fishes, 60% squid, 2% zooplankton and 1% dolphins. Baleen whale diet is estimated to be: 16% small pelagic fishes, 1% squid, 67% crustacean macrozooplankton, 6% gelatinous zooplankton and 10% mesozooplankton.

Other information: P/Q, EE, U, accumulation, imports, exports, transfers In the work presented, we assume that long-term changes in biomass per year are small for all species of whale (Trites et al. 2004).

We assume that the carbon content of toothed and baleen whales in the Ross Sea is 10% of wet weight (0.1 gC/gWW), the same carbon content as fish (Vinogradov 1953), following previous trophic modelling work (e.g., Bradford-Grieve et al. 2003). Lockyer (1981) gives assimilation efficiencies for Antarctic baleen whales of 79–83%, and we use 80%. Ecotrophic efficiency of cetaceans is close to zero as most mortality is not due to predation. Instead, dead cetaceans in the model are channelled to carcasses.

80 Ecosystem Modelling of the Chatham Rise

Summary of data

Table B1: Data and parameters for the cetaceans component of the Chatham Rise trophic model

Prop - Chatham Ind weight ortion Months, Longevity Biomass Annual Rise Q/B Group Species Name (kg) Number S (%) M (y) (tWW) P/B (y -1) Q/B (y -1) (y -1) Toothed whales & dolphins Physeter macrocephalus Sperm whale 27000 107 100 3 65 722 0.04 5.2 5.2 (Odontoceti) Globicephala melas, G. macrorhynchus Pilot whale 1800 331 100 6 53 298 0.06 10.6 10.6 Delphinus delphis Common dolphin 90 2460 100 3 25 56 0.15 23.7 23.7 Orcinus orca Killer whale 3020 1000 10 6 50 151 0.06 9.2 9.2 Lagenorhynchus obscurus Dusky dolphin 80 550 100 1 22.5 4 0.16 24.5 24.5 Tursiops truncatus Bottlenose dolphin 120 100 100 1 47 1 0.12 21.9 21.9 Pseudorca crassidens False killer whale 1500 100 100 1 50 13 0.07 11.1 11.1 Ziphiidae Beaked Odontoceti 1300 100 100 12 50 130 0.07 11.1 11.1 Hyperoodon planifrons Southern bottlenose whale 7500 120 100 1 60 75 0.05 7.1 7.1

Baleen whales Eubalaena australis Right whale 25000 30 50 6 70 188 0.04 4.0 0.4 (Mysticeti) Balaenoptera bonaerensis Minke whale 4800 172 0 100 1 61 808 0.05 6.5 0.7 Balaenoptera musculus Blue whale 103000 6 100 1 100 52 0.02 2.9 0.3 Balaenoptera borealis Sei whale 16800 59 100 1 69 83 0.04 4.5 0.4 Megaptera novaeangliae Humpback whale 30000 45 100 1 75 113 0.03 4.2 0.4

Ecosystem Modelling of the Chatham Rise 81

References Ainley, D.G. (1985). Biomass of birds and mammals in the Ross Sea, Antarctica. Pp. 498-515 in W.R. In: Siegfried; P, W.R.; Condy and, P.R.; Laws, R.M. Laws (eds) Antarctic nutrient cycles and food webs. Berlin, Springer-Verlag, Hamburg. Pp. 498-510.

Armstrong, A.J.; Siegfried, W.R. (1991). Consumption of Antarctic krill by minke whales. Antarctic Science 3(1): 13-18.

Arnold, P.; Marsh, H.; Heinsohn, G. (1987). The occurrence of two forms of minke whales in east Australian waters with a description of the external characters and skeleton of the diminutive or dwarf form. The Scientific Reports of the Whales Research Institute 38: 1-46.

Baker, C.S.; Clapham, P.J. (2004). Modelling the past and future of whales and whaling. Trends in Ecology and Evolution 19(7): 365-371.

Baker, A.N., (1990). Marine mammals. In: Glasby, G.P. (Ed.), Antarctic sector of the Pacific. Elsevier Oceanogr. Ser. 51, Amsterdam, pp 241-262.

Banse, K., Mosher, S., (1980). Adult body size and annual production / biomass relationships of field populations. Ecol. Monogr. 50, 355-379.

Berzin, A.A., (1972). The Sperm Whale. Israel Program for Scientific Translations, Jerusalem.

Best, P.B. (1985). External characters of southern minke whales and the existence of a diminutive form. The Scientific Reports of the Whales Research Institute 36: 1-33.

Best, P.B.; Schell, D.M. (1996). Stable isotopes in southern right whales (Eubalaena australis) baleen as indicators of seasonal movements, feeding and growth. Marine Biology 124: 483–494.

Bradford-Grieve, J.M., Probert, P.K., Nodder, S.D., Thompson, D., Hall, J., Hanchet, S., Boyd, P., Zeldis, J., Baker, A.N., Best, H.A., Broekhuizen, N., Childerhouse, S., Clark, M., Hadfield, M., Safi, K. and Wilkinson, I. (2003). Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology 289: 223-262.

Branch, T.A.; Butterworth, D.S. (2001a). Estimates of abundance south of 60ºS for cetacean species sighted frequently on the 1978/79 to 1997/98 IWC/IDCR- SOWER sighting surveys. Journal of Cetacean Research and Management 3(3): 251-70.

Branch, T.A. (2006). Humpback abundance south of 60°S from three completed sets of IDCR/SOWER circumpolar surveys. IWC Paper SC/A06/HW6:14pp.

Ecosystem Modelling of the Chatham Rise 82

Branch, T.A. (2008). Abundance of Antarctic blue whales south of 60°S from three complete circumpolar sets of surveys. Journal of Cetacean Research and Management 9: 253-262.

Branch, T.A.; Stafford, K.M.; Palacios, D.M. & 39 others. (2007). Past and present distribution, densities, and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean. Mammal Review, 37: 116- 175.

Brown, S.G. (1986). Twentieth-century records of right whales (Eubalaena glacialis) in the northeast Atlantic Ocean. Report of the International Whaling Commission Special Issue 10: 121–127.

Brown, S.G., Lockyer, C.H., (1984). Whales. In: R.M. Laws (Ed.). Antarctic Ecology. Vol 2. Academic Press, London, pp: 717-781.

Cipriano, F. and Webber, M. (2010). Dusky dolphin life history and demography. Pp. 21-48 in: Würsig, B., and Würsig, M., editors. The Dusky Dolphin: Master Acrobat off Different Shores. San Diego, CA: Elsevier, Inc.

Clarke, M.R. (1980). Cephalopoda in the diet of sperm whales of the Southern Hemisphere and their bearing on sperm whale biology. Discovery Reports 37: 1- 324.

Constantine, R.; Brunton, D.H.; Baker, C.S. (2003). Effects of tourism on behavioural ecology of bottlenose dolphins in northeastern New Zealand. DOC Science Internal Series 123. Department of Conservation, Wellington. 26 p.

Croxall, J.P. (1987). Seabirds: feeding ecology and role in marine ecosystems. Cambridge University Press, pp 408.

Cummings, W.C. (1985). Right whales Eubalaena glacialis (Muller, 1776) and Eubalaena australis (Desmoulins, 1822). Pp. 275-304 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 3 The sirenians and baleen whales. Academic Press.

Dawbin, W.H. (1986). Right whales caught in waters around south eastern Australia and New Zealand during the nineteenth and early twentieth centuries. Report of the International Whaling Commission Special Issue 10: 261–267.

Dawson, S. (1985). The New Zealand whale and dolphin digest: The official Project Jonah guidebook. Auckland, New Zealand: Brick Row Publishing Co. Ltd. 130 pp.

Evans, K.; Hindell, M.A. (2004). The diet of sperm whales (Physeter macrocephalus), in southern Australian waters. ICES Journal of Marine Science 61(8): 1313-1329.

Ecosystem Modelling of the Chatham Rise 83

Evans, W.E. (1994). Common dolphin, White-bellied Porpoise Delphinus delphis Linnaeus, 1758. In: Ridgway, S.H. & R. Harrison, eds. Handbook of Marine Mammals Vol 5: The First Book of Dolphins. Page(s) 191-224. Academic Press, London.

Gaskin, D.E. (1973). Sperm whales in the western South Pacific. New Zealand Journal of Marine and Freshwater Research 7: 1-20.

Gaskin, D.E. (1982). The ecology of whales and dolphins. Heinemann, London, 459 pp.

Gerrodette, T.; Watters, G.; Perryman, W.; Balance, L. (2008). Estimates of 2006 dolphin abundance in the eastern tropical Pacific, with revised estimates from 1986-2003.. NOAA-TM-NMFS-SWFSC-422.

Halliday, J.; L.G. Torres; J. Sturman (2011). Data on distribution patterns of cetaceans on the Chatham Rise. NIWA report WLG2011-8. Pp 18.

Hammond, P.S.; Bearzi, G.; Bjørge, A.; Forney, K.; Karczmarski, L.; Kasuya, T.; Perrin, W.F.; Scott, M.D.; Wang, J.Y.; Wells, R.S.; Wilson, B. (2008). Delphinus delphis. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1.

Hamner, W.M.; Stone, G.S.; Obst, B.S. (1988). Behavior of southern right whales, Eubalaena australis, feeding on the Antarctic krill, Euphasia superba. Fisheries Bulletin 86: 143–150. IWC (2001)

Ichii, T.; Kato, H. (1991). Food and daily food consumption of southern minke whales in the Antarctic. Polar Biology, 11: 479–487.

Innes, S.; Lavigne, D.M.; Kovacs, K.M. (1987). Feeding rates of seals and whales. Journal of Animal Ecology, 56: 115-130.

Innes, S.; Lavigne, D.M.; Earle, W.M.; Kovacs, K.M. (1986). Estimating feeding rates of marine mammals from heart mass to body mass ratios. Marine Mammal Science, 2: 227-229.

International Whaling Commission (1980). Report of the International Whaling Commission 30.

International Whaling Commission (1984). Report of the minke whale ageing workshop. Report of the International Whaling Commission, 34: 675-699.

International Whaling Commission, (2000). Report of the Scientific Committee, Annex G. Report of the Subcommittee on the Comprehensive Assessment of Other Whale Stocks. Journal of Cetacean Research Management 2(suppl.): 167- 208.

International Whaling Commission (2001). Report of the sub-committee on the comprehensive assessment of whale stocks-other stocks. Journal of Cetacean Research and Management (Special Issue) 3: 209-228.

84 Ecosystem Modelling of the Chatham Rise

Irving L. (1970). Morpho-physiological adaptations in marine mammals for life in polar areas. In: M.W. Holdgate (ed.), Antactic Ecology. Vol. 1. Academic Press, London, pp. 455–463.

IUCN, (2007). World Conservation Union assessments, available at: http://www.iucn.org/

IUCN, (2005). World Conservation Union assessments, available at: http://www.iucn.org/

Jarre-Teichmann, A., Shannon, L.J., Moloney, C.L., Wickens, P.A., (1998). Comparing trophic flows in the southern Benguela to those in other upwelling ecosystems. S. Afr. J. Mar. Sci. 19, 391-414.

Jefferson T.A.; Leatherwood, S.; Webber, M.A. (1993). FAO Species identification guide. Marine mammals of the world. UNEP / FAO, Rome, 320 pp.

Kasamatsu, F.; Joyce, G.G. (1995). Current status of Odontocetes in the Antarctic. Antarctic Science, 7(4): 365-379.

Kasamatsu, F.; Nishiwaki, S.; Ishikawa, H. (1995). Breeding areas and southward bound migrations of southern minke whales Balaenoptera acutorostrata. Marine ecology Progress Series 119: 1-10.

Kaschner, K. (2004). Modelling and Mapping Resource Overlap between Marine Mammals and Fisheries on a Global Scale. PhD thesis. The University of British Columbia, Canada.

Kawamura, A. (1974). Food and feeding ecology in the southern sei whale. Scientific Reports of the Whales Research Institute, Tokyo 26: 25-144, 3 pls.

Kenney, R.D. (2002). "North Atlantic, North Pacific and Southern Right Whales". In William F. Perrin, Bernd Wursig and J. G. M. Thewissen. The Encyclopedia of Marine Mammals. Academic Press. pp. 806–813.

Klinowska, M. (1991). Dolphins, Porpoises and Whales of the World. The IUCN Red Data Book. IUCN, Gland, Switzerland.

Knox, G.A. (2007). Biology of the Southern Ocean. Boca Raton, CRC Press. 2nd edition, 621 pp.

Konishi, K.; Tamura, T.; Zenitani, R.; Bando, T.; Kato, H.; Walløe, L. (2008). Decline in energy storage in the Antarctic minke whale (Balaenoptera bonaerensis) in the Southern Ocean. Polar Biology 31: 1509-1520.

Koopman, H.N. (2007). Phylogenetic, ecological, and ontogenetic factors influencing the biochemical structure of the blubber of odontocetes. Marine Biology 151: 277–291.

Lasiewski, R.C.; Dawson, W.R. (1967). A re-examination of the relation between standard metabolic rate and body weight in birds. Condor, 69: 13-23.

Ecosystem Modelling of the Chatham Rise 85

Laws, R.M. (1977). Seals and whales of the Southern Ocean. Philosophical Transactions of the Royal Society of London B, 279: 81-96.

Leatherwood, S.; Reeves, R.R. (1983). Abundance of bottlenose dolphins in Corpus Christi Bay and coastal southern Texas. Contributions in Marine Science, 26: 179-199.

Lockyer, C. (1976). Body weights of some species of large whales. Journal du Conseil International pour l’Exploration de la Mer, 36: 259–273.

Lockyer, C. (1981a). Growth and energy budgets of large baleen whales from the Southern Hemisphere. In: Mammals in the Seas. Vol. III, General Papers and Large Cetaceans. FAO Fisheries Series, pp. 379–487.

Lockyer, C. (1981b). Estimates of growth and energy budget for the sperm whale Physeter catodoc. In: Mammals in the Sea, vol. 3, Rome, FAO 489-504.

Lockyer, C.H.; Brown, S.G. (1981). The migration of whales. In: Aidley, D.J. (ed.) Animal Migration, Cambridge University Press, Cambridge, 105-137.

Mackintosh, N.A. (1965). The stocks of whales. London, Fishing News (Books) Ltd., 232p.

Markowitz, T.M. (2004). Social organization of the New Zealand dusky dolphin. Ph.D. dissertation, Texas A&M University, College Station.

Markowitz, T.M., Harlin, A.D., Würsig, B., and McFadden, C.J. (2004). Dusky dolphin foraging habitat: overlap with aquaculture in New Zealand. Aquatic Conservation: Marine and Freshwater Ecosystems 14: 133-149.

McNab, R. (1913). The Old Whaling Days: a history of southern New Zealand from 1830 to 1840. Whitcombe & Tombs, Christchurch.

Mead, J.G. (1989). Bottlenose whales - Hyperoodon ampullatus (Forster, 177) and Hyperoodon planifrons Flower, 1882. In: Handbook of Marine Mammals (Ridgway SH, Harrison SR eds.) Vol. 4: River Dolphins and the Larger Toothed Whales. Academic Pres, London, pp. 321-348.

Meynier L, Pusineri C, Spitz J, Santos MB, Pierce GJ, Ridoux V (2008) Intraspecific dietary variation in the short-beaked common dolphin Delphinus delphis in the Bay of Biscay: importance of fat fish. Mar Ecol Prog Ser 354: 277-287.

Nemoto, T.; Okiyama, M.; Takahashi, M. (1985). Aspects of the roles of squid in food chains of marine Antarctic ecosystems. In: W.R. Siegfried, P.R. Condy & R.M. Laws (eds) Antarctic Nutrient Cycles and Food Webs . Berlin, Springer Verlag, 700 pp. [Proceedings of the 4th SCAR/SCOR/IUBS/ IABO/SASCAR Symposium on Antarctic Biology, Wilderness, South Africa, 12-16 September 1983.]

Northridge, S.P. (1984). World Review of Interactions Between Marine Mammals and Fisheries. Food and Agriculture Organization Fisheries Technical Paper 251.

86 Ecosystem Modelling of the Chatham Rise

Nowak, R.M. (1999). Walker’s Mammals of the World. Baltimore: Johns Hopkins University Press.

Ohsumi, S.; Kasamatsu, F. (1986). Recent off-shore distribution of the southern right whale in summer. Report of the International Whaling Commission Special Issue 10: 177–185.

Olsen, E.; Holst, J.C. (2001). A note on common minke whale (Balaenoptera acutorostrata) diets in the Norwegian Sea and the North Sea. Journal of Cetacean Research and Management 3(2):179–183.

Patenaude, N.J. (2003).Sightings of southern right whales around ‘mainland’ New Zealand. Science for Conservation 225, Department of Conservation, Wellington, New Zealand .

Perry, S.L.; DeMaster. D.P.; Silber, G. (1999). The great whales: history and status of six species listed as endangered under the U.S. Endangered Species Act of 1973. Marine Fisheries Review (Special Issue) 61(1): 1-74.

Pinkerton, M.H.; J.M. Bradford-Grieve; S.M. Hanchet (2010). A balanced model of the food web of the Ross Sea, Antarctica. CCAMLR Science, 17: 1–31.

Pitman, R.L.; Ensor, P. (2003). Three different forms of killer whales in Antarctic waters. Journal of Cetacean Research and Management, 5(2): 131-139.

Reilly, S.; Hedley. S.; Borberg, J.; Hewitt, R.; Thiele, D.; Watkins, J.; Naganobu, M. (2004). Biomass and energy transfer to baleen whales in the South Atlantic sector of the Southern Ocean. Deep Sea Research II, 51: 1397-1409.

Rice, D.W. (1998). Marine mammals of the world: systematics and distribution. Society for Marine Mammalogy, Special Publication Number 4 (Wartzok D, Ed.), Lawrence, KS. USA.

Saino, N.; Guglielmo, L. (2000). ROSSMIZE expedition: distribution and biomass of birds and mammals in the western Ross Sea. p. 469-478. In: F.M. Faranda et al. (ed.) 2000. Ross Sea ecology: Italianartide Expeditions (1987-1995). New York. Springer-Verlag.

Scarff, J.E. (1986). Historic and present distribution of the right whale (Eubalaena glacialis) in the Eastern North Pacific south of 50oN and east of 180oW. Report of the International Whaling Commission Special Issue 10: 43–63.

Schindler, D.E., Kitchell, J.F., Xi He, Carpenter, S.R., Hodgson, J.R., Cottingham, K.L., (1993). Food web structure and phosphorus cycling in lakes. Trans. Am. Fish. Soc. 122, 756-772.

SeaMap, (2005). Available at http://seamap.env.duke.edu.

Ecosystem Modelling of the Chatham Rise 87

Shelton, D.E.; Harlin-Cognato, A.D.; Honeycutt, R.L.; Markowitz, T.M. (2010). Sexual segregation and genetic relatedness in New Zealand. Pp. 177-209 in: Würsig, B., and Würsig, M., editors. The Dusky Dolphin: Master Acrobat off Different Shores. San Diego, CA: Elsevier, Inc.

Shirihai, H. (2008). The Complete Guide to Antarctic Wildlife, Second Edition. Princeton University Press, pp 544.

Shirihai, H.; Jarrett, B. (2006). Whales Dolphins and Other Marine Mammals of the World. Princeton: Princeton Univ. Press. pp. 155–161. ISBN 0-691-12757-3. Shirihai, H. 2008. The Complete Guide to Antarctic Wildlife, Second Edition. Princeton University Press, pp 544.

Sigurjónsson, J., Víkingsson, G.A., (1998). Seasonal abundance of an estimated food consumption by cetaceans in Icelandic and adjacent waters. Journal of Northwestern Atlantic Fisheries Science, 22: 271-287.

Širovi ć, A.; Hildebrand, J.A.; Wiggins, S.M. (2009). Blue and fin whale acoustic presence around Antarctica during 2003 and 2005. Marine Mammal Science 25: 125-136.

Skaug, H.J.; Gjosaeter, H.; Haug, T.; Nilssen, K.T.; Lindstrom, U. (1997). Do minke whales (Balaenoptera acutorostrata) exhibit particular prey preferences? Journal of Northwestern Atlantic Fisheries Science, 22: 91-104.

Stewart, B.S.; Leatherwood, S. (1985). Minke whale. In: Ridgway, S.H.; Harrison, R. (eds). Handbook of marine mammals. Vol. 3. London, Academic Press. Pp 91- 136.

Stockin, K.A.; Lusseau, D.; Binedell, V.; Orams, M.B. (2008a). Tourism affects the behavioural budget of common dolphins (Delphinus sp.) in the Hauraki Gulf, New Zealand. Marine Ecology Progress Series, 355: 287–295.

Stockin, K.A.; Pierce, G.J.; Binedell, V.; Wiseman, N.; Orams, M.B. (2008b). Factors affecting the occurrence and demographics of common dolphins (Delphinus sp.) in the Hauraki Gulf, New Zealand. Aquatic Mammals 34(2), 200-211.

Stockin, K.A.; Visser, I.N. (2005). Anomalously pigmented common dolphins (Delphinus sp.) off Northern New Zealand. Aquatic Mammals 31(1): 43-51.

Tamura, T. (2001). Competition for food in the ocean: man and other apical predators. Responsible Fisheries in the Marine Ecosystem, Reykjavík 30 Sep – 4 Oct 2001.

Tamura, T. (2003). Regional assessments of prey consumption and competition by marine cetaceans in the world. In: Responsible Fisheries in the Marine Ecosystem, eds: M. Sinclair and G. Valdimarsson, FAO, 143-170.

Tomilin, A.G. (1957). Cetacea. In: Mammals of the USSR and adjacent countries. Vol.9, S.I. Ognev (ed.). Jerusalem, Israel Program for Scientific Translations, IPST Cat.No. 1124, 1967.

88 Ecosystem Modelling of the Chatham Rise

Tormosov, D.D.; Mikhaliev, Y.A.; Best, P.B.; Zemsky, V.A.; Sekiguchi, K.; Brownell- Jr. R.L. (1998). Soviet catches of southern right whales Eubalaena australis, 1951–1971. Biological data and conservation implications. Biological Conservation 86: 185–197.

Townsend, C.H. (1935). The distribution of certain whales as shown by logbook records of American whaleships. Zoologica, 19: 1–50.

Trites, A.W.; Pauly, D. (1998). Estimating mean body masses of marine mammals from maximum body lengths. Canadian Journal of Zoology, 76: 886-896.

Trites, A.W. (2003). Food webs in the ocean: who eats whom and how much? In: Responsible Fisheries in the Marine Ecosystem, M. Sinclair; G. Valdimarsson (eds.), FAO, 125-141.

Vinogradov, A.P. (1953). The elementary chemical composition of marine organisms. Memoir of the Sears Foundation for Marine Research, Yale University, New Haven II, 647 pp.

Warneke, R.M. (2001). Cetacean strandings in Cook Strait (New Zealand) in relations to the inter-island subsea HVDC cable. Report to National Grid, Australia. Available at: www.nationalgrid.com.au. 25 p.

Webb, B.F. (1973). Dolphin sightings, Tasman Bay to Cook Strait, New Zealand, September 1968 to June 1969. New Zealand Journal of Marine and Freshwater Research, 7(4): 399–405.

Weibe, P.H., (1988). Functional regression equations for zooplankton displacement volume, wet weight, dry weight, and carbon: a correction. Fish. Bull. 86(4), 833- 835.

Wells, R.; Scott, M. (2002). Bottlenose Dolphins. In Perrin, W.; Wursig, B. and Thewissen, J.. Encyclopedia of Marine Mammals. Academic Press. pp. 122–127. ISBN 0-12-551340-2.

Whitehead, H. (2002). Estimates of the current global population size and historical trajectory for sperm whales. Marine Ecology Progress Series, 242: 295-304.

Whitehead, H. (2003). Sperm whales: social evolution in the ocean. Chicago, IL: University of Chicago Press.

Whitehead, H.; Weilgart, L. (2000). The Sperm Whale: Social females and roving males. In: Mann, J.; Connor, R.C.; Whitehead, H., editors. Cetacean Societies: Field studies of dolphins and whales. Chicago: University of Chicago Press. p. 154-172.

Woodley, T.H.; Gaskin, D.E. (1996). Environmental characteristics of North Atlantic right and fin whale habitat in the lower Bay of Fundy, Canada. Canadian Journal of Zoology 74: 75–84.

Ecosystem Modelling of the Chatham Rise 89

Würsig, B.; Duprey, N.; Weir, J. (2007). Dusky dolphins (Lagenorhynchus obscurus) in New Zealand waters. Present knowledge and research goals. DOC Research and Development Series 270: 1-28.

Young, J.W. (2000). Do large whales have an impact on commercial fishing in the south Pacific Ocean? Journal of International Wildlife Law and Policy, 3(3): 253- 275.

Zenkovich, B.A. (1970). Whales and plankton in Antarctic waters. In: Holdgate MW (ed) Antarctic ecology. Academic Press, London, p 183–185.

90 Ecosystem Modelling of the Chatham Rise

Appendix C Seals

Introduction This group includes eared (otariids) and earless (phocids) seals in the study area. Two species of seal occur in the study area: New Zealand fur seal ( Arctocephalus forsteri ) and Hooker’s (New Zealand) sealion ( Phocarctos hookeri ). Although southern elephant seals Mirounga leonine ) have been seen in the New Zealand region, this species is unlikely to reach as far north as the Chatham Rise on a regular basis (Shirihai 2008).

New Zealand fur seal The New Zealand fur seal ( Arctocephalus forsteri ) is now found in breeding colonies on the islands and coasts of New Zealand. Numbers in New Zealand have increased and their breeding distribution has expanded northward through recent decades after extirpation attributable to Polynesian subsistence hunting (Smith 2005, 2011) followed by European commercial sealing in the late 18th and early 19th centuries (Lalas & Bradshaw 2001; Ling 2002; Richards 1994). Currently, NZ fur seals are dispersed throughout New Zealand waters, especially in waters south of about 40°S to Macquarie Island (Ministry for Primary Industries, 2012). In the most comprehensive attempt to quantify the total NZ fur seal population, Wilson (1981) summarised population surveys of mainland New Zealand and offshore islands undertaken in the 1970s and estimated the population size within the New Zealand region at between 30,000 and 50,000 animals. Since then, several authors have suggested a population size of ~100,000 animals (Taylor 1990, see Harcourt 2001), but this estimate is very much an approximation and its accuracy is difficult to assess in the absence of comprehensive surveys. Recent estimates of the fur seal population of the Otago coast are 20,000–30,000 (Chris Lelas, pers. comm.). This estimate includes stocks of about 9,600 individuals on Auckland, Campbell, Bounty and Antipodes Islands on the Southern Plateau (Crawley & Warneke, 1979). We use a New Zealand population estimate of 40,000 New Zealand fur seals.

The proportion of the population and the proportion of time fur seals spent foraging in the Chatham Rise study region is not well known. The seasonal distribution of the New Zealand fur seals is determined by the sex and maturity of each animal (Ministry for Primary Industries, 2012). Satellite tracking of adult female, breeding New Zealand fur seals shows that they may forage up to 200 km beyond the continental slope, into water deeper than 1000 m. The 250 m depth contour (nearest Chatham Rise study area boundary to land) is about 100 km away from the coast so fur seals are likely to be able penetrate into the study area. Adult male New Zealand fur seals are generally at the breeding colonies from late October to late January (4 months per year) then move to haulout areas around the New Zealand coastline (see Bradshaw et al. 1999; Crawley & Wilson 1976). Females arrive at the breeding colony from November and lactating females remain at the colony (apart from short foraging trips) for about 10 months until the pups are weaned, usually during August–September (Crawley & Wilson 1976). Non-breeders are dispersed at sea, at haulouts or at breeding colony periphery year round. New Zealand fur seals are annual breeders and generally produce one pup after a gestation period of about 10 months (Crawley & Wilson 1976). Boren (2005) reported a fecundity rate of 62% for a Kaikoura colony, similar to the 67% estimated by Goldsworthy & Shaughnessy (1994) for a South Australian colony.

Ecosystem Modelling of the Chatham Rise 91

Evidence of the number of New Zealand fur seals in the study area comes from fisheries bycatch. The spatial and temporal overlap of commercial fishing grounds and New Zealand fur seal foraging areas has resulted in New Zealand fur seal captures in fishing gear (Mattlin 1987, Rowe 2009). New Zealand fur seals are caught during bottom and midwater trawl operations, particularly for hoki ( Macrourus novazelandiae ), squid ( Nototodarus spp.) and southern blue whiting ( Micromesistius australis ) around the coastline of South Island and the offshore islands in the southern waters of the New Zealand EEZ (Baird 2005). There is a by- catch of New Zealand fur seals in the western hoki fishery on the Chatham Rise (Ministry for Primary Industries, 2012).

We hence estimate that of the order of 6% of their food is likely to come from the Chatham Rise area and adjust the numbers in the study region pro rata. The annual average equivalent number of fur seals in the study region is 2550 seals. Adult males weigh 120–200 kg and adult females 40–70 kg (Shirihai 2008). New born pups weight about 3.6 kg (Shirihai 2008). Assuming a 50:50 sex ratio and using an average weight for males and females, the annual wet biomass-equivalent in the study area is 274 t.

Measurements of the body composition of Antarctic fur seals (Arnould et al. 1996), show that ash-free dry weight is approximately 35% of wet-weight. Assuming that ash-free dry weight is composed of material in approximately carbohydrate proportions (C 6H12 O6) gives 0.15 gC/ gWW which we use here. Other authors have used 0.1 gC /gWW for seals (e.g. Bradford- Grieve et al. 2003). The maximum age recorded for New Zealand fur seals in New Zealand waters is 22 years for females (Dickie & Dawson 2003) and 15 years for males (Mattlin 1978).

Diet of fur seals on the Chatham Rise is not well known. However, dietary studies of New Zealand fur seals have been conducted at colonies in Nelson-Marlborough, west coast South Island, Otago Peninsula, Kaikoura, Banks Peninsula, Snares Islands, and off Stewart Island, and summaries are provided by Carey (1992), Harcourt (2001), Boren (2010), and Baird (2011). New Zealand fur seals are opportunistic foragers and, depending on the time of year, method of analysis, and location, their diet includes at least 61 taxa (Holborow 1999) of mainly fish (particularly lanternfish, myctophids), as well as anchovy ( Engraulis australis ), aruhu ( Auchenoceros punctatus ), barracouta ( Thrysites atun ), hoki ( Macruronus novaezelandiae ), jack mackerel ( Trachurus spp.), pilchard ( Sardinops sagax ), red cod (Pseudophycis bachus ), red gurnard ( Chelidonichthys kumu ), silverside ( Argentina elongate ), sprat ( Sprattus spp.) and cephalopods (octopus ( Macroctopus maorum), squid ( Nototodarus sloanii , Sepioteuthis bilineata )) (see Harcourt et al. 1995, Mattlin et al. 1998, Fea et al. 1999). Diets are likely to vary by area and season. For example, at Open Bay Islands in summer, the relatively shallow dives and nocturnal feeding suggest feeding on pelagic and vertical migrating prey species like arrow squid; deeper dives and increased number of dives in daylight during autumn and winter suggested that the prey species may include benthic, demersal, and pelagic species (Mattlin et al. 1998; Harcourt et al. 2002).

92 Ecosystem Modelling of the Chatham Rise

Hooker’s (New Zealand) sealion Hooker’s sealion ( Phocarctos hookeri ) is New Zealand’s only endemic seal. The main breeding colonies (95% pups born) are on Auckland Islands, where the total population is probably about 12,000, (Breen & Kim 2006a,b; Breen et al. 2010; Breen 2003; Gales & Fletcher, 1999). In addition, about 200 individuals breed on the Otago coast (Chris Lalas, pers. comm.); breeding began in 1994, with numbers increasing at about 10% annually.

The proportion of time sea-lions spent foraging in the Chatham Rise study region is not well known. Hooker’s sealion are caught incidentally around the Auckland Islands in the southern squid trawl fishery (Ministry of Primary Industries, 2012). However, despite considerable observation from fishing vessels in the Chatham Rise area, no interactions with sealions have been observed in the region (Ministry for Primary Industries, 2012). Foraging distance from shore for adult female sealions from the Auckland Islands from satellite tracking are 102 km (maximum of 175 km), with maximum time spent foraging at sea 66 h; average dive depth is 129 m (maximum of 597 m) (see Table 3.1, Ministry for Primary Industries, 2012). Females breeding on the Otago coast stay very local with shorter foraging distances and times (Ministry for Primary Industries 2012). Males and non-breeding sealions are likely to be more widely dispersed at sea. It is hence unlikely that more than a very small proportion of sealions forage on the Chatham Rise study area. We assume that 0.2% of the population forages in the study region (equivalent to 12 sealions), and reduce annual equivalent biomass pro rata.

Males are reported to weigh about 350 kg and females 110 kg (Gales, 1995), a little less than that given by Shirihai (2008) of 320–450 kg (adult males) and 90–230 kg (adult females). New born pups weight about 7.5 kg (Shirihai 2008). The mean mass of adult female sealions at the Auckland Islands was 112 kg (Ministry for Primary Industries, 2012). We hence estimate an equivalent average annual wet biomass in the study area of 3 tonnes. We take carbon as 15% wet weight. The maximum recorded age is 23 years for males and 18 for females (www.teara.govt.nz).

Hooker’s sealion take a broad variety of prey, mainly small fish, cephalopods (especially octopus), crustaceans (including crabs, crayfish and prawns), and occasionally, penguins. Hooker’s sealions are generalist predators with a varied diet that includes fish (rattail, red cod, opalfish, hoki), cephalopods (octopus, squid), crustaceans (lobster krill, scampi), and salps (Cawthorn et al. 1985; Childerhouse et al. 2001; Meynier et al. 2009). Off Otago, the diet of sealions is made up of octopus (typically 2–5 kg), 20-30%; teleost fishes (to 10 kg), 20–30%; cartilaginous fishes (to 5 kg), 20–30%; swimming crabs, 5%; fur seal (for large males, only), c. 10%; arrow squid, 1-5% (Chris Lelas pers. comm.).

Production Production rates for marine mammals are generally not particularly important parameters in trophic models as they tend to have few direct predators. We use two methods to estimate P/B for seals. First, we estimated production following Banse & Mosher (1980) who related -0.33 production to animal biomass as: P/B=12.9 ·Ms where Ms is the animal weight expressed as an energy equivalent (kcal), and P/B is the annual average equivalent value (y -1). Mammals are likely to have a higher energy content than fish (c. 1 kcal gWW -1). Although the biochemical analysis of blubber varies, 60% lipid is likely (Koopman 2007) implying an energy content of about 9 kcal g-1. Assuming such high-lipid tissues make up about 20% of

Ecosystem Modelling of the Chatham Rise 93

seals’ body weights, we estimate a total energy density of 2.6 kcal g-1. ). Second, the estimated longevity of each seal species is assumed to represent the age by which the chance of mortality is 95% and annual productivity is equal to annual loss due to mortality. These methods differ by less than 10%. We take an average of these values giving overall P/B of 0.20 y-1 (New Zealand fur seal) and 0.15 y-1 (Hooker’s sealion). For the seal group as a whole, we estimate P/B=0.20 y-1.

Consumption Seal energetics have been reviewed by Lavigne et al. (1982, 1986), and a summary is given by Knox (2007). We estimated food consumption requirements for both species of seals were estimated by three methods, using an average of all three methods as our best estimate. These were then combined between species in relation to biomass. Nagy (1987) estimated daily dry weight food consumption for eutherian mammals (with placenta) 0.822 according to body weight as Qd=0.235 W , where Qd is the daily consumption in g dry weight; W is the animal weight (g). Dry weight of prey items was converted to carbon using a ratio of 0.3 gC gDW -1 (Vinogradov 1953). An estimate of oxygen consumption of a southern elephant seal by Hindell & Lea (1998) suggested that Nagy’s (1994) equation may overestimate field metabolic rate. In the second and third methods, consumption of seals was estimated based on the amount of food they require to supply sufficient energy to satisfy their standard metabolic rate (SMR). There is conflicting evidence on whether the metabolic rate of seals is significantly greater than that of terrestrial mammals of a similar size in natural (i.e. non-captive) conditions (e.g., Riedman 1990, and references therein). Some studies have shown metabolic rates for seals in cold-regions to be 1.5–3 times higher than terrestrial mammals in temperate regions (e.g., Costa et al. 1986). Other work found that metabolic rates of seals were only slightly higher (1.1–1.2 times) than those of a terrestrial mammal of similar size (see Riedman 1990). Here, we used the relation: SMR (kcal d-1) = 71.3·W 0.892 , where W is the animal weight in kg which was developed for marine mammals in polar areas (Irving 1970). The third method used SMR= 70.5·W 0.7325 (Lockyer 1981). In both cases, the average daily energy requirement of seals was taken as 2.8 times the standard metabolic rate (Lasiewski & Dawson 1967). An assimilation efficiency of 0.8 and energy/carbon ratio of ~10 kcal gC -1 were used to give carbon requirements (Croxall 1987; Lasiewski & Dawson 1967; Schneider & Hunt 1982). The latter figure is appropriate for fish, and we recognize that squid has a somewhat lower energy density relative to carbon than fish (e.g., van Franeker et al. 1997, and references therein). The overall estimate of consumption rates is hence Q/B=19 y -1 (fur seal) and 16 y -1 (Hooker’s sea lion). These are equivalent to 5.5 kg day -1 (fur seal) and 10.2 kg day -1 (Hooker’s sea lion). Consumption for the seal group is estimated to be Q/B=19 y-1. For comparison, other work reports daily food intake for captive seals as 10% of body weight (Laws 1984), and 3.3% for harp seals (Nordoy et al. 1995). These imply Q/B values of between 12–37 y -1, assuming seals and their prey have the same carbon to wet weight ratio. Jarre-Tiechmann et al. (1998) estimate that Cape fur seals have a Q/B ratio of 19 y -1. Bradford-Grieve et al. (2003) used Q/B=46 y -1 for New Zealand fur seals based on Laws (1984).

94 Ecosystem Modelling of the Chatham Rise

Other information: P/Q, EE, U, accumulation, imports, exports, transfers The fisheries-mediated export of seal biomass from the Chatham Rise study region is negligible for the purposes of the trophic model.

Ecotrophic efficiency of seals is close to zero as most mortality is not due to predation. Instead, dead cetaceans in the model are channelled to carcasses

We assume an unassimilated consumption ratio for fur seals of U=0.2 (Furness, 1984; Lavigne et al. 1982).

Ecosystem Modelling of the Chatham Rise 95

Summary of data

Table C1: Data and parameters for the seal component of the Chatham Rise trophic model

Ind Prop - weight ortion Longevity Biomass P/B Q/B Species Name (kg) Number (%) (y) (tWW) (y -1) (y -1) Arctocephalus forsteri New Zealand fur seal 107.5 40,000 0.064 18.5 274 0.18 18.7 Hooker's sea lion (New Phactarctos hookeri Zealand sea lion) 230 12,200 0.001 20.5 3 0.15 16.2

96 Ecosystem Modelling of the Chatham Rise

References Arnould, J.P.Y.; Boyd, I.L.; J.R. Speakman (1996). Measuring the body composition of Antarctic fur seals (Arctocephalus gazelle): validation of hydrogen isotope dilution. Physiological Zoology 69(1), 93-116.

Baird, S.J. (2011). New Zealand fur seals — summary of current knowledge. New Zealand Aquatic Environment and Biodiversity Report No. 72. 50 p.

Baird, S.J. (2005). Review of observer comments that relate to captures of New Zealand fur seals (Arctocephalus forsteri) during hoki (Macruronus novaezelandiae) trawl fishery operations. NIWA Client Report WLG205-43. (Report prepared for the Hoki Fishery Management Company) 27 p.

Banse, K.; Mosher, S. (1980). Adult body size and annual production / biomass relationships of field populations. Ecol. Monogr. 50, 355-379.

Boren, L.J. (2005). New Zealand fur seals in the Kaikoura region: colony dynamics, maternal investment and health. A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biological Sciences at the University of Canterbury, University of Canterbury. 261 p.

Boren, L. (2010). Diet of New Zealand fur seals (Arctocephalus forsteri): a summary. DOC Research & Development Series 319. Department of Conservation, Wellington. 19 p.

Bradford-Grieve, J.M.; Probert, P.K.; Nodder, S.D.; Thompson, D.; Hall, J.; Hanchet, S.; Boyd, P.; Zeldis, J.; Baker, A.N.; Best, H.A.; Broekhuizen, N.; Childerhouse, S.; Clark, M.; Hadfield, M.; Safi, K.; Wilkinson, I. (2003). Pilot trophic model for Subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology 289: 223-262.

Bradshaw, C.J.A.; Thompson, C. M.; Davis, L.S.; Lalas, C. (1999). Pup density related to terrestrial habitat use by New Zealand fur seals. Canadian Journal of Zoology 77(10): 1579–1586.

Breen PA (2008). Sea lion data for use in the population model for Project IPA200609. Unpublished Final Research Report for Ministry of Fisheries, 30 March 2008. 18 pp. plus Confidential Appendix of 6p.

Breen PA; Hilborn R; Maunder MN; Kim SW (2003). Effects of alternative control rules on the conflict between a fishery and a threatened sea lion (Phocarctos hookeri). Canadian Journal of Fisheries and Aquatic Sciences 60: 527–541.

Breen PA; Kim SW (2006a). Exploring alternative management procedures for controlling bycatch of Hooker’s sea lions in the SQU 6T squid fishery. Unpublished Final Research Report for Ministry of Fisheries Project M0F2002/03L, Objective 3. Revision 5, 3 February 2006. 88 pp.

Ecosystem Modelling of the Chatham Rise 97

Breen PA; Kim SW (2006b). An integrated Bayesian evaluation of Hooker’s sea lion bycatch limits. pp. 471-493 In: A. Trites, S. Atkinson, D. DeMaster, L. Fritz, T. Gelatt, L. Rea, and K. Wynne. (eds.). Sea lions of the world. Alaska Sea Grant College Program, University of Alaska Fairbanks.

Carey, P. W. (1992). Fish prey species of the New Zealand fur seal (Arctocephalus forsteri Lesson). New Zealand Journal of Ecology 16(1): 41-46.

Cawthorn MW (1993). Census and population estimation of Hooker’s sea lion at the Auckland Islands, December 1992–February 1993. DOC Technical Series 2. Wellington, Department of Conservation. 34 pChilderhouse SJ; Dix B; Gales NJ (2001). Diet of New Zealand sea lions (Phocarctos hookeri) at the Auckland Islands. Wildlife Research 28:291–298.

Costa, D.P; LeBoeuf, B.J.; Ortiz, C.I.; Huntley, D.C.A. (1986). Energetics of lactation in the northern elephant seal, Mirounga angustirostris. Journal of Zoology 209: 21–33.

Crawley, M.C.; Wilson, G.J. (1976). The natural history and behaviour of the New Zealand fur seal (Arctocephalus forsteri). Tuatara 22(1): 1–29.

Croxall, J.P. (1987). Seabirds: feeding ecology and role in marine ecosystems. Cambridge University Press, pp 408.

Dickie, G.S.; Dawson, S.M. (2003). Age, growth, and reproduction in New Zealand fur seals. Marine Mammal Science 19(1): 173–185.

Fea, N.I.; Harcourt, R.; Lalas, C. (1999). Seasonal variation in the diet of New Zealand fur seals (Arctocephalus forsteri) at Otago Peninsula, New Zealand. Wildlife Research 26: 147–160.

Furness, W (1984) Modelling relationships among fishers, seabirds and marine mammals. In: Marine Birds: their feeding ecology and commercial fisheries relationships. Ed: Nettleship, D.N.; Sanger, A.; Springer, P.F. Canadian Wildlife Service, Special Publication, Ottawa. 117-126.

Gales NJ (1995). New Zealand (Hooker’s) sea lion recovery plan. Threatened Species Recovery Plan Series 17. Department of Conservation, Wellington.

Gales, N.J. (2009). New Zealand sea lion Phocarctos hookeri. In: Perrin, W.F.; Würsig, B.; Thewissen, J.G.M. Encyclopedia of marine mammals. London, Academic Press. Pp. 763–765.

Gales, N.J.; Fletcher, D.J. (1999). Abundance, distribution and status of the New Zealand sea lion Phocarctos hookeri. Wildlife Research 26: 35-52.

Goldsworthy, S.D.; Shaughnessy, P.D. (1994). Breeding biology and haul-out pattern of the New Zealand fur seal, Arctocephalus forsteri, at Cape Gantheaume, South Australia. Wildlife Research 21: 365–376 .

Harcourt, R.G. (2001). Advances in New Zealand mammalogy 1990–2000: Pinnipeds. Journal of the Royal Society of New Zealand 31(1): 135–160.

98 Ecosystem Modelling of the Chatham Rise

Harcourt, R. G.; Bradshaw, C.J.A.; Dickson, K.; Davis, L.S. (2002). Foraging ecology of a generalist predator, the female New Zealand fur seal. Marine Ecology Progress Series 227: 11–24.

Harcourt, R.G.; Schulman, A.; Davis, L.S.; Trillmich, F (1995). Summer foraging by lactating female New Zealand fur seals (Arctocepbalus forsteri) off Otago Peninsula, New Zealand. Canadian Journal of Zoology 73: 678–690.

Hindell, M.A.; Lea, M.-A. (1998). Heart rate, swimming speed, and estimated oxygen consumption of a free-ranging southern elephant seal. Physiological Journal 71: 74-84.

Irving L. (1970). Morpho-physiological adaptations in marine mammals for life in polar areas. In: M.W. Holdgate (ed.), Antactic Ecology. Vol. 1. Academic Press, London, pp. 455–463.

Jarre-Teichmann, A.; Shannon, L.J.; Moloney, C.L.; Wickens, P.A. (1998). Comparing trophic flows in the southern Benguela to those in other upwelling ecosystems. S. Afr. J. Mar. Sci. 19, 391-414.

Knox, G.A. (2007). Biology of the Southern Ocean. Boca Raton, CRC Press. 2nd edition, 621 pp.

Koopman, H.N. (2007). Phylogenetic, ecological, and ontogenetic factors influencing the biochemical structure of the blubber of odontocetes. Marine Biology 151: 277–291.

Lalas C; Bradshaw CJA (2003). Expectations for population growth at new breeding locations for the vulnerable New Zealand sea lion using a simulation model. Biological Conservation 114:67-78.Ling 2002;

Lasiewski, R.C.; Dawson, W.R. (1967). A re-examination of the relation between standard metabolic rate and body weight in birds. Condor, 69, 13-23.

Lavigne, D.M.; Barchard, W.; Innes, S.; Øritsland, N.A. (1982). Pinniped bioenergetics. FAO Advisory Committee on Marine Resources Research Working Party on Marine Mammals. FAO Fisheries Series (5) Vol. 4: pp. 191- 235.

Lavigne, D.M.; Innes, S.; Worthy, G.A.J.; Kovacs, K.M.; Schmitz, O.J.; Hickie, J.P. (1986). Metabolic rates of seals and whales. Canadian Journal of Zoology 64: 279-284.

Lavigne, D.M.; Barchard, W.; Innes, S.; Øritsland, N.A. (1982). Pinniped bioenergetics. FAO Advisory Committee on Marine Resources Research Working Party on Marine Mammals. FAO Fisheries Series (5) Vol. 4: pp. 191- 235.

Laws, R.M. (1984). Seals In: R.M. Laws (Ed.), Antarctic Ecology. Vol 2. Academic Press, London, pp. 621-715.

Ecosystem Modelling of the Chatham Rise 99

Lockyer, C. (1981). Growth and energy budgets of large baleen whales from the Southern Hemisphere. In: Mammals in the Seas. Vol. III, General Papers and Large Cetaceans. FAO Fisheries Series, pp. 379–487.

Mattlin, R.H. (1978). Population biology, thermoregulation and site preference of the New Zealand fur seal (Arctocephalus forsteri (Lesson, 1828) on the Open Bay Islands, New Zealand. Unpubl. PhD Thesis, Christchurch, University of Canterbury.

Mattlin, R.H. (1987). New Zealand fur seal, Arctocephalus forsteri, within the New Zealand region. In Croxall, J.P.; Gentry, R.L. Status, biology, and ecology of fur seals: Proceedings of an international symposium and workshop, Cambridge, England, 23–27 April 1984. NOAA Technical Report NMFS-51.

Mattlin, R.H.; Gales N.J.; Costa, D.P. (1998). Seasonal dive behaviour of lactating New Zealand fur seals (Arctocephalus forsteri). Canadian Journal of Zoology 76(2): 350–360.

Meynier, L., (2010). New Zealand sea lion bio-energetic modelling, Unpublished Final Report for Project IPA2009-09. Presented to AEWG May 17 2011, Wellington, New Zealand, 34 p.

Ministry for Primary Industries (2012). Aquatic Environment and Biodiversity Annual Review 2012. Compiled by the Fisheries Management Science Team, Ministry for Primary Industries, Wellington, New Zealand. 387 p.

Nagy, K.A. (1987). Field metabolic rate and food requirement scaling in mammals and birds. Ecol. Monogr. 57, 111-128.

Nordoy, E.S.; P.-E. Martensson; A.R. Lager; L.P. Folkow; A.S. Blix (1995). Food consumption of the northeast Atlantic stock of harp seals. Procs. Biology of Marine Mammals, Tromso, Norway, 29 Nov-1 Dec 1994, Elsevier Science, Amsterdam (Netherlands).

Richards, R. (1994). "The upland seal" of the Antipodes and Macquarie Islands: a historian's perspective. Journal of The Royal Society of New Zealand 24:289- 295.

Riedman, M. (1990). Pinnipeds: Seals, Sea Lions, and Walruses. University Of California Press: Berkeley, pp 1–149.

Rowe, S.J. (2009). Conservation Services Programme observer report: 1 July 2004 to 30 June 2007. DOC Marine Conservation Services Series 1. Department of Conservation, Wellington. 93 p.

Schneider, D.; Hunt, G.L. (1982). Carbon flux to seabirds in waters with different mixing regimes in the southeastern Bering Sea. Marine Biology, 67, 337-344.

Shirihai, H. (2008). The Complete Guide to Antarctic Wildlife, Second Edition. Princeton University Press, pp 544.

100 Ecosystem Modelling of the Chatham Rise

Taylor, R.H. (1990). Records of subantarctic fur seals in New Zealand (Note). New Zealand Journal of Marine and Freshwater Research 24: 499–502.

van Franeker, J.A.; Bathmann, U.V.; Mathot, S. (1997). Carbon fluxes to Antarctic top predators. Deep Sea Research II 44(1/2): 435-455.

Vinogradov, A.P. (1953). The elementary chemical composition of marine organisms. Memoir of the Sears Foundation for Marine Research, Yale University, New Haven II, 647 pp.

Wilson, G. J. (1981). Distribution and abundance of the New Zealand fur seal, Arctocephalus forsteri. Fisheries Research Division Occasional Publication No. 20. 39 p.

Ecosystem Modelling of the Chatham Rise 101

Appendix D Fish

Introduction This section concerns all fish on the Chatham Rise except small, mesopelagic fishes (mainly myctophids) that are considered in Appendix E. There are more than 200 species of fish known to occur on the Chatham (based on Chatham Rise annual trawl survey), most of which are demersal (bottom-associated). Information on the basic ecology and trophic role of many of these species is limited. For the estimation of parameters for the trophic model of the Chatham Rise, we gather data on all fish as individual species. These data include estimates of mean individual size, numerical abundance, biomass, energetics (growth, consumption, growth efficiency), diet, predators, and fishery removals. The quality and quantity of information available to estimate these parameters is very variable. New Zealand commercial fisheries are predominantly managed by a Quota Management System (QMS). There tends to be better information on fish (or fish stocks) that are commercially harvested and managed under the QMS. Where data is not available for fishes, we try and use information on the better known species to estimate parameters for the more poorly known species of fish.

Most information on fishes on the Chatham Rise concerns individuals that are of a size to be available to commercial fisheries (greater than about 20 cm total length). These are henceforth referred to as “adult” fish. Small fish which have not recruited into the fisheries and which are not normally caught by commercial fisheries are termed “juvenile” for the purposes of this study. According to this definition, the “juvenile” fish category includes small sexually mature fish which are not commonly taken by the fisheries.

Grouping of fish species There are too many species of fish, and too poor information on most, to be able to consider each species separately. Instead, fishes were combined into trophic groups (or synonymously “trophic compartments”) in the model. The aim of this grouping of fishes was to have a reasonably small number of groups where the biota in a given group had a “similar” set of energetic parameters and trophic roles, and yet where there was enough information on each group to drive the modelling. Factors defining “trophic roles” include prey, predators and life history strategy (including, for example, position in the water column, presence/absence of diel migration). A number of alternative ways to group fishes in mass- balance models have been used (Table D1). None of these methods of grouping fishes into trophic groups is completely objective or ideal.

In this study, we grouped fish into 4 species/species groups (hoki, orange roughy, oreos, warehous), 5 trophic guilds (see below: large javelinfish guild, small javelinfish guild, hake guild, rattails & ghost shark guild, and ling guild), a cryptic group of fishes (called “small demersal fishes” – see below for details) and mesopelagic fish (considered in Appendix E).

102 Ecosystem Modelling of the Chatham Rise

Table D1: Methods of grouping fishes in mass-balance models.

Method Example Pros Cons Single species • Snapper Information and Too many species and too • Red cod management is usually by limited information on rarer species species to be feasible for all fishes Taxonomic • Triplefins Taxonomic similarity often Taxonomically-similar species groups • Skates and rays implies similarity of size can have and/or similar ecosystem very different sizes and role ecosystem roles Size-based • Small fishes Energetics and potential Often some degree of niche • Medium-sized fishes prey are closely linked to separation between fishes of • Large fishes size similar size Lifestyle • Demersal Trophic role is often linked Different sizes of fish with the • Benthopelagic to lifestyle same lifestyle can have very • Mesopelagic different energetics Habitat / • Reef fish Prey and predators often Can be high degree of niche location • Estuarine fish related to habitat and separation within given • Open water fish location habitat / location Predominant • Piscivores Aligned with model that is Most fishes will have a diet prey • Planktivores driven by predator-prey that varies with season and • Invertebrate feeders connections age; diet is often poorly • Scavengers known.

Chatham Fish Guilds A total of 8800 stomach samples were analysed from 25 fish species caught by research trawl surveys on Chatham Rise to the east of New Zealand between 2004 and 2007. These species represent the majority of fish biomass on the Chatham Rise. Diet compositions were described using percentage wet weight of prey and trophic guilds were identified from cluster analysis (Dunn et al. submitted). Fishes not included in the guild analysis were partitioned into guilds according to similarity of diet or, if not known, according to morphology and ecological information suggesting a type of feeding behaviour. Guild structure from the analysis of fish diets on the Chatham Rise is given in Table D2 and shown in Figure D1.

The 9 guilds fell into four broad feeding groups (demersal foragers, benthopelagic foragers, pelagic foragers, salp specialists) – see Tables D3 and D4. Guilds 6–8 were demersal foragers, concentrating on fishes (primarily rattails, and sometimes fishing discards), benthic crustaceans, and other benthic invertebrates. Guilds 2, 3, 5, and 9 were benthopelagic foragers specialising either in small crustaceans (the first two guilds) or fish and cephalopods. Guild 4 was primarily pelagic foragers concentrating on fish and shrimps. Guild 1 comprised salp specialists. The groups used in the model follow this guild structure, except that hoki are treated as a separate trophic group. Species was found to be more important to size in terms of feeding guild (Dunn et al. submitted); javelinfish and hake were the only species other than hoki that were split between guilds. We define 9 fish groups for the purpose of the trophic model (Table D3). These include hoki, orange roughy and oreos (black, smooth, spiky) as separate groups, and 6 groups made from the 9 trophic guilds in Dunn et al. (submitted). Javelinfish was the only species that mapped onto two different trophic groups, and we partitioned biomass and diet evenly between these groups. We allocated other species to one of these 9 trophic groups on the basis of information on diet from New Zealand if available or from Fishbase otherwise. These other species provided

Ecosystem Modelling of the Chatham Rise 103

less than 4% to the total biomass so these diets are unlikely to be important to the modelling results.

Small demersal fishes A number of fish species are sampled poorly by both commercial and research bottom trawling gear. These include pelagic species (e.g. saury, Scomberesox saurus ; barracudinas, Paralepididae ; rotund cardinalfish, Rosenblattia robusta ; messmate fish Echiodon cryomargarites ), fish that live very close the seabed and are likely to be passed over by bottom trawls (e.g. flatfish, slickheads), and small/slender demersal fishes that can pass through the meshes of trawl gear. Commercial fishing gear tends to use a mesh size of 100 mm and research trawls use a cod-end mesh size of 60 mm. Slender fish or fish smaller than about 20 cm are not likely to be retained. Many such species are commonly found in the stomachs of commercially-important deepwater fish (Dunn et al., 2009) and are also caught using the NIWA “ratcatcher” bottom trawl (Doonan et al., 2006). The NIWA full wing trawl ("ratcatcher") has upper and lower wings, with a wingspread of about 25 m, a door spread of about 115 m, a headline height of about 3.3 m, 6 inch mesh in the wings, 40 mm mesh (full inside mesh) codend, and low (200 mm bobbins) ground gear. This net has small meshes and small ground gear (closer bottom contact) than the standard bottom trawl, so that smaller fish are more likely to be retained. Data from the ratcatcher trawl on voyage TAN0408 on the Chatham Rise showed the presence of a number of species of small rattails, eels, chimaeras and slickheads. In the trophic model, this group of cryptic fish is called “small demersal fish” because bottom-associated specie are likely to dominate the biomass though pelagic and bentho-pelagic species are included.

104 Ecosystem Modelling of the Chatham Rise

Table D2: Predator species, predator group definitions, numbers of non-empty stomachs (N) (Dunn et al., submitted, Table 1. Squid excluded). Total number of prey categories recorded (P), the Shannon-Wiener diet breadth index (H), and the reference to the detailed diet analysis. Length range values are rounded to the nearest whole cm; TL, total length; PL, snout to end of pelvic fin; CL, snout to end of upper caudal fin; FL, fork length.

Scientific name Common name Group code Group definitions Length N P H Reference Guild range

Deania calcea Shovelnose SNDall All fish 38–110 TL 215 Dunn et al. in prep. 5 dogfish 12 1.94 Squalus acanthias Southern spiny SPDsml Weight < 1890 g 55–79 TL 242 20 1.70 Dunn et al. in prep. 9 dogfish SPDlge Weight ≥ 1890 g 72–106 TL 241 26 1.72 9 Dipturus innominatus Smooth skate SSKsml Length < 75 cm 29–74 PL 33 16 1.53 Forman & Dunn 2012 8 SSKlge Length ≥ 75 cm 75–152 PL 86 17 1.80 8 Hydrolagus bemisi Pale ghost shark GSPtlo Bottom temperature < 7.5 ° C 27–84 CL 54 17 1.86 Dunn et al. 2010a 6 GSPthi Bottom temperature ≥ 7.5 ° C 34–88 CL 37 17 1.30 6 Hydrolagus Dark ghost shark GSHbnk STF = bank 33–73 CL 62 8 1.12 Dunn et al. 2010a 6 novaezealandiae GSHcre STF = crest 31–71 CL 66 9 0.93 6 Harriotta raleighana Longnosed LCHall All fish 29–92 CL 95 Dunn et al. 2010a 6 chimaera 15 1.36 Psuedophycis bachus Red cod RCOwst Longitude < 177 ° E 22–68 TL 141 20 1.90 Horn et al. (2012) 8 RCOest Longitude ≥ 177 ° E 19–67 TL 94 20 1.36 8 Macruronus Hoki HOKbnksml STF = bank, length < 50 cm 38–50 TL 79 7 1.55 Connell et al. 2010 4 novaezelandiae HOKbnkmed STF = bank, length ≥ 50 cm 50–82 TL 115 10 1.77 5 HOKothsml STF ≠ bank, length < 50 cm 36–49 TL 46 7 1.26 4 HOKothmed STF ≠ bank, length 50–83 cm 50–83 TL 778 19 1.50 4 HOKothlge STF ≠ bank, length > 83 cm 83–114 TL 267 15 1.51 5 Merluccius australis Hake HAKsml Length < 62 cm 38–62 TL 183 16 1.50 Dunn et al. 2010b 5 HAKlge Length ≥ 62 cm 62–133 TL 311 19 1.56 9 Caelorinchus Oblique banded CASsml Weight < 120 g 17–33 TL 70 13 1.66 Stevens & Dunn 2011 6 aspercephalus rattail CASmed Weight 120–215 g 28–37 TL 76 19 2.02 6 CASlge Weight > 215 g 33–44 TL 63 19 1.57 6 Caelorinchus bollonsi Bollons’ rattail CBOsml Weight < 720 g 27–52 TL 217 16 1.34 Stevens & Dunn 2011 6 CBOlge Weight ≥ 720 g 46–62 TL 103 15 1.27 6

Ecosystem Modelling of the Chatham Rise 105

Caelorinchus Oliver’s rattail COLnth Latitude < 43.09 ° S 17–35 TL 41 9 1.24 Stevens & Dunn 2011 2 oliverianus COLcen Latitude 43.09–43.90 ° S 15–39 TL 79 11 1.88 2 COLsth Latitude > 43.90 ° S 20–38 TL 44 9 1.11 2 Lepidorhynchus Javelinfish JAVsml Weight < 115 g 17–39 TL 127 13 1.69 Stevens & Dunn 2011 2 denticulatus JAVmed Weight 115–255 g 30–50 TL 115 13 1.43 4 JAVlge Weight > 255 g 42–63 TL 113 14 0.69 4 Genypterus blacodes Ling LINshlsml Depth < 428 m, length < 59 cm 33–59 TL 138 14 1.44 Dunn et al. 2010b 8 LINshlmed Depth < 428 m, length 59– 59–83 TL 196 8 83 cm 16 1.40 LINshllge Depth < 428 m, length > 83 cm 83–153 TL 226 19 2.15 8 LINdepsml Depth ≥ 428 m, length < 59 cm 34–59 TL 101 14 1.61 8 LINdepmed Depth ≥ 428 m, length 59– 59–83 TL 211 8 83 cm 17 1.55 LINdeplge Depth ≥ 428 m, length > 83 cm 83–163 TL 326 27 1.99 8 Beryx splendens Alfonsino BYSsml Weight < 425 g 17–27 FL 128 8 1.38 Horn et al. 2010 4 BYSlge Weight ≥ 425 g 26–47 FL 121 11 0.87 4 Cyttus traverse Lookdown dory LDOshl Depth < 370 m 13–51 TL 98 10 1.22 Forman & Dunn 2010 7 LDOmid Depth 370–540 m 14–54 TL 251 16 1.33 7 LDOdep Depth > 540 m 21–56 TL 107 12 0.89 7 Centriscops Banded BBEall All fish 14–28 TL 80 Dunn et al. 2009 2 humerosus bellowsfish 16 2.17 Helicolenus percoides Sea perch SPEnth Latitude < 43.4 ° S 15–48 TL 196 19 1.72 Horn et al. (2012) 8 SPEsth Latitude ≥ 43.4 ° S 12–50 TL 218 22 2.05 8 Lepidoperca aurantia Orange perch OPEall All fish 16–37 FL 240 11 0.56 Horn et al. (in prep.) 3 Brama australis Southern Ray’s SRBsml Weight < 1440 g 36–46 FL 193 12 2.06 Horn et al. (in prep.) 4 bream SRBlge Weight ≥ 1440 g 42–52 FL 199 9 1.46 4 Kathetostoma Giant stargazer STAall All fish 23–80 TL 467 Dunn et al. 2009 9 giganteum 23 2.19 Thyrsites atun Barracouta BARall All fish 47–85 FL 80 11 1.42 Dunn et al. 2009 9 Seriolella caerulea White warehou WWAall All fish 17–62 FL 301 14 0.26 Horn et al. 2011 1 Seriolella punctata Silver warehou SWAall All fish 23–57 FL 485 14 0.15 Horn et al. 2011 1

106 Ecosystem Modelling of the Chatham Rise

Table D3: Trophic groups used in the Chatham Rise model and corresponding description of guild diet and feeding (Dunn et al., submitted).

Guild(s) Guild name Species Description Trophic Trophic groups for ID Chatham Rise model 1 Salp specialists White warehou Feeding almost exclusively on salps (97% by weight), 4 Warehou Silver warehou with jellyfish and amphipods the next most important dietary items. The diet breaths of these species were markedly lower than for any other predator (0.15–0.26). 2 Benthopelagic foragers Banded bellowsfish Feeding on wide range of crustaceans, but mainly 5 Small javelinfish (crustaceans) Oliver’s rattail copepods, shrimps and amphipods. Diet breadth guild Javelinfish (small) ranged from low to high in this guild (1.11–2.17). [benthopelagic invertebrate feeders] 3 Benthopelagic foragers Orange perch Fed almost exclusively on euphausiids, and had a very 5 Small javelinfish (krill) low diet breadth (0.56). guild [benthopelagic invertebrate feeders] 4 Pelagic foragers Hoki (small-medium) Fish and shrimps dominated the diet in this group. The 6 Large javelinfish Alfonsino numbers of prey categories consumed by members of guild Ray’s bream this guild were generally low, and diet breadth indices [pelagic foragers] Javelinfish (med, large) generally low to medium (0.69–1.55). 5 Benthopelagic foragers Hoki (large) Small fish (both demersal rattails and small pelagic 7 Hake_guild (fish & squid) Hake (small) species), with significant cephalopod component. [benthopelagic Shovelnose dogfish Medium to high diet breadths (1.50–1.94). predators] 6 Benthic foragers (fish & Dark ghost sharks Some diets strongly dominated by crabs, but with a 8 Rattails & ghost small invertebrates) Pale ghost sharks significant echinoid component; others more sharks Longnosed chimaeras generalised benthic invertebrate diet comprising worms, [benthic invertebrate Oblique banded rattail crabs, galatheids, and shelled molluscs. Diet breadths feeders] Bollons’ rattail ranged from low to high (0.93–2.02). This guild also ate salps. 7 Benthic foragers (rattails & Lookdown dory Feeding almost exclusively on rattails and shrimps. Low 9 Ling guild shrimps) diet breadths (0.89–1.33). [benthic predators] 8 Benthic foragers (fish & Smooth skates Benthic foraging for fish and crustaceans, including 9 Ling guild large crustaceans) Ling fishing discards. Feeding on relatively broad range of [benthic predators] Red cod demersal fishes. Crustaceans generally medium-large Sea perch (scampi, galatheids, crabs, large shrimps), Diet breadths also medium to high (1.36–2.15). 9 Benthopelagic foragers Giant stargazer Feeding mainly on cephalopods and benthopelagic 7 Hake_guild (squid) Southern spiny dogfish fishes, but also commercial fishing discards. High diet [benthopelagic Barracouta breadths (1.42–2.19). predators] Hake (large)

Ecosystem Modelling of the Chatham Rise 107

4, 5 Hoki Small/medium hoki: fish was the dominant dietary 1 Hoki component Medium to large hoki: dominated by small fish (both demersal rattails and small pelagic species), but also comprised a significant cephalopod component. Orange roughy Orange roughy 2 Orange roughy Oreos Black oreo 3 Oreos Spiky oreo Smooth oreo

108 Ecosystem Modelling of the Chatham Rise

Table D4: The most abundant prey categories accounting for at least 90% of the diet of each of the 9 guilds, expressed as average percentage prey weight across predator categories, and the median diet breadth for each guild (from Dunn et al. submitted, Table 3).

Guild Prey category 1 2 3 4 5 6 7 8 9

Salps 96.6 – – – – 3.8 – – – Shelled molluscs – – – – – 7.8 – – – Cephalopods – – – – 13.8 – – 3.4 21.8 Marine worms – – – – – 17.7 – – – Scampi – – – – – – – 13.6 – Galatheids – – – – – 13.7 – 22.9 – Natant decapods – 23.9 – 34 4 3 32.2 3.3 – Decapod crabs – – – – – 34.6 – 8.9 – Euphausiids – 5.5 86.9 8 – 5.1 – – 5 Amphipods – 12.3 – 2.9 – – – – – Isopods – 6.1 – ––––– – Copepods – 31.5 – ––––– – Other crustaceans – 7.5 – ––––– – Starfish & sea urchins – – – – – 6.7 – – – Sharks – – – ––––– 2.3 Other marine eels – – – – – – – 2 – Deep-sea smelts – – – – – – 4.4 – 3.8 Lightfish & dragonfish – – 6.7 16.1 24.8 – – – – Lanternfish – 3.8 – 29.9 10.2 – – – – Morid cods – – – ––––– 3.3 Hakes – – – – 4.3 – – 2.5 20.7 Rattails – – – – 28.2 – 54.2 13.7 19.6 Ling – – – ––––– – Dories & oreos – – – – 7.3 – – – – Scorpionfish & flatheads – – – – – – – 2.2 – Perch-like fish – – – – – – – 1.9 3.8 Commercial discards – – – – – – – 16.4 9.8

Median diet breadth 0.2 1.69 0.56 1.44 1.51 1.35 1.22 1.67 1.7

Ecosystem Modelling of the Chatham Rise 109

Figure D1: Dendrogram of group-averaged cluster analysis of square root transformed Bray- Curtis dissimilarities based on %W. Solid black lines indicate significant nodes from SIMPROF tests. (Dunn et al. submitted, Figure 2). The 9 guilds are shown in red, numbered from 1 at the bottom to guild 10 at the top. Note that “NOS” are arrow squid and not used here.

110 Ecosystem Modelling of the Chatham Rise

Biomass

The main commercial fisheries of the Chatham Rise are hoki ( Macruronus novaezelandiae , 57%), orange roughy ( Hoplostethus atlanticus ) and oreos ( Pseudocyttus maculatus, Allocyttus niger, Neocyttus rhomboidalis ). Many species of non-QMS deepwater sharks commonly occur in the study region, including dogfish and rattails (Macrouridae). Other abundant species caught on the Chatham Rise include javelinfish ( Lepidorhynchus denticulatus ) and six species of slickhead.

Five methods were used to estimate biomass of fish on the Chatham Rise:

Tier 1 : Where current biomass of Chatham Rise fish stocks were estimated as part of the QMS process using deterministic stock assessment analyses (Ministry of Fisheries 2012), we used these to estimate biomass on the Chatham Rise taking into account the spatial distribution of the stock. We used data from stock models given in the 2009 plenary report (Ministry of Fisheries 2009) to estimate biomass of hoki, black oreo, ling, hake, smooth skate and rough skate. No consensus of stock size for orange roughy on the Chatham Rise is available.

Tier 2 : The biomass of the 50 species with highest catch rates on the Chatham Rise trawl survey were estimated by scaling the recent trawl surveys of the Chatham Rise (average of strata 1–20 in period 1992–2007: Tuck et al. 2009), using the relationship shown in Figure D2. This estimate of biomass was accepted if the annual commercial catch (see below for how this as estimated) was greater than 0.5 of the annual production of the species.

Tier 3 : Biomass was estimated such that the annual commercial catch in the Chatham Rise region (see below for how this as estimated)was 0.5 of the annual production of the species.

Small demersal fishes : As the biomass of cryptic fish is not known on the Chatham Rise, we estimated their biomass as that required to provide an annual production equal to the modelled consumption by other predators in the system.

Mesopelagic fish : Biomass of small mesopelagic fishes over the Chatham Rise were estimated based on acoustic data as explained in Appendix E.

Where it is known that fish migrate into and out of the study area at different times of the year (e.g. hoki), biomass, production and consumption values for the fish have been reduced according to the pro rata time estimated to be spent in the study area. Final estimates of biomass and other parameters are gin in Table D5.

Wet-weight (WW) biomass values were converted to gC m -2 assuming that carbon in fishes is 10% wet weight. The ratio of carbon to wet weight of fish between 5.3% and 12.5% (mean 8.3%) based on values from Ikeda (1996), Parsons et al. (1984), McLusky (1981) and Cohen & Grosslein (1987).

Ecosystem Modelling of the Chatham Rise 111

Figure D2: Relation between total biomass from stock models and Chatham Rise trawl survey biomass for hoki, black oreo, ling, hake, smooth and rough skates.

Production Production by fishes in the model was estimated using the allometric equations of Banse & Mosher (1980). The equations lead to annual P/B values between 0.23 y-1 and 1.0 y -1 which seems reasonable for middle-depth species though may overestimate production rates of some deep water species which have anomalously low natural mortality and production rates. We hence reduced the estimated production rate of Banse & Mosher (1980) by applying a factor of 0.5 for orange-roughy (P/B=0.25 y -1), and 0.7 for oreo (P/B=0.33-0.38 y - 1). In other work, P/B for orange roughy was estimated as a comparable 0.15 y -1 (Pankhurst & Conroy 1987). For demersal fishes on the Southern Plateau, New Zealand, Bradford- Grieve et al. (2003) gave P/B=0.40 y -1 compared to our mean value of 0.30=0.42 y-1.

112 Ecosystem Modelling of the Chatham Rise

Consumption The consumption of prey required for maintenance and growth of fish depends on their size, type and life strategy, as well as their physical environment. Palomares & Pauly (1998) derived an empirical multivariate relationship to predict food consumption (Q/B) of fish populations from total mortality, food type, fish morphometrics (based on tail shape), and temperature. Here, we assumed all fish to be carnivorous. Tail shape was taken from photographs of adult fish. Temperature was estimated from the average depth of fish occurrence on the Chatham Rise (Anderson et al. 1998), and the depth-temperature relationship for the Chatham Rise. The bottom water temperature estimated based on the mean depth of the fish was 6.9°C on average. Maximum fish weights were taken from Ministry of Fisheries (2009), supplemented by data from FishBase (2000). Where data was missing, or for eel-like fish (e.g. hoki, rattails, ling) where the Palomares & Pauly (1998) relationship does not hold, we estimated Q/B from maximum fish lengths and Q/B values derived from other Chatham Rise species. We hence estimate a consumption rate (Q/B) for demersal fish on the Chatham Rise of between Q/B=1.5 y-1 and Q/B=5.4 y-1. Our mean Q/B was 2.8 y -1. For comparison, Bradford-Grieve et al. (2003) gave Q/B=2.6 y-1 for demersal fishes.

These values imply a mean growth efficiency for all demersal fishes on the Chatham Rise of P/Q=0.15 (range 0.11–0.24), similar to Bradford-Grieve et al. (2003) which gave P/Q=0.12 for demersal fishes over the New Zealand Southern Plateau.

Fishery and Export Export of fish in the model has three components: commercial and recreational fish catch, net migration of fish from the study area, and transfer of fish from the “juvenile/young” compartment to the “adult” compartment due to growth over the year. Recreational fish catch is negligible. Commercial catches of QMS species were derived from QMS reported catches in the 2009 Ministry of Fisheries plenary (Ministry of Fisheries 2009), from the fishing years 2003/2004 to 2007/2008. Values given by statistical area are used to estimate catches from the Chatham Rise study region using information on the distribution of fishing and species. We assume that all catches are reported. For non-QMS species, we used data on fishery catches of all major species from fisheries observers on the Chatham Rise (Livingston et al. 2003) reconciled to reported catches (Figure D3). Where these estimated catch rates led to the proportion of the total annual production of a species taken as catch to be unrealistically high (>0.5) and the biomass was estimated based on the scaled trawl survey biomass, we increased our estimation of biomass so that exactly 0.5 of the annual production was taken was catch. For species that had no observed catch, we estimated catch rates such that 0.2 of the annual production of the species was taken as catch.

Quantitative estimates of net biomass export due to migration are scarce, and we make the assumption that the net annual migration of fish from Chatham Rise stocks is small. Transfer of juvenile and young fish into the adult fish compartment may be estimated using weight- growth rate-frequency data, but was assumed to be small in the current version of the model.

Ecosystem Modelling of the Chatham Rise 113

Figure D3: elation between total catches reported to QMS and observed catches (Livingston et al. 2003).

Long-term trends in biomass Research suggests that the abundances of some fish on the Chatham Rise have shown a trend over the last 10 years (Livingston et al. 2003; O’Driscoll pers. com.). As accumulation rates were often variable between years, equivocal, or small (as a proportion of annual production), we assumed no trends in abundance in this model.

Diet Information on diets for fish on the Chatham Rise primarily based on results of the Ministry of Fisheries project ZBD200402 (Stomach analysis of middle-depth fish species of the Chatham Rise) as given in Dunn et al. (2009), and papers resulting from this project (e.g. Dunn et al. 2010a, b; Connell et al. 2010; Stevens & Dunn 2010), including the guild analysis described earlier (Dunn et al. submitted). In addition, information from the primary literature was used. In New Zealand, there have been over 20–30 years of research surveys and extensive examination of stomach contents of fish species (e.g. Clark 1985; Clark et al. 1989; Rosecchi et al. 1988). The data from more than 27 scientific papers on fish diets around New Zealand has recently been summarized by Stevens et al. (2007). Much of this work provides only limited qualitative information on diet composition, usually in terms of presence/absence on material in the fish stomachs, and there are few studies assessing how much energy intake of fish is from different sources. Also, only few of the studies have looked specifically at continental slope areas near to the study region. Clark (1985) found that hoki south of the study area were essentially plankton (water column) feeders, feeding mainly on natant decapods, amphipods and mesopelagic fish. Work by Bulman & Blaber (1986) shows that the proportion of energy obtained by hoki from mesopelagic fish can vary between 20 and 70%, depending on location and hoki size. Oreo (both black and smooth) in the study area were found to be predominantly plankton feeders, taking salps, in addition to natant decapods, and amphipods (Clark et al. 1989). The same study showed some species of

114 Ecosystem Modelling of the Chatham Rise

rattails ( Macrouridae ) to feed predominantly on benthic invertebrates. Tarakihi (Nemadactylus macropterus ) is also a predominant benthic feeder (Probert 1986 and references therein). For other species, benthic invertebrates may be an important part of their diet, for example spiny dogfish ( Squalus spp. ), and common warehou ( Serioletta brama ). Diets were weighted according to the total consumption of food by that species, based on biomass and Q/B values estimated as above. The fact that diets of fish change considerably with fish size, location, and probably with food availability means that diet figures should always be considered approximate. We note however that Horn & Dunn (2010) showed substantial similarities in diet of hoki, hake and ling on the Chatham Rise over 3 recent years. Diet of small demersal fishes is not well known, though the diets of some small species of rattails from the Chatham Rise have been recently studied by examination of stomach contents (Stevens et al., in prep). This work found that three species were predominantly benthic foragers ( Coelorinchus parvifasciatus on small epifaunal crustaceans, C. biclinozonalis on epifaunal decapods, and Coryphaenoides dossenus on small benthic fish and epifaunal decapods) and three species were predominantly benthopelagic foragers ( C. fasciatus on gammarid and hyperiid amphipods and calanoid copepods, C. matamua on epifaunal decapods and calanoid copepods, and Lucigadus nigromaculatus on gammarid amphipods and suprabenthic mysids).

Discarded Fish Discarded fish include both target and non-target species that are returned to the sea as a result of economic, legal or personal considerations (Anderson et al. 2000). In the model, we returned the proportion discarded to the carcass group. The percentage of the catch that was estimated to be retained ranged from >95% for major commercial species (hoki, orange roughy, oreos, ling, silver warehou, hake, arrow squid), through 35% (rattails), 17% (dogfish), to <15% for bycatch species (slickheads, chimaera). For all species together, approximately 11% of fish-catch is discarded for the Chatham Rise as a whole. At a sinking rate of 10 cm/s, material will take less than 11 hours to reach the sea-bed of the Chatham Rise, so bacterial action on the material in the water column will be negligible. We hypothesise that only a small proportion of discarded material will reach the sea-bed, and that the majority will be consumed by carnivores as it sinks.

Other information: EE, U Unassimilated consumption factors are not known for fishes in the study region and were assumed to be U=0.27 for all fish groups in the model as for carnivorous fish (Brett & Groves 1979). Ecotrophic efficiencies (EE) are not known for fishes. Ecotrophic efficiency measures the proportion of the annual production that is available for predation (“passed up the food chain”) as well as exported (including as fish landings, migration, spawning output, growth transfer to another trophic group) or accumulated. The remainder of the production (a fraction of 1-EE) is transferred to a detrital group. In the case of fish, dead fish or parts of fish are likely to be scavenged rather than decomposed by bacterial action and so will be passed in the model to the carcass group. This material is from two sources: (1) fish that die from causes other than direct predation, including starvation, disease, excessive parasite loading etc; (2) fishery catch that is discarded at sea either as whole fish (assumed dead) or as parts of fish due to processing at sea (e.g. heads, offal). It is likely that the vast majority of fish

Ecosystem Modelling of the Chatham Rise 115

natural mortality is likely to be due to direct predation rather than other causes. The proportion of annual production leading to dead fish due to causes other than direct predation and fishing is not known but is assumed to be 1%. The amount of biomass discarded was estimated as described earlier (Table D5).

116 Ecosystem Modelling of the Chatham Rise

Summary of parameters

Table D5: Summary of parameters for the fish groups used in the Chatham Rise model. 1See Table D3 for explanation of trophic groups. See text for explanation of the different methods of estimating biomass (tiers 1–3). Trophic Biomass B P/B Q/B Catch Group Code Species group 1 method tWW y-1 y-1 P/Q tWW y -1 Discard rate Hoki HOK Macruronus novaezelandiae 1 tier 1 194637.8 0.42 2.65 0.16 32174.08 0.10 Black oreo BOE Allocyttus niger 3 tier 1 97100.0 0.38 2.22 0.23 1853.78 0.10 Javelinfish JAV Lepidorhynchus denticulatus 6 tier 2 30278.2 0.37 2.54 0.14 2076.55 0.90 Bollons rattail CBO Caelorinchus bollonsi 8 tier 2 24028.3 0.62 3.94 0.15 2960.38 0.65 Ghost shark GSH Hydrolagus novaezealandiae 8 tier 2 18461.2 0.36 2.30 0.15 1320.08 0.83 Ling LIN Genypterus blacodes 9 tier 1 70228.4 0.29 1.96 0.14 4433.20 0.10 Silver warehou SWA Seriolella punctata 4 tier 3 33348.9 0.44 3.66 0.11 7254.24 0.10 Lookdown dory LDO Cyttus traversi 9 tier 2 12764.2 0.38 2.08 0.17 231.13 0.10 Spiny dogfish SPD Squalus acanthias 7 tier 3 21337.4 0.35 2.39 0.14 3714.34 0.83 Spiky oreo SOR Neocyttus rhomboidalis 3 tier 2 9916.5 0.34 1.88 0.24 199.62 0.10 Alfonsino BYS Beryx splendens 6 tier 2 9507.4 0.41 2.85 0.13 645.54 0.10 Pale ghost shark GSP Hydrolagus bemisi 8 tier 2 7221.1 0.33 2.01 0.15 600.36 0.83 Sea perch SPE Helicolenus spp. 9 tier 2 6834.4 0.55 2.90 0.18 1203.87 0.10 Shovelnose spiny dogfish SND Deania calcea 7 tier 3 6100.4 0.30 1.95 0.14 911.43 0.83 White warehou WWA Seriolella caerulea 4 tier 3 4394.8 0.36 3.00 0.11 788.22 0.10 Common roughy RHY Paratrachichthys trailli 8 tier 2 3424.9 0.63 4.04 0.15 432.89 0.50 Hake HAK Merluccius australis 7 tier 1 15918.3 0.33 1.94 0.16 2635.00 0.10 Giant stargazer STA Kathetostoma giganteum 7 tier 3 3244.0 0.37 2.28 0.15 594.71 0.10 Olivers rattail COL Caelorinchus oliverianus 5 tier 2 1454.9 0.52 3.33 0.15 150.21 0.65 Smooth oreo SSO Pseudocyttus maculatus 3 tier 3 44455.5 0.33 1.90 0.23 7414.27 0.10 Smooth skate SSK Dipturus innominatus 9 tier 1 1314.4 0.40 2.47 0.15 264.25 0.10 Silver dory SDO Cyttus novaezealandiae 6 tier 2 1055.1 0.48 3.11 0.14 101.56 0.10 Baxters dogfish ETB Etmopterus baxteri 7 tier 3 3574.4 0.28 1.79 0.15 509.11 0.83 Oblique banded rattail CAS Caelorinchus aspercephalus 8 tier 2 910.8 0.52 3.33 0.15 94.04 0.65 Orange perch OPE Lepidoperca aurantia 5 tier 2 814.8 1.00 5.41 0.17 163.49 0.10 Barracouta BAR Thyrsites atun 7 tier 3 24404.1 0.40 2.67 0.14 4886.46 0.10 Banded bellowsfish BBE Centriscops humerosus 5 tier 2 662.9 0.56 3.60 0.15 74.21 0.83

Ecosystem Modelling of the Chatham Rise 117

Long -nosed chimaera LCH Harriotta raleighana 8 tier 2 600.6 0.30 2.20 0.13 35.44 0.90 Long-nosed velvet dogfish CYP Centroscymnus crepidater 7 tier 2 486.8 0.26 1.72 0.14 25.23 0.83 Red cod RCO Pseudophycis bachus 9 tier 2 450.8 0.36 2.35 0.14 32.68 0.10 Rudderfish RUD Centrolophus niger 6 tier 2 319.1 0.64 4.11 0.15 41.07 0.50 Leafscale gulper shark CSQ Centrophorus squamosus 6 tier 2 257.5 0.23 1.53 0.14 11.81 0.83 Ribaldo RIB Mora moro 8 tier 3 2004.8 0.40 2.43 0.15 402.98 0.10 Jack mackerel JMM Trachurus murphyi 5 tier 3 696.8 0.63 4.23 0.14 218.14 0.10 School shark SCH Galeorhinus galeus 8 tier 3 3693.5 0.27 2.01 0.13 496.54 0.10 Swollenhead conger SCO Bassanago bulbiceps 9 tier 2 108.6 0.43 2.78 0.14 9.30 0.90 Tarakihi TAR Nemadactylus macropterus 9 tier 3 4821.6 0.51 3.97 0.12 1220.58 0.10 Hapuku HAP Polyprion oxygeneios 7 tier 2 23.2 0.29 2.22 0.12 1.35 0.10 Bluenose BNS Hyperoglyphe antarctica 7 tier 3 1584.3 0.30 2.54 0.11 239.33 0.10 Redbait RBT Emmelichthys nitidus 4 tier 3 1242.7 0.39 3.07 0.12 240.55 0.50 Skate SKA Rajidae 9 tier 2 9.9 0.38 2.51 0.14 0.76 0.10 Orange roughy ORH Hoplostethus atlanticus 2 tier 3 78644.4 0.25 2.94 0.16 9974.00 0.10 Rough skate RSK Dipturus nasutus 9 tier 1 30.8 0.38 2.51 0.14 5.93 0.10 Rubyfish RBY Plagiogeneion rubiginosum 8 tier 3 85.6 0.45 2.93 0.14 19.34 0.10 Trumpeter TRU Latris lineata 8 tier 3 410.5 0.31 2.04 0.14 63.61 0.10 Jack mackerel JMD Trachurus declivis 5 tier 3 696.8 0.63 4.23 0.14 218.14 0.10 Gurnard GUR Chelidonichthys kumu 8 tier 2 0.16 0.74 4.67 0.15 0.024 0.10 Rig SPO Mustelus lenticulatus 9 tier 2 0.02 0.36 2.35 0.14 0.002 0.10 Gemfish SKI Rexea solandri 7 tier 3 65.9 0.34 2.79 0.12 11.33 0.10 Cardinalfish CDL Epigonus telescopus 7 tier 3 1543.0 0.38 2.39 0.15 290.61 0.10 Small demersal fish … … NA NA 458804.4 0.90 4.41 0.20 0 NA

118 Ecosystem Modelling of the Chatham Rise

References Anderson, O.F., Bagley, N.W., Hurst, R.J., Francis, M.P., Clark, M.R., McMillan, P.J., (1998). Atlas of New Zealand fish and squid distributions from research bottom trawls. NIWA Tech. Rep. 42, 1-303.

Anderson, O.F., Clark, M.R., Gilbert, D.J., (2000). Bycatch and discards in trawl fisheries for jack mackerel and arrow squid, and in the longline fishery for ling, in New Zealand waters. NIWA Tech. Rep. 74, 1-44.

Banse, K., Mosher, S., (1980). Adult body size and annual production / biomass relationships of field populations. Ecol. Monogr. 50, 355-379.

Bradford-Grieve, J.M., Probert, P.K., Nodder, S.D., Thompson, D., Hall, J., Hanchet, S., Boyd, P., Zeldis, J., Baker, A.N., Best, H.A., Broekhuizen, N., Childerhouse, S., Clark, M., Hadfield, M., Safi, K. and Wilkinson, I. (2003). Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology 289: 223-262.

Brett, J.R.; Groves, T.D.D. (1979). Physiological energetics. Pages 279-352 In: W.S. Hoar; D. J. Randall, J.R. Brett. (eds.). Fish Physiology. Vol VIII Academic Press, London, New York pp 279-352.

Bulman, C.M.; S.J.M. Blaber, (1986). Feeding ecology of Macruronus novaezelandiae (Hector) (Teleostei: Merlucciidae) in south-eastern Australia. Aust. J. Mar. Freshwat. Res. 37:621-639.

Clark, M.R., (1985). The food and feeding of seven fish species from the Campbell Plateau, New Zealand. N. Z. J. Mar. Freshwat. Res. 19, 339-363.

Clark, M.R., K.J. King, and P.J. McMillan, (1989). The food and feeding relationships of black oreo, Allocyttus niger, smooth oreo, Pseudocyttus maculates, and eight other fish species from the continental slope of the south-west Chatham Rise, New Zealand. Journal of Fish Biology, 35: 465-484.

Cohen, E.B. and Grosslein, M.D. (1987). Production on Georges Bank compared with other Shelf ecosystems. In: Backus, R.H. & Bourne, D.W. Georges Bank. MIT Press, Cambridge.

Connell, A.; Dunn, M.R.; Forman, J. (2010) Diet and dietary variation of New Zealand hoki Macruronus novaezelandiae. New Zealand Journal of Marine and Freshwater Research 44:289–308.

Horn, P.L.; M.R. Dunn (2010). Inter-annual variability in the diets of hoki, hake, and ling on the Chatham Rise from 1990 to 2009. New Zealand Aquatic Environment and Biodiversity Report No. 54, based on Project ENV2007-06. Pp 57.

Ecosystem Modelling of the Chatham Rise 119

Doonan, I.J.; M. Dunn; A. Dunford; A.C. Hart; D. Tracey (2006). Acoustic estimates of orange roughy abundance on the Northeastern and Eastern Chatham Rise, July 2004: wide-area survey and hill survey. New Zealand Fisheries Assessment Report 2006/58. ISSN 1175-1584. Pp 46.

Dunn, M.; Horn, P.; Connell, A.; Stevens, D.; Forman, J.; Pinkerton, M.; Griggs, L.; Notman, P.; Wood, B. (2009). Ecosystem-scale trophic relationships: diet composition and guild structure of middle-depth fish on the Chatham Rise. Final Research Report for Ministry of Fisheries Research Project ZBD2004-02, Objectives 1–5. 351 p.

Dunn, M.R.; Connell, A.; Forman, J.; Stevens, D.W.; Horn, P.L; (2010a). Diet of two large sympatric teleosts, the ling (Genypterus blacodes) and hake (Merluccius australis). PloS ONE 5(10): e13647. Doi:10.1371/journal.pone.0013647

Dunn, M.R.; Griggs, L.; Forman, J.; Horn, P.L. (2010b). Feeding habits and niche separation among the deep-sea chimaeroid fishes Harriotta raleighana, Hydrolagus bemisi and Hydrolagus novaezealandiae. Marine Ecology Progress Series 407: 209–225.

Dunn, M.R.; P.L. Horn; M.H. Pinkerton (submitted, 2013). Guild structure and biomass trends in a deep water fish assemblage.

FishBase, (2000). FishBase 2000: concepts, design and data sources. Edited by Froese, R. and D. Pauly, ICLARM, Los Baños, Laguna, Philippines. (http://www.fishbase.org/home.htm) pp 344.

Forman, J.S.; Dunn, M.R. (2010). The influence of ontogeny and environment on the diet of lookdown dory, Cyttus traversi. New Zealand Journal of Marine and Freshwater Research, 44: 329–342.

Forman, J.S.; Dunn, M.R. (in prep.) Diet and scavenging habits of the smooth skate Dipturus innominatus from Chatham Rise, New Zealand. Journal of Fish Biology

Horn, P.L.; Burrell, T.; Connell, A.; Dunn, M.R. (2011). A comparison of the diets of silver (Seriolella punctata) and white (Seriolella caerulea) warehous. Marine Biology Research 7: 576–591.

Horn P.L.; Dunn, M.R.; Forman, J. (in prep.). The diet of orange perch (Lepidoperca aurantia) on Chatham Rise, New Zealand. Journal of Applied Ichthyology

Horn P.L.; Forman, J.; Dunn, M.R. (2010) Feeding habits of alfonsino, Beryx splendens, on the Chatham Rise, New Zealand. Journal of Fish Biology 76: 2382–2400.

Horn P.L.; Forman, J.; Dunn, M.R. (2012). Dietary partitioning by two sympatric fish species, red cod (Pseudophycis bachus) and sea perch (Helicolenus percoides), on Chatham Rise, New Zealand. Marine Biology Research 8: 624–634.

Horn, P.L.; Forman, J.; Dunn, M.R. (in prep.). Moon phase influences the diet of Southern Ray’s Bream (Brama australis). Environmental Biology of Fishes

120 Ecosystem Modelling of the Chatham Rise

Ikeda, T., (1996). Metabolism, body composition, and energy budget of the mesopelagic fish Maurolicus muelleri in the Sea of Japan. Fish. Bull. 94, 49-58.

Livingston, M.E.; Clark, M.R.; Baird, S.-J. (2003). Trends in incidental catch of major fisheries on the Chatham Rise for fishing years 1989-90 to 1998-99. NZ Fisheries Assessment Report 2003/52, pp74.

McLusky, D.S. (1981). The estuarine ecosystem. Blackie Press, Glasgow.

Ministry of Fisheries Science Group (2009). Report from the Fisheries Assessment Plenary, May 2009: stock assessments and yield estimates. Ministry of Fisheries, Wellington, New Zealand.

Ministry of Fisheries Science Group (2011). Report from the Fisheries Assessment Plenary, May 2011: stock assessments and yield estimates. Ministry of Fisheries, Wellington, New Zealand.

Palomares, M.L.; D. Pauly. (1998). Predicting food consumption of fish populations as functions of mortality, food type, morphometrics, temperature and salinity. Marine and Freshwater Research, 49: 447-453.

Pankhurst, N.W.; Conroy, A.M. (1987). Size-fecundity relationships in the orange roughy, Hoplostethus atlanticus. New Zealand Journal of Marine and Freshwater Research 21: 295-300.

Parsons, T.R., Takahashi, M., Hargrave, B., (1984). Biological oceanographic processes. Pergamon Press Ltd, Oxford, 332 pp.

Probert, P.K. (1986). Energy transfer through the shelf benthos off the west coast of South Island, New Zealand. New Zealand Journal of Marine and Freshwater Research, 20, 407-417.

Rosecchi, E.; D.M. Tracey; W.R. Webber (1988). Diet of orange roughy Hoplostethus atlanticus (Pisces: Trachichthyidae) on the Challenger Plateau, New Zealand. Marine Biology, 99: 293-306.

Stevens, D.W.; Dunn, M.R. (2011). Different food preferences in four sympatric deep-sea Macrourid fishes. Marine Biology, 158: 59–72.

Stevens, D.W.; Dunn, M.R., Forman, J.; Connell, A. (in prep.). Diet of two Squaliforme sharks: Deania calcea and Squalus acanthias on Chatham Rise, New Zealand.

Stevens, D.W.; O’Driscoll, R.L.; Horn, P.L. (2009). Trawl survey of hoki and middle depth species on the Chatham Rise, January 2008 (TAN0801). New Zealand Fisheries Assessment Report 2009/18. 86 pages. Available at http://webcat.niwa.co.nz/documents/FAR2009-18.pdf

Stevens, D.W.; M.R. Dunn; M.H. Pinkerton; J.M. Bradford-Grieve. Feeding habits and niche separation in sympatric deep-sea Macrourid fishes. In prep.

Ecosystem Modelling of the Chatham Rise 121

Tuck, I.; Cole, R.; Devine, J.A. (2009). Ecosystem indicators for New Zealand fisheries. New Zealand Aquatic Environment and Biodiversity Report, October 2009. NIWA, Wellington. Pp. 180.

122 Ecosystem Modelling of the Chatham Rise

Appendix E Mesopelagics

Introduction This section details information for the trophic model of the Chatham Rise for middle-trophic level mesopelagic groups, namely: 1. Mesopelagic fishes (mainly myctophids) 2. Cephalopods (mainly pelagic squids), but including benthic octopods 3. Crustacean macrozooplankton (>20 mm) 4. Gelatinous zooplankton, including salps

Mesopelagic fishes Mesopelagic fish are a ubiquitous and often abundant component of temperate ecosystems. Mesopelagic fish over the Chatham Rise are primarily the myctophid lantern fishes Symbolophorus boops Richardson 1845 and Lampanyctodes hectoris Günther 1876, and the sternoptychid Maurolicus australis Hector 1875, often called pearlside (McClatchie & Dunford 2003). These species of mesopelagic fish are typically 5 cm in length and 1.3 g in weight. Work has shown that they often comprise a significant proportion of the diet of commercial fish species on the Chatham Rise and surrounding regions (e.g. Clark et al. 1989; Clark 1985). Also included in this group are juvenile fishes too large to be included in the macrozooplankton groups (>20 mm), but too small to be included in a fish group (approximately <20 cm).

Biomass Mesopelagic fish biomass on the Chatham Rise was estimated from fisheries acoustic surveys in November-December 2000 using new estimates of target strength to interpret the acoustic backscatter measurements (McClatchie & Dunford 2003; O’Driscoll et al., 2009). This work gives an estimate of 665,000 t of mesopelagic fish in the study region, with an uncertainty estimated to be 25%. In order to convert between wet weight and carbon we used the conversion factor of 0.1 gC gWW -1 for fish (Vinogradov, 1953; see Appendix D for more details).

Production The energetic parameters for the New Zealand mesopelagic fish stocks are not well known. Weight-specific production rates were estimated based on the allometric equations of Banse & Mosher (1980), and Haedrich & Merrett (1992) (see Appendix D for details). This led to estimate of P/B for mesopelagic fishes of 1.75 y -1. Published data on production rates for M. muelleri imply P/B=1.15 y -1 (Ikeda 1996). Similar P/B ratios (0.87–1.38 y -1) are given for mesopelagic fish off California (Childress et al. 1980). Here, we use an average of these i.e. P/B=1.4 y -1.

Consumption Consumption/biomass ratio for the mesopelagic fish assemblage was estimated as Palomares & Pauly ( 1998 ), giving a value of 16 y-1, which is towards the upper part of previous studies (10.6–16.7 y -1: Bradford-Grieve et al. 2003; Pakhomov et al. 1996). These consumption and production values imply a growth efficiency of P/Q=0.09. For comparison, in the trophic model of a New Zealand rocky reef ecosystem off east coast North Island,

Ecosystem Modelling of the Chatham Rise 123

small reef fish were estimated to have P/Q=0.15 while larger demersal and pelagic fishes had P/Q between 0.042 and 0.12 (Pinkerton et al. 2008; Lundquist & Pinkerton 2008). We assume P/Q of 0.20 for mesopelagic fishes and hence a Q/B of 7.1 y-1.

Diet The diet of M. muelleri is described by Ikeda et al. (1994), and includes a variety of meso- and macro-zooplankton species, especially copepods. Recent measurements of the diet of small mesopelagic fishes collected on the TAN1116 voyage to the Chatham Rise in November 2011 includes examination of 721 stomachs from 38 key species of myctophids (NIWA, unpublished data). These data are yet to be finalised but preliminary data confirm feeding on mesozooplankton (copepods, pteropods) and hard-bodied macrozooplankton (euphausiids). There is also evidence of feeding by myctophids on arthropods (decapods), soft-bodied zooplankton (salps, chaetognaths, polychaetes), fish (mainly other myctophids, but also juvenile fish and fish eggs), and macrobenthos (including a small number of bivalves).

Other information: EE, U, accumulation, imports, exports, transfers For this trophic model, we assumed that the majority of mesopelagic fish remain within the model region in the course of a year and set net import to zero. It is not known if mesopelagic fish populations within the study area are undergoing long- term, consistent change in terms of biomass. The model will assume no substantial and consistent change from year to year, i.e. we set accumulation to zero. Ecotrophic efficiency (E) is not known for mesopelagic fishes in the study area. The proportion of annual production leading to carcasses due to causes other than direct predation and fishing is not known but is assumed to be 1%, giving a base estimate of ecotrophic efficiency of 0.99. Mesopelagic fish are not caught by commercial fisheries so fisheries export is zero. Energy loss due to unassimilated consumption and excretion for mesopelagic fishes is not well known, but was assumed to follow the general Unassimilated consumption factors are not known for mesopelagic fishes in the study region and was assumed to be U=0.27 in the model as for carnivorous fish (Brett & Groves 1979).

Cephalopods (squid and octopods) Cephalopods are a major food source for a wide variety of predators, including fish, marine mammals and seabirds. By far the most common squid taken by fisheries on the Chatham Rise is the arrow squid ( Nototodarus sloani ). Other squid occurring on the Chatham Rise (Livingston et al. 2003) include warty squid ( Moroteuthis ingens, M. robsoni ), red squid (Ommastrephes bartrami ), and giant squid ( Architeuthis ) (Livingston et al. 2003). Warty, and red squids live deeper in the water column (Anderson et al. 1998), are caught in much small quantities by fisheries than arrow squid. Giant squid are found in waters 300–600 m deep south and east of New Zealand (Förch, 1998) . Note that this section deals with pelagic cephalopods (squids). Benthic octopods are considered in Appendix H and combined with data from this section to provide parameters for the cephalopod component of the trophic model.

124 Ecosystem Modelling of the Chatham Rise

Biomass Biomass of squid is exceptionally difficult to estimate given that squid are difficult to catch and have the potential for rapid changes in population size from year to year. Biomass estimates of squid caught in commercial fisheries on the Chatham Rise are not routinely estimated (Annela et al. 2003a, b). Selectivity of squid with commercial trawl gear are not known but are likely to be considerably lower than fish. If we assume that the selectivity of squid with trawl gear is half that of fast-swimming, similarly-sized demersal fish, we can obtain an order-of-magnitude estimate of squid biomass on the Chatham Rise. Doing so, leads to an estimate of adult (commercially-sized) squid biomass in the study region of 9,400 t. It is also necessary to estimate the biomass of small (sub-commercially sized squid). Work on the banding of statoliths from N. sloani suggests that the animals live for around 1 year, with rapid length growth of more than 3 cm per month (Gibson 1995; Annala et al. 2003). Using von Bertalanffy growth parameters and length-weight relationship from Annala et al. (2003) gives an estimate of typical adult weight of 350 gWW and a juvenile weight of 18 gWW. Juvenile mortality of squid on the Chatham Rise is unknown, but it is estimated that 946 out of every 1000 Todarodes pacificus (Japanese flying squid) die during the first 2 weeks of life (Gibson 1995), so perhaps of the order of 5% of squid survive to be of commercial catch size. Together, this implies that the biomass of sub-commercially sized squid is similar to that of commercially sized squid. We estimate a biomass for all pelagic squid on the Chatham Rise of 18,700 t. South of New Zealand, Hurst & Schofield (1995, Table 7) suggest that squid biomass appears to be about 1.8% of “all species biomass” in the same area. Here, we estimate total squid biomass is about 1.5% that of all demersal fishes, so this provides some suggestion that our estimate of squid biomass is of the right magnitude.

Research by Vlieg (1988) found arrow squid dry weight to be 22.5% of wet weight, and ash to be 6.2% of dry weight. If ash-free dry material is made of material in carbohydrate proportions (C 6H12 O6) then carbon is ~40% dry weight or 8.4% wet weight. Vinogradov (1953) gives similar data for dry weight of Cephalopoda ranging from 13-30% of wet weight and ash is 0.9–2.4% of wet weight. We note that there may be substantial variation in carbon content of cephalopods; muscular squids (such as Ommastrephes) may have carbon to wet weight ratio of 10% whereas ammoniacal squid (such as Histioleuthis) may have lower carbon content of ca. 5% (Clarke et al. 1996). However, the value of 8.4% used here is very similar to the carbon:wet weight ratio for squid which has been estimated to be ca. 8.3% (Brey 2005).

Production Cephalopods seem to be capable of exceptionally high growth rates compared to other invertebrates and fish (Boyle & Rodhouse 2005). Growth rates of squid are highly variable, and probably depend substantially on food intake (O’Dor et al. 1980; Boyle & Rodhouse 2005). Two-phase growth models are often used for cephalopods (Forsythe 1993), although two-phase growth is rarely obvious in field data (Boyle & Rodhouse 2005). In the two phase model, growth of cephalopod larvae is rapid (exponential) until adulthood. In adulthood, growth becomes slower and is often described by a power law (e.g. von Bertalanffy). Growth rates of cephalopods seems to depend substantially on food intake and may vary from near- zero somatic growth to a maximum of about 8% body weight per day (P/B=29 y -1) (Wells & Clarke 1996).

Ecosystem Modelling of the Chatham Rise 125

Von Bertalanffy growth parameters and length-weight relationships for arrow squid in the New Zealand EEZ are given in Ministry of Fisheries (2009) based on Gibson (1995) and Mattlin et al. (1985) respectively. Maximum dorsal mantle length of N. gouldi is 35 cm (Gibson & Jones 1993) and maximum weight is about 690 gWW. Ministry of Fisheries (2009) report: “Growth is rapid. Modal analysis of research data has shown increases of 3.0–4.5 cm per month for Gould's arrow squid measuring between 10 and 34 cm Dorsal Mantle Length (DML).” The length-weight and von Bertalanffy growth parameters (Mattlin et al. 1985; Gibson 1995) imply DML growth rates of between 3.3–5.6 cm month -1 for squid of DML 10– 20 cm, which are similar to those quoted by Ministry of Fisheries (2009). A much lower growth rate of 0.19 cm month-1 is implied by the time squid reach a DML of 34 cm. The growth rates of N. gouldi implied by these figures are reasonable, but towards the lower end of, somatic growth rates in the scientific literature. For arrow squid of DML 10–20 cm, values used here imply growth rates of 1.4–4.5 %WW d -1. In comparison, Illex illecebrosus is able to grow at rates up to 5 %WW d -1 (depending on the food intake) (see Wells & Clarke 1996 and references therein). Pecl et al. (2004) suggests squid growth rates of 4–9 %WW d -1 are likely. Boyle & Rodhouse (2005) summarise data on five species of squid which give somatic (growth) of 4.3 (0.6–11) %WW d -1.

The annual-average production rate of the whole squid population depends on the natural mortality of arrow squid which is unknown. Ministry of Fisheries (2009) report: “Recent work on the banding of statoliths from N. sloanii suggests that the animals live for around 1 year”. This agrees with observations of statolith increments (Jackson & O’Dor 2001) which showed that squids in temperate waters are likely to have lifespans of <1 year. It was estimated that 946 out of every 1000 Todarodes pacificus (Japanese flying squid) die during the first two weeks of life (Gibson 1995), implying a daily mortality rate of 0.21 d -1. Most of these will be larval squid however, and adult squid are likely to have substantially lower natural mortality. Here, we assume an age-independent natural mortality of M=0.01 d -1 for N. gouldi , with all surviving squid (2.6% recruiting adult squid) dying at 1 year old. This implies an average length of squid in the population of DML 16 cm, an average weight of 170 gWW.

Annual P/B ratios for gonatid squid in the Bering Sea are estimated to be 6.7 y-1 (Radchenko 1992), for Sthenoteuthis pteropus in the tropical Atlantic to be 8.0-8.5 (Lapitkhovskij 1995), and for captive Illex illecebrosus measured to be 2.9–9.1 y-1 at 7C (Hirtle et al. 1981). Boyle & Rodhouse (2005) summarise growth data on five species of squid which give P/B between 2.2 and 26 y -1. O’Dor et al. (1980) point out that growth rates of I. illecebrocsus from field data are well below those for captive animals, indicating that food supply of the natural population can be an important limiting factor. The von Bertalanffy growth parameters, natural mortality of 0.99 y -1 and fishing mortality selected to give the commercial squid catch, lead to P/B value for arrow squid >10 cm of 3.1 y -1. The von Bertalanffy growth parameters and length-weight relationship for arrow squid in Annala et al. (2003) suggest P/B of 26 y -1 for small squid (<10 cm). For the whole squid population, these can be combined to give an annual average P/B of 10.5 y -1. In the absence of other data, we average this estimate with those data from the literature, to obtain a final estimate of P/B of 8.6 y -1.

Consumption Gross growth efficiency for squid is reported as 20–40% (Boyle & Rodhouse 2005). Boyle & Rodhouse (2005) summarise data on five species of squid which give Q/B between 12 and 55 y -1, and P/Q between 0.11 and 0.35 (median value of 0.25). The apparently lower food

126 Ecosystem Modelling of the Chatham Rise

conversion efficiency of squid compared to octopus (median value P/Q=0.52) is accounted for by their greater use of energy for active movement (Boyle & Rodhouse 2005). The minimum survival consumption suggested by Wells & Clarke (1996) of 1.2–1.8 %WW d -1 corresponds to Q/B=4.4–6.6 y -1. The highest growth rates of Illex illecebrosus were achieved at food intake of about 10% body weight per day or Q/B=37 y -1 (Wells & Clarke 1996). The daily ration of Loligo pealei ranges from 3.2–5.8% of body weight per day (Vinogradov & Noskov, 1979) which represents a Q/B of 12–21 y -1. The mean daily ration of Illex illecebrosus is 5.2% (Hirtle et al. 1981) or a Q/B of 19 y -1. There are no measurements of squid consumption rates in the study area so here, we assume gross growth efficiency for arrow squid in the study area of P/Q=0.25, implying a consumption rate of Q/B=34 y -1.

Diet The diet of arrow squid has been reported to be made up of other squid (either intraspecific cannibalism or other species of squid), small pelagic and demersal fishes, and macro- and meso-zooplankton, especially large copepods, mysids, euphausiids, and decapod shrimps (Mattlin & Colman 1988; Hatanaka et al. 1989; Vinogradov & Noskov, 1979; Gibson 1995). Recently, Dunn (2009) examined the diet of arrow squid Nototodarus sloanii on the Chatham Rise. In all, the stomach contents of 388 specimens of length 14–41 cm DML were examined. Prey items were predominantly mesopelagic fishes (IRI 72%), with some crustaceans (IRI 6%) and cephalopods (IRI 10%). The most important nekton identified for the Chatham Rise were Maurolicus australis (Sternoptychidae), Lampanyctodes hectoris (Myctophidae) and unidentified squids (Teuthoidea).

Fishery removals We estimate commercial catches of arrow squid from the study area based on Quota Management System (QMS) reported catches in the 2009 Ministry of Fisheries plenary (Ministry of Fisheries 2009), from the fishing years 2003/2004 to 2007/2008. We assume that all catches are reported, and that 25% of the catch from SQU1T and SQU1J is from the study region, giving a recent annual average catch of arrow squid of about 12,700 t, or about 8% of the annual squid production (adults and juveniles combined).

Other information: EE, U, accumulation, imports, exports, transfers It is known that some species of squid can move considerable distances including seasonal migrations (Boyle & Rodhouse 2005; David Thompson, NIWA, pers. comm.). However, tagging experiments in New Zealand waters indicate that arrow squid move less than 5.6 km per day (Ministry of Fisheries 2009) and for this trophic model, we assumed that the majority of squid remain within the model region in the course of a year and set net import to zero.

It is not known if squid populations within the study area are undergoing long-term, consistent change in terms of biomass. The model will assume no substantial and consistent change from year to year, i.e. we set accumulation to zero.

Ecotrophic efficiency (E) is not known for squid in the study area. Ecotrophic efficiency measures the proportion of the annual production that is available for predation (“passed up the food chain”) as well as exported (including as fishery landings, migration, spawning output, growth) or accumulated. The remainder of the production (a fraction of 1-E) is transferred to a detrital group. In the case of squid, whole dead individuals or parts of squid are likely to be scavenged rather than decomposed by bacterial action and so will be passed

Ecosystem Modelling of the Chatham Rise 127

in the model to the carcass group. This material is from two sources. First, squid can die from causes other than direct predation, including starvation, disease, excessive parasite loading etc. However, it is likely that that the vast majority of squid mortality is likely to be due to direct predation rather than other causes. The proportion of annual production leading to carcasses due to causes other than direct predation and fishing is not known but is assumed to be 1%, giving a base estimate of ecotrophic efficiency of 0.99. Added to this is fishery catch of squid that is discarded back into the study area either as whole individuals (assumed dead) or as parts thereof. This is likely to be negligible as squid are landed whole.

Energy loss due to unassimilated consumption and excretion for squid is not well known, but was estimated for two species of squid ( Lilogo opalscens , Illex illecebrosus ) based on annual energy budgets (Boyle & Rodhouse 2005). The mean of these values imply U=0.13 which we will use here. We note that this is similar to the value of unassimilated consumption assumed for octopus, (U=0.12) but somewhat lower than the value of U=0.30 used generically in other trophic models (e.g. Christensen & Pauly 1992; Bradford-Grieve et al. 2003).

Macrozooplankton (hard-bodied) Hard-bodied macrozooplankton in the vicinity of the Subtropical Front are mainly euphausiids, although decapoda and amphipoda, are also present (e.g. Robertson et al., 1978). Euphausiids found during two recent voyages to the Chatham Rise (TAN0806, TAN1116) included: Euphausia longisrostris , E. lucens , E. similis, E. similis armata, Nematoscelis megalops, Stylocheiron maximum, Thysanapoda acutifrons , and Thysanoessa vicina , with total lengths up to 43 mm (median length 27 mm).

Biomass In general the biomass of macrozooplankton is poorly known over the Chatham Rise. Here, we used data collected on two recent surveys to the region, which used a combination of acoustic and trawl surveys: (1) voyage TAN0806, 23 May to 12 June 2008; (2) voyage TAN1116, 2–20 November 2011. The survey design in 2008 consisted of zig-zag survey transects with several pre-determined oceanographic sampling stations. The survey tracks were laid out to maximize area covered and access to key sampling stations. The design in 2011 was structured around eight strata with oceanographic sampling stations within each stratum. Acoustic data collection and underway upper-ocean water sampling was carried out whilst steaming between stations within strata and between strata. In each survey, the general approach was to identify key acoustic features (layers and aggregations) of the mesopelagic zone and perform target identification trawls to assess their species composition. Preliminary analysis of the acoustic and midwater trawl data from the two voyages in given in Gauthier et al. (submitted).

Two types of midwater trawling was carried out: (1) daytime “mark identification” trawls were used to assess species composition of acoustic marks; (2) night-time “oblique trawls” were carried out by hauling the net obliquely through the whole water column from the near bottom to near surface (Figure E1). Mark identification trawls were performed during the daytime when mesopelagic organisms tend to form discrete layers within the water column. The day trawls were often carried out on the layer or aggregation that constituted the main source of acoustic backscatter in the water column. However sometimes trawls were targeted on weaker acoustic layers or smaller fractions of the total backscatter if they were discrete and unfamiliar, particularly when other component of the water column were recognized as

128 Ecosystem Modelling of the Chatham Rise

belonging to a group already sampled. For this reason, the daytime trawl stations alone cannot be strictly treated as fully representative of the mesopelagic fauna at various locations, and care must be taken in interpreting these results. More detailed representations of the whole water column were obtained from night-time oblique mesopelagic trawls carried out at oceanographic stations during the 2011 survey.

To estimate depth-integrated (water column) abundance from oblique trawls, we multiply the average volumetric abundance by the water depth. To estimate depth-integrated (water column) biomass from mark identification trawls, we multiply the average volumetric abundance by the thickness of the mark/layer sampled, assuming that the majority of the biomass is contained in the layer of interest. This will tend to lead to underestimates of the actual abundance if there is biomass distributed outside the layer sampled. We estimate that the sampling by the mesopelagic trawl may be representative of abundance in a layer of thickness 50 m on average. As krill swarms are very patchy (see Figure E2) the appropriate value to use depends on whether the trawl managed to sample the spots of high krill abundance or not.

Data shown in Gauthier et al. (submitted) suggests that euphausiids may have a mean numerical density in the study area at depths of less than 500 m of 1.0 ind m -2. At depths greater than 500 m, krill density may be lower, at an estimated 0.1 ind m -2. For the study area as a whole, krill density is estimated as 0.48 ind m -2. Note that this is based on a selectivity of 1 for krill by the midwater trawl. All trawling on TAN0806 and TAN1116 was carried out using the NIWA fine-mesh midwater trawl. This trawl has a mouth opening of about 19 m diameter, and a codend mesh of 10 mm. We assume a selectivity of 0.5 to account for krill lost through the mesh and hence a mean krill density for the study area of 0.95 ind m -2. At median length 27 mm, the individual weight of krill is likely to be approximately 0.4 gWW ind -1. The total biomass of krill in the model area is hence estimated to be 89,000 tWW. If we assume krill makes up a nominal 75% of total macrozooplankton biomass in the study area, the total mass of macrozooplankton in the study region is 120,000 tWW. This is a biomass density of 0.53 gWW m -2. Wet weight of macrozooplankton was converted to carbon using a value of 5.5% for the carbon/wet weight ratio (Ikeda & Kirkwood, 1989; Weibe 1988; Pinkerton et al. 2010). This is consistent with dry weight for macrozooplankton of c. 13% of wet weight (Weibe, 1988) and measurements of the carbon content of isotope samples of krill measured at NIWA of 42.0±3.2% (mean±sd) (Pinkerton, unpublished data). The biomass density of hard-bodied macrozooplankton is the study area is hence estimated as 0.022 gCm-2.

Ecosystem Modelling of the Chatham Rise 129

Figure E1: Spatial distribution of catch rates (individuals per unit volume) of euphausiids over the Chatham Rise (Gauthier et al., submitted, Figure 4). Colours correspond to voyage and trawl type (green = TAN0806 mark identification, blue = TAN1116 mark identification, orange = TAN1116 oblique). Depth contours are at 500 and 2000 m.

Figure E2: Example echogram for the krill acoustic category. The echogram was obtained with the 38 kHz data and represents volume backscattering strength in dB (colour scale) for a distance of 1 nautical mile and a vertical extent of 100 m, with the upper and lower depth limits indicated (Gauthier et al., submitted, Figure 6j).

Production Production rates for macrozooplankton in the Chatham Rise are not well known and P/B value is estimated consistent with the literature (Table E1). Euphausia lucens has P/B=10.1- 16 y-1 (Stuart & Pillar, 1988) which is high relative to that of Nematoscelis megalops (5–6 y -1) (Lindley, 1982). Cartes & Maynou (1998) use P/B ranging from 1.24–4.75 for euphausiids and 8.05 for peracarids. Here we use P/B=8 y-1.

130 Ecosystem Modelling of the Chatham Rise

Table E1: P/B (y -1) for macrozooplankton over a range of marine ecosystems from around the world.

Macro - Location Reference zooplankton P/B (y -1) 6.1 North British Columbia, Canada Ainsworth et al. 2002, Beattie 2001 10 NZ Southern Plateau Bradford-Grieve et al. 2003 3 Nova Scotia coast to edge of shelf 1995 to Bundy 2004 2000 21 South Catalan Sea: coastal 50 m to 400 m: Coll et al. 2006 oligotrophic system 7.5 Baltic Sea Harvey et al. 2003 13 North Benguela Upwelling coast to shelf Heymans & Baird 2000 3.4 Newfoundland Heymans 2003 3.98 Gulf St Lawrence Canada Morissette et al. 2003 12 Central Chile upwelling coast to 30 Nautical Neira & Arancibia 2004 miles hake, 1992 7 USA mid-Atlantic Bight; temperate continental Okey 2001 shelf to 200m 13 SE USA Tropical continental shelf intertidal to Okey & Pugliese 2001 500m 25 Monterrey Bay California Olivieri et al. 1993 10 Te Tapuwae o Rongokako, East coast New Lundquist & Pinkerton 2008; Zealand, to 50 m Pinkerton et al. 2008 13 South Benguela Upwelling coast to shelf Shannon et al. 2003 5 East Bering Sea; temperate shelf down to Trites et al. 1999 500m 8 Chatham Rise This Study

Consumption Stuart & Pillar (1990) show that for E. lucens , 5-14% of body C d -1 was ingested by adults and Q/B ranged from 17–51 y -1. Based on a P/Q of 0.3, we estimate a consumption rate of Q/B=27 y-1.

Diet The diet of hard-bodied macrozooplankton (here taken as dominated by euphausiids) will include phytoplankton, microzooplankton, and mesozooplankton with copepods dominating the diet (Barange et al., 1991). Stuart & Pillar (1990) show that E. lucens is an omnivore that ingests on a carbon specific basis 15-60% phytoplankton, the remainder being mainly small copepods. Therefore we assume that macrozooplankton consume phytoplankton, microzooplankton, mesozooplankton and other hard-bodied and soft-bodied macrozooplankton. Better information on diets and trophic position of macrozooplankton on the Chatham Rise will be available soon when sample and data analysis from the TAN0806 and TAN1116 voyages has been completed.

Ecosystem Modelling of the Chatham Rise 131

Other information: EE, U, accumulation, imports, exports, transfers For this trophic model, we assumed that the majority of macrozooplankton remain within the model region in the course of a year and set net import to zero.

It is not known if macrozooplankton populations within the study area are undergoing long- term, consistent change in terms of biomass. The model will assume no substantial and consistent change from year to year, i.e. we set accumulation to zero.

Ecotrophic efficiency (E) is not known for macrozooplankton in the study area. The proportion of annual production leading to carcasses due to causes other than direct predation and fishing is not known but is assumed to be 5%, giving a base estimate of ecotrophic efficiency of 0.95. Macrozooplankton are not caught by commercial fisheries so fisheries export is zero.

Energy loss due to unassimilated consumption and excretion for macrozooplankton is not well known, but was assumed to be 0.4.

Macrozooplankton (soft-bodied) The soft-bodied macrozooplankton group includes all gelatinous pelagic zooplankton, including jellyfish (medusa), salps (Iasis zonaria , Salpa fusiformis , Salpa thompsoni ), siphonophores and chaetognaths (including Eukrohnia sp., Sagitta maxima , S. gazellae , S. marri , S. plauctiny and S. zetosios ). Salps ( Thaliacea ), and other gelatinous plankton occur throughout the Chatham Rise but their abundances, life-histories, trophic role, and energetics are poorly known. Gelatinous macrozooplankton can impact planktonic communities through intense grazing, and by affecting export of material from the upper ocean (Alldredge & Madin l982; Zeldis et al. 1995). Gelatinous plankton are opportunistic colonizers, and their population sizes can rapidly increase when conditions are favourable (Zeldis et al. 1995; Paffenhofer & Lee 1988). Thaliacean blooms are common in continental slope, shelf and coastal seas (e.g. Paffenhofer & Lee 1988; Paffenhofer et al. 1995; Zeldis et al. 1995; Boysen-Ennen et al. 1991; Pakhomov et al. 2002). Salps and gelatinous zooplankton can also be important food items for seabirds and some species of fish (notably, oreos). Gelatinous zooplankton abundance and biomass can vary greatly inter-annually and seasonally due to their opportunistic feeding behaviour which enables a rapid response to environmental changes by increasing feeding, growth, and reproduction in optimal conditions (Brodeur et al. 2008). It is this ability to boom or bust that has led to the suggestion that jellyfish in particular should be a key indicator species of changing climate conditions (Hay, 2006; Richardson et al., 2009).

Biomass Biomass of soft-bodied macrozooplankton in the Chatham Rise is not well known. As for hard-bodied macrozooplankton, biomass of soft-bodied macrozooplankton is estimated from data collected on two recent research voyages to the Chatham Rise: (1) voyage TAN0806, 23 May to 12 June 2008; (2) voyage TAN1116, 2–20 November 2011. Details are given in Gautier et al. (submitted). Data on salp abundance from daytime “mark identification” midwater trawls and night-time “oblique trawls” are shown in Figure E3. Depth-integrated (water column) abundance for salps was calculated by multiplying the average volumetric abundance by the total water depth for both types of trawl because no mark identification

132 Ecosystem Modelling of the Chatham Rise

trawl specifically targeted salps (as these have a low backscatter efficiency). Data shown in Gauthier et al. (submitted) suggests that salps may have a higher mean numerical density in the study area in colder waters to the south of the Subtropical Front than to the north. Mean depth-integrated densities to the south of the front were 0.67 ind m -2 and to the north were 0.31 ind m -2. We use the 12.5°C isobath as the approximate position of this division between colder water and warmer water (Figure E4). In total, 31% of the Chatham Rise study area is in this colder water and 69% in the warmer water, giving an overall estimation of salp density of 0.42 ind m -2. Note that this is based on a selectivity of 1 for salps by the midwater trawl. All trawling on TAN0806 and TAN1116 was carried out using the NIWA fine-mesh midwater trawl. This trawl has a mouth opening of about 19 m diameter, and a codend mesh of 10 mm. We assume a selectivity of 0.5 to account for salps (or parts of salps) lost through the mesh and hence a mean salp density for the study area of 0.85 ind m -2.

Salps measured on the TAN1116 voyage to the Chatham Rise In November 2011 had lengths 20–91 mm (median 40 mm) for species Iasis zonaria , Salpa fusiformis and S. thompsoni (Pinkerton, unpublished data). Volume-length and salp density data from Wiebe et al. (2010) for similarly-sized specimens of S. thompsoni leads to an estimate of individual weight of salps on the Chatham Rise of about 3.4 gWW ind -1. We hence estimate a salp biomass density of 2.8 gWW m -2. The total salp biomass in the model area is hence estimated to be 630,000 tWW. If we assume salps make up a nominal 75% of total gelatinous zooplankton biomass in the study area, the total mass of gelatinous zooplankton in the study region is 850,000 tWW. This is a biomass density of 3.8 gWW m -2.

Taking DW:WW ratio for salps of 5% (Dubischar et al. 2006) and measurements of the C:DW ratio of Southern Ocean samples measured at NIWA of 14.1±1.3% (salps, mean±sd, n=3) and 25.2±6.6% (jellyfish, n=5) (Pinkerton, unpublished data) gives estimates of C:WW of 0.56% (salps) and 1.0% (jellyfish). For comparison, Curl (1961) gives C:WW for salps of 0.37%. Using an overall C:WW ratio for gelatinous zooplankton on the Chatham Rise of 0.7% we estimate a biomass density of gelatinous macrozooplankton in the study area of 27 mgCm -2. For comparison, Atkinson et al. (2004) show salp densities in the Ross Sea of equivalent to a carbon density of approximately 2–60 mgC m -2. Pakhomov et al. (2002) suggests typical salp concentrations through the Subantarctic and Southern Ocean of 0.1–30 mgC m -2.

Ecosystem Modelling of the Chatham Rise 133

Figure E3: Spatial distribution of catch rates (individuals per unit volume) of salps over the Chatham Rise (Gauthier et al., submitted, Figure 4). Colours correspond to voyage and trawl type (green = TAN0806 mark identification, blue = TAN1116 mark identification, orange = TAN1116 oblique). Depth contours are at 500 and 2000 m.

134 Ecosystem Modelling of the Chatham Rise

Figure E4: Top: Long-term annual average sea-surface temperature over the Chatham Rise obtained from MODIS-Aqua data (2002–2012). High values are red; low values are blue (range 10.5°C–15.3°C). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m. Bottom: Same data, but water colder than 12.5°C is shown in purple.

Consumption Production rates of salps can be high (Zeldis et al. 1995), and are likely to be greater than other macrozooplankton, or P/B=10 y-1. Gross growth efficiency, P/Q, is likely to be greater than that of other zooplankton and has been estimated to be 0.40 (Jonsson 1986; Caron & Goldman 1990). These allow us to estimate Q/B=25 y-1. Unassimilated consumption of salps is estimated to be 0.5 (Anderson 1986)

Ecosystem Modelling of the Chatham Rise 135

Diet Thaliaceans are very efficient grazers, feeding by pumping water through a fine mucous net suspended in the pharyngeal cavity. They can retain and ingest virtually all cell sizes from nanoplankton to net-plankton (Alldredge & Madin l982), and so are assumed to feed on phytoplankton, organic detritus and associated bacteria, micro-, meso- and macro- zooplankton in the model.

Other information: EE, accumulation, imports, exports, transfers For this trophic model, we assumed that the majority of soft-bodied macrozooplankton remain within the model region in the course of a year and set net import to zero.

It is not known if soft-bodied macrozooplankton populations within the study area are undergoing long-term, consistent change in terms of biomass. The model will assume no substantial and consistent change from year to year, i.e. we set accumulation to zero.

Ecotrophic efficiency (E) is not known for soft-bodied macrozooplankton in the study area. The proportion of annual production leading to carcasses due to causes other than direct predation and fishing is not known but is assumed to be 5%, giving a base estimate of ecotrophic efficiency of 0.95. Soft-bodied macrozooplankton are not caught by commercial fisheries so fisheries export is zero.

References Ainsworth, C.; Heymans, S.; Pitcher, T.J.; Vasconcellos, M. (eds) (2002). Ecosystem Models of Northern British Columbia for the Time Periods 2000, 1950, 1900 and 1750 FCRR 2002, Vol. 10(4) 41 pp.

Alldredge, A.L.; L.P. Madin (1982). Pelagic tunicates: Unique herbivores in the marine plankton. Bio. Sci. 32:655-661.

Andersen, V. (1986). Effect of temperature on the filtration rate and percentage of assimilation of Salpa fusiforrnis Cuvier (Tunicata: Thaliacea). Hydrobiologia 137:135-140.

Annala, J.H.; Sullivan, K.J.; O’Brien, C.J.O.; Smith, N.W.McL.; Grayling, S.M., (2003). Report from the Fishery Assessment Plenary, May 2003: stock assessments and yield estimates, Parts 1 and 2. NZ Ministry of Fisheries, pp 616.

Atkinson, A.; Siegel, V.; Pakhomov, E.; Rothery, P. (2004). Long-term decline in krill stock and increase in salps within the Southern Ocean. Nature 432: 100-103.

Banse, K.; Mosher, S. (1980). Adult body size and annual production/ biomass relationships of field populations. Ecological Monographs 50: 355-379.

136 Ecosystem Modelling of the Chatham Rise

Barange, M., Gibbons, M.J., Carola, M., (1991). Diet and feeding of Euphausia hanseni and Nematoscelis megalops (Euphausiacea) in the northern Benguela Current: ecological significance of vertical space partitioning. Mar. Ecol. Prog. Ser. 73, 173-181.

Beattie, A.I. (2001). A New Model for Evaluating the Optimal Size, Placement and Configuration of Marine Protected Areas. Unpublished Masters thesis. Department of Resource Management and Environmental Science, University of British Columbia, 58pp.

Boyle, P.R.; Rodhouse, P. (2005). Cephalopods: ecology and fisheries. Blackwell Publishing, Pp. 452.

Boysen-Ennen, E.; Hagen, W.; Hubold, G.; Piatkowski, U. (1991). Zooplankton biomass in the ice-covered Weddell Sea, Antarctica. Mar. Biol. 111: 227-235.

Bradford-Grieve, J.M.; Probert, P.K.; Nodder, S.D.; Thompson, D.; Hall, J.; Hanchet, S.; Boyd, P.; Zeldis, J.; Baker, A.N.; Best, H.A.; Broekhuizen, N.; Childerhouse, S.; Clark, M.; Hadfield, M.; Safi, K.; Wilkinson, I. (2003). Pilot trophic model for sub Antarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology 289: 223–262.

Brett, J.R.; Groves, T.D.D. (1979). Physiological energetics. Pages 279-352 In: W.S. Hoar; D. J. Randall, J.R. Brett. (eds.). Fish Physiology. Vol VIII Academic Press, London, New York pp 279-352.

Brey, T. (2005). Population dynamics in benthic invertebrates: a virtual handbook. Alfred Wegener Institute. www.awi-bremerhaven.de/Benthic/Ecosystem/ FoodWeb/Handbook/main.html. (website accessed 1 April 2005).

Brodeur, R.D.; Decker M.B.; Ciannelli, L.; Purcell, J.E.; Bond, N.A.; Stabeno, P.J.; Acuna, E.; Hunt Jr, G.L. (2008). Rise and fall of jellyfish in the eastern Bering Sea in relation to climate regime shifts. Progress in Oceanography 77(2-3): 103-111.

Bundy, A. (2004). Mass balance models of the eastern Scotian Shelf before and after the cod collapse and other ecosystem changes. Canadian Technical Report of Fisheries and Aquatic Sciences No.2520. pgs.193.

Cartes, J.E., Maynou, F., (1998). Food consumption by bathyal decapod crustacean assemblages in the western Mediterranean: predatory impact of megafauna and the food consumption-food supply balance in the deep-water food web. Mar. Ecol. Prog. Ser. 171, 233-246.

Childress, J.J., Taylor, S.M., Cailliet, G.M., Price, M.H., (1980). Patterns of growth, energy utilization and reproduction in some meso- and bathypelagic fishes off southern California. Mar. Biol. 61, 27-40.

Christensen, V.; Pauly, D. (1992). The ECOPATH II - a software for balancing steady-state ecosystem models and calculating network characteristics. Ecological Modelling 61:169-185.

Ecosystem Modelling of the Chatham Rise 137

Clark, M.R. (1985). The food and feeding of seven fish species from the Campbell Plateau, New Zealand. New Zealand Journal of Marine and Freshwater Research 19: 339–363.

Clark, M.R., K.J. King, and P.J. McMillan, (1989). The food and feeding relationships of black oreo, Allocyttus niger, smooth oreo, Pseudocyttus maculates, and eight other fish species from the continental slope of the south-west Chatham Rise, New Zealand. Journal of Fish Biology 35, 465-484.

Clarke, M.R.; Martins, H.R.; Pascoe, P. (1996). The Diet of Sperm Whales (Physeter macrocephalus Linnaeus 1758) off the Azores. Philosophical Transactions of the Royal Society of London, B., 339(1287):67-82.

Coll, M.; Palomera, I.; Tudela, S.; Sardá, F. (2006). Trophic flows, ecosystem structure and fishing impact in the South Catalan Sea, Northwestern Mediterranean Sea. Journal of Marine Ecosystems 59: 63-96.

Curl, H. (1961). Standing crops of carbon, nitrogen, and phosphorous, and transfer between trophic levels, in continental shelf waters south of New York. Rapp P-v Cons Reun int Explor Mer 153:183-189.

Dubischar, C.; Bathmann, U.V. (1997). Metazooplankton grazing across frontal systems in the Southern Ocean. Deep-Sea Research Part II 44: 415-433.

Dunn, M.R. (2009). Feeding habits of the ommastrephid squid Nototodarus sloanii on the Chatham Rise, New Zealand. NZ Journal of Marine and Freshwater Research, 43: 1103–1113.

Förch, E.C., (1998). The marine fauna of New Zealand: Cephalopoda: Oegopsida: Architeuthidae (giant squid). NIWA Biodiv. Mem. 110, 1-113.

Forsythe, J.W. (1993). A working hypothesis of how seasonal temperature change may impact the field growth of young cephalopods. In: Okutani T., O'Dor, R., Kubodera, T. (Eds.), Recent Advances in Cephalopod Fisheries Biology. Tokai University Press, Tokyo, pp. 133-143.

Gauthier, S.; J. Oeffner; R.L. O’Driscoll (2013). Species composition and acoustic signatures of mesopelagic organisms in a subtropical convergence zone, the New Zealand Chatham Rise. Submitted to PLoS One.

Gibson D., Jones JB. (1993). Fed up with parasites? — old fish are. Marine Biology 117: 495–500.

Gibson, D.J.M. (1995). The New Zealand squid fishery 1979-93. New Zealand Fisheries Technical Report No. 42, pp43.

Haedrich, R.L.; Merrett, N.R. (1992). Production/biomass ratios, size frequencies, and biomass spectra of deep-sea demersal fishes. Pp. 157–182 in Rowe, G.T.; Pariente, V. (Eds): Deep-Sea food chains and the global carbon cycle. Kluwer Academic Publishers, Dordrecht.

138 Ecosystem Modelling of the Chatham Rise

Harvey, C. J.; Cox, S. P.; Essington, T. E.; Hansson, S.; and Kitchell, J. F. (2003). An ecosystem model of food web and fisheries interactions in the Baltic Sea. ICES Journal of Marine Science, 60: 939–950.

Hatanaka, H.; Uozumi, Y.; Fukui, J.; Aizawa, M.; Hurst, R.J. (1989). Japan-New Zealand trawl survey off southern New Zealand, October-November 1983. MAFish N. Z. Fish. Tech. Rep., Wellington 9, 1-51.

Hay, S., (2006). Gelatinous bells may ring change in marine ecosystems. Current Biology 16; 679–682.

Heymans, J.J. (ed.) (2003). Ecosystem models of Newfoundland and Southeastern Labrador: Additional information and analyses for 'Back to the Future' FCRR 2003, Vol. 11(5) 79 pp.

Heymans, J.J.; Baird, D., (2000). Network analysis of the northern Benguela ecosystem by means of NETWRK and ECOPATH. Ecological Modelling 131: 97– 119.

Hirtle, R.W.M.; DeMont, M.E.; O’Dor, R.K. (1981). Feeding, growth, and metabolic rates in captive short-finned squid, Illex illecebrosus, in relation to the natural populations. J. Shellfish Res. 1, 187-192.

Hurst. R.J.; Schofield, K.A. (1995). Winter and summer trawl surveys of hoki south of New Zealand, 1990. N. Z. Fish. Tech. Rep. 43, 1-55.

Ikeda, T. (1996). Metabolism, body composition, and energy budget of the mesopelagic fish Maurolicus muelleri in the Sea of Japan. Fishery Bulletin 94: 49–58.

Ikeda, T., Hirakawa, K., Kajihara, N., (1994). Diet composition and prey size of the mesopelagic fish Maurolicus muelleri (Sternoptychidae) in the Japan Sea. Bull. Plankton Soc. Jap. 41, 105-116.

Ikeda, T.; Kirkwood, R. (1989). Metabolism and body composition of two euphausiids (Euphausia superba and E. crystallorophias) collected from under the pack-ice off Enderby Land, Antarctica. Marine Biology 100: 301-308.

Jackson, G.D.; O’Dor, R.K. (2001). Time, space and the ecophysiology of squid growth, life in the fast lane. Vie Milieu 51: 205-215.

Laptikhovsky V.V. (1995). Mortality and production of the squid Sthenoteuthis pteropus (Steenstrup) (Oegopsida, Ommastrephidae) in the eastern tropical Atlantic. V.A. Sushin (ed.). Biology and population dynamics of fishes and invertebrates in the Atlantic Ocean. Kaliningrad: AtlantNIRO Press: 142-154 (In Russian with English abstract)

Lindley, J.A. (1982). Population dynamics and production of euphausiids. 4. Euphausia krohni, Nematoscelis megalops and Thysanoessa gregaria, and eight rare species in the North Atlantic Ocean. Marine Biology 71(1): 1-6.

Ecosystem Modelling of the Chatham Rise 139

Livingston, M.E., Clark, M.R. and Baird, S.-J., (2003). Trends in incidental catch of major fisheries on the Chatham Rise for fishing years 1989-90 to 1998-99. NZ Fisheries Assessment Report 2003/52, pp74.

Lundquist, C.J.; M.H. Pinkerton (2008). Collation of data for ecosystem modelling of Te Tapuwae o Rongokako Marine Reserve. Science for conservation 288, published July 2008, Department of Conservation, Wellington, New Zealand.

Mattlin, R.H.; Colman, J.A., (1988). Arrow squid. N. Z. Fish. Assessment Doc. 88/34, 16 pp. Unpublished document, New Zealand Ministry of Agriculture and Fisheries, Fisheries Research Centre.

Mattlin, R.H.; Scheibling, R.E.; Förch, E.C. (1985). Distribution, abundance and size structure of arrow squid (Nototodarus sp.) off New Zealand. NAFO Scientific Council Studies 9: 39–45.

McClatchie, S.; Dunford, A., (2003). Estimated biomass of vertically migrating fish mesopelagic fish off New Zealand. Deep-Sea Research I, 50, 1263-1281.

Ministry of Fisheries (2009). Report from the Fishery Assessment Plenary, May 2009: stock assessments and yield estimates. Unpublished report in 3 volumes held in NIWA library, Wellington. 1035 p.

Morissette, L.; Despatie, S.; Savenkoff, C.; Hammill, M.O.; Bourdages, H.; Chabot, D. (2003). Data gathering and input parameters to construct ecosystem models for the northern Gulf of St. Lawrence (mid-1980s). Canadian Technical Report of Fisheries and Aquatic Sciences 2497. pgs 94.

Neira, S.; Arancibia, H. (2004). Trophic interactions and community structure in the upwelling system off Central Chile (33–398S). Journal of Experimental Marine Biology and Ecology 312: 349–366

O’Dor, R.K.; Durwald, R.D.; Vessey, E. (1980). Feeding and growth in captive squid, Illex illecebrosus, and the influence of food availability on growth in the natural population. Selected Papers, International Commission of Northwest Atlantic Fisheries 6, 15-21.

O’Driscoll, RL, Gauthier, S, Devine, JA (2009). Acoustic estimates of mesopelagic fish: as clear as day and night? ICES Journal of Marine Science 66: 1310–1317.

Okey, T.A. (2001). A ‘straw-dog Ecopath model of the Middle Atlantic Bight continenta; shelf United States. In: Guénette, S., Christensen, V., Pauly, D. (eds), Fisheries Impacts on North Atlantic Ecosystems: Models and Analyses. Fisheries Centre Research Reports 9(4): 151-166.

Okey, T.A.; Pugliese, R. (2001). A Preliminary Ecopath Model of the Atlantic Continental Shelf adjacent to the south-eastern United States. In: Guénette, S., Christensen, V., Pauly, D. (eds), Fisheries Impacts on North Atlantic Ecosystems: Models and Analyses. Fisheries Centre Research Reports 9(4): 167-181.

140 Ecosystem Modelling of the Chatham Rise

Olivieri, R.A.; Cohen, A; Chavez, F.P. (1993). An ecosystem model of Monterey Bay, California, pp. 315-322. In: V. Christensen and D. Pauly (eds.) Trophic models of aquatic ecosystems. ICLARM Conf. Proc. 26.

Paffenhofer, G-A.; L.P. Atkinson; T.N. Lee; P.G. Verity; L.R. Bulluck III. (1995). Distribution and Abundance of Thaliaceans and Copepods off the Southeastern U.S.A. during Winter. Cont. Shelf Res.: 15, 255-280.

Paffenhofer, G-A.; T.N. Lee (1988). Development and persistence of patches of thaliacea. The Benguela and Comparable Ecosystems, Payne, A.I.L., Gulland, J.A. and K.H. Brink (Eds). S. Afr. J. Mar. Sci.: 5, 305-318.

Pakhomov, E.A., Perissinotto, R., McQuaid, C.D., (1996). Prey composition and daily rations of myctophid fishes in the Southern Ocean. Mar. Ecol. Prog. Ser. 134, 1-14.

Pakhomov, E.A.; Froneman, P.W.; Perissinotto, R. (2002). Salp/krill interactions in the Southern Ocean: spatial segregation and implications for the carbon flux. Deep Sea Res II 49:1881–1907.

Palomares, M.L.; D. Pauly (1998). Predicting food consumption of fish populations as functions of mortality, food type, morphometrics, temperature and salinity. Marine and Freshwater Research, 49, 447-453.

Pecl, G.T.; Steer, M.A.; Hodgson, K.E. (2004). The role of hatchling size in generating the intrinsic size-at- age variability of cephalopods: extending the Forsythe Hypothesis. Marine and Freshwater Research 55: 387-394

Pinkerton, M.H.; C.J. Lundquist; C.A.J. Duffy; D.J. Freeman (2008). Trophic modelling of a New Zealand rocky reef ecosystem using simultaneous adjustment of diet, biomass and energetic parameters. Journal of Experimental Marine Biology and Ecology 367 (2008) 189–203.

Pinkerton, M.H.; J.M. Bradford-Grieve; S.M. Hanchet (2010). A balanced model of the food web of the Ross Sea, Antarctica. CCAMLR Science, 17: 1–31.

Radchenko, V.I. (1992). The role of squids in the pelagic ecosystem of the Bering Sea. Oceanol. 32, 762-767. [English translation]

Richardson, A. J.; Bakun, A.; Hays G. C.; Gibbons M. J. (2009). The jellyfish joyride: causes, consequences, and management responses to a more gelatinous future. Trends Ecological Evolution. 24: 312–322.

Robertson, D.A., Roberts, P.E., Wilson, J.B., (1978). Mesopelagic faunal transition across the Subtropical Convergence east of New Zealand. N. Z. J. Mar. Freshwat. Res. 12, 295-312.

Shannon, L.J.; Moloney,C.L.; Jarre A .; Field, J.D. (2003). Trophic flows in the southern Benguela during the 1980s and 1990s. Journal of Marine Systems 39: 83–116.

Ecosystem Modelling of the Chatham Rise 141

Stuart V., Pillar, S.C., (1988). Growth and production of Euphausia lucens in the southern Benguela current. J. Plankton Res. 10, 1099-1112.

Trites, A.W.; Livingston, P.A..; Mackinson, S.; Vasconcellos, M.C.; Springer, A.M.; Pauly, D. (1999). Ecosystem change and the decline of marine mammals in the Eastern Bering Sea: Testing the ecosystem shift and commercial whaling hyotheses. Fisheries Centre Research Reports 7(1): 106.

Vinogradov, A.P. (1953). The elementary chemical composition of marine organisms. Memoir of the Sears Foundation for Marine Research, Yale University, New Haven II, 647 pp.

Vinogradov, V.I.; Noskov, A.S. (1979). Feeding of short-finned squid, Illex illecebrosus, and long-finned squid, Loligo pealei, off Nova Scotia and New England, 1974-75. Selected Papers, I.C.N.A.F. 5: 31-36.

Vlieg, P. (1988). Proximate composition of New Zealand marine finfish and shellfish. Biotechnology Division, DSIR, Palmerston North, New Zealand.

Weibe, P.H., (1988). Functional regression equations for zooplankton displacement volume, wet weight, dry weight, and carbon: a correction. Fish. Bull. 86(4), 833- 835.

Wells, M.J.; Clarke, A. (1996). Energetics: the cost of living and reproducing for an individual cephalopod. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences, 351: 1083–1104.

Wiebe, P. H., Chu, D., Kaartvedt, S., Hundt, A., Melle, W., Ona, E., and Batta-Lona, P. (2010). The acoustic properties of Salpa thompsoni. ICES Journal of Marine Science, 67: 583–593.

Zeldis J.R.; Davis C.S.; James M.R.; Ballara S.L.; Booth W.E.; Chang F.H. (1995). Salp grazing: effects on phytoplankton abundance, vertical distribution and taxonomic composition in a coastal habitat. Marine Ecology Progress Series 126:267–283.

142 Ecosystem Modelling of the Chatham Rise

Appendix F Phytoplankton

Introduction All the primary production in the Chatham Rise ecosystem is due to phytoplankton in the upper ocean overlying the rise. This productivity is, in turn, related to the concentrations of macro-nutrients (nitrate, phosphate, silicate), micro-nutrients (iron), light availability, and water column stability (Boyd et al. 1999). Phytoplankton abundance and primary production vary spatially, seasonally and inter-annually, and cannot be adequately characterised at large space scales (>10s km) and over long-time periods (decades) from shipboard sampling. Instead, we use remote measurements of ocean colour from radiometric sensors onboard earth-orbiting satellites to estimate phytoplankton biomass and primary production. The algorithms to estimate these parameters are generally based on global analyses and, where possible, validated or tuned by local data.

Phytoplankton biomass Annual average phytoplankton biomass is estimated according to equation F1.

12 1 j  B= ⋅ Chlj ⋅⋅⋅()C ZA j  [F1] phyto ⋅ ∑ ∑ iChl i i j 12 ∑ Aj i=1  j  j

-2 Where Bphyto = annual average phytoplankton biomass density (gC m ) i = index of month of year (1–12) Aj = area of pixel j j -3 Chl i = Chlorophyll-a concentration in pixel j, month i (gChl-a m ) j (C/Chl) i = carbon-to-chlorophyll-a ratio in pixel j, month i (dimensionless) j Zi = depth of mixed layer in pixel j, month i (m)

The near-surface concentration of chlorophyll-a (chl) is obtained from ocean colour satellite measurements. Such measurement are available for the study region at moderate resolution (1–4 km) for >10 y based on data from SeaWiFS (Murphy et al. 2000) and MODIS-Aqua. Validation studies indicate that the ocean colour measurements of chlorophyll-a concentration are accurate within approximately 35% of the true value in this region (Richardson et al. 2002; Pinkerton et al. 2005). The long-term annual average chlorophyll-a for the study region from MODIS-Aqua data (2002–2012) is shown in Figure F1.

Ecosystem Modelling of the Chatham Rise 143

Figure F1: The long-term annual-average near-surface chlorophyll-a obtained from MODIS- Aqua data (2002–2012). High values are red; low values are blue (range 0.3–21.6 mgChla m -3). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m.

To convert surface values of chlorophyll-a concentration to water column averages, we assumed that phytoplankton were well mixed between the surface and the seasonal thermocline. This depth was identified for each of ~4000 pixels through the study region using a threshold density difference of 0.15 kg m -3 based on climatological data from the CSIRO Atlas of Regional Seas (CARS2000: Dunn & Ridgway 2002), and varied between an average of 37 (summer) and 119 m (winter). Carbon-chlorophyll ratios for marine phytoplankton have been found to vary considerably between 20 to >200 gCg -1Chl-a (Taylor et al. 1997; Lefevre et al. 2003). Data from SOIREE (Boyd 2002) and other experiments in iron-limited waters suggest a seasonally-invariant value of 80-100 gCg -1Chl-a for Subantarctic waters are reasonable. In Subtropical waters, work suggests a seasonal variation in C:Chl values of approximately 50 before the spring bloom, 40 during the spring bloom, and 60 after the bloom (Boyd 2002; Boyd unpublished data). Our estimate of the annual-average, depth-integrated, phytoplankton biomass is hence 2.85 gC m -2.

144 Ecosystem Modelling of the Chatham Rise

Figure F2a: Annual cycle of chlorophyll-a concentration and b: depth-averaged phytoplankton biomass in the study area, estimated as described in the text.

Phytoplankton primary production Net primary production (NPP) is quantified as the annual-average, depth-integrated rate of carbon fixation by phytoplankton net of respiration. NPP can be measured accurately from ships using radioactive carbon ( 14 C) as a tracer, but such shipboard methods cannot adequately map NPP over large areas and on the long-term. Over the last two decades, methods have been developed to estimate NPP by combining satellite observations surface chlorophyll concentration, photosynthetically available radiation (PAR), and sea surface temperature (SST). More than 10 different approaches have been tried and there are significant differences in their results. The original empirical models of NPP (e.g. Platt 1986) have been superseded by simple mechanistic models based on satellite observations of chlorophyll concentration, incident light, and a yield function which incorporates the physiological response of the phytoplankton to light, nutrients, temperature and other environmental variables. SST is often used to parameterise this yield function. A range of such modelling approaches exist (e.g., Platt & Sathyendranath, 1993; Antoine & Morel,

Ecosystem Modelling of the Chatham Rise 145

1996a,b; Behrenfeld & Falkowski, 1997b; Ondrusek et al., 2001), which are distinguished by the degree of integration over depth and irradiance, and the manner in which temperature is used to parameterise the photosynthetic yield function (Behrenfeld & Falkowski, 1997a).

None of the current “state-of-the-art” methods has been adequately validated in New Zealand waters but work in the Chatham Rise region to date suggests that the “Vertically Generalized Production Model” (VGPM) (Behrenfeld & Falkowski 1997a; Behrenfeld et al. 2002) best fits the measurements made at sea (Figure F3). The standard VGPM is a chlorophyll-based model that estimates NPP from chlorophyll-a using a temperature- dependent description of chlorophyll-specific photosynthetic efficiency. For the VGPM, net primary production is a function of chlorophyll, available light, and the photosynthetic efficiency. Incident irradiance (PAR) and SST data were obtained from MODIS-Aqua measurements. Data and algorithms were sourced from the Oregon State University “Ocean Productivity” project (web.science.oregonstate.edu/ocean.productivity). Measurements were available for the period 2002–2013 so is likely to capture the long-term mean conditions. Estimates of NPP were obtained at monthly resolution. The long-term average NPP for the study region is shown in Figure F4 and the annual cycle in Figure F5. Our estimate of annual NPP for the study region is hence 275 gC m -2 y-1.

Campbell et al. (2002) summarised intercomparisons of NPP models and concluded that most models were within a factor of 2 of the in situ 14 C measurements, with algorithms performing best in the Atlantic region, and performing worst in the equatorial Pacific and Southern Oceans. The most difficult conditions for chlorophyll-based models are HNLC, low- temperature, and high chlorophyll conditions (Carr et al. 2006), such as occur south of the Subtropical Front in the study region (Murphy et al. 2000). Research in these waters would help to elucidate the uncertainty in (and improve) the estimates of NPP based on satellite measurements.

Figure F3: In situ measurements of net primary production (NPP) based on 14 C incubation experiments at sea in the Subtropical Front, Subtropical and Subantarctic waters (Bradford- Grieve et al., 1997) and estimated using the Vertically Generalized Production Model based on MODIS-Aqua data (2002–2012). Measurements were made in spring (October) and winter (June- July). Note that NPP values are given as mgC m -2 d-1 rather than gC m -2 y-1.

146 Ecosystem Modelling of the Chatham Rise

Figure F4: Long-term, annual-average, depth-integrated, net primary production based on the Vertically Generalized Production Model using MODIS-Aqua data (2002–2012). High values are red; low values are blue (range 180–440 gC m-2 y-1). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m.

Figure F5: Annual cycle of net primary production (annual-average, depth-integrated) based on the Vertically Generalized Production Model using MODIS-Aqua data (2002–2012).

Phytoplankton P/B Average P/B values (y -1) for each month for the study region as a whole ranged from 41 y-1 (July) to 268 y-1 (January) – Figure F6. The value based on the annual average NPP and phytoplankton biomass was P/B=96 y -1. This is very comparable to production rates in oceanic systems worldwide (Table F1).

Ecosystem Modelling of the Chatham Rise 147

Figure F6: Annual cycle of phytoplankton growth efficiency (P/B, y -1) estimated using seasonal depth-integrated phytoplankton biomass and VGPM-estimates of NPP as described in the text.

Table F1: Annual net productivity rates for phytoplankton from the scientific literature. P/B (y -1) Locality Reference 134 Central Pacific Allain 2005 95 Central Pacific Allain 2005 93 Newfoundland Heymans 2003 166 South Brazil Bight, upwelling system, 20–200 m Gasalla & Rossi 2004 66 Gulf St Lawrence Canada Morissette et al 2003 52 Nova Scotia coast to edge of shelf Bundy 2004 82 Baltic Sea Harvey et al 2003 20 South Benguela; Upwelling coast to shelf break Shannon et al 2003 40 North Benguela; Upwelling coast to shelf break Heymans & Baird 2000 45 Central Chile upwelling coast to 30 Nautical miles Neira & Arancibia 2004 31–76 NE USA: Bering Sea, North Atlantic, Gulf of Maine Link et al 2006 6 East Bering Sea; temperate shelf down to 500m Trites et al 1999 13 SE USA Tropical continental shelf intertidal to 500m Okey & Pugliese 2001 5 USA mid-Atllantic Bight continental shelf Okey 2001 21 Sth Catalan Sea 50 m to 400 m: oligotrophic system Coll et al 2006 248 New Zealand Southern Plateau Bradford-Grieve et al 2003 96 Chatham Rise, New Zealand This study

References Allain, V. (2005). Ecopath model of the pelagic ecosystem of the Western and Central Pacific Ocean. Western and Central Pacific Fisheries Commission: Presented at the 1st Scientific Committee meeting, Noumea, New Caledonia 8- 19 August 2005.

Antoine, D; A Morel. (1996a). Oceanic primary production 1: Adaptation of a spectral light-photosynthesis model in view of application to satellite chlorophyll observations. Global Biogeochemical Cycles 10, 43-55.

148 Ecosystem Modelling of the Chatham Rise

Antoine, D.; Morel, A., (1996b). Oceanic primary production 2: Estimation of global scale from satellite (Coastal Zone Color Scanner) chlorophyll. Global Biogeochem. Cycles, 10, 57-69.

Behrenfeld, M. J.; Falkowski, P., (1997a). A consumer’s guide to phytoplankton primary productivity models. Limnol. Oceanogr., 42(7), 1479-1491.

Behrenfeld, M. J.; Falkowski, P., (1997b). Photosynthetic rates derived from satellite-based chlorophyll concentration. Limnol. Oceanogr., 42(1), 1-20.

Behrenfeld, M.J., Maranon, E., Siegel, D.A., Hooker, S.B., (2002). Photoacclimation and nutrient-based model of light-saturated photosynthesis for quantifying oceanic primary production. Marine Ecology Progress Series 228, 103-117.

Boyd, P.W. (2002). The role of iron in the biogeochemistry of the Southern Ocean and equatorial Pacific: a comparison of in situ iron enrichments. Deep-Sea Research II 49(9–10): 1803–1821.

Boyd, P.; LaRoche, J.; Gall, M.; Frew, R.; McKay, R.M.L. (1999). The role of iron, light and silicate in controlling algal biomass in sub-Antarctic water SE of New Zealand. Journal of Geophysical Research 104(C6): 13395-13408.

Bradford-Grieve, J.M.; Probert, P.K.; Nodder, S.D.; Thompson, D.; Hall, J.;Hanchet, S.; Boyd, P.; Zeldis, J.; Baker, A.N.; Best, H.A.; Broekhuizen, N.; Childerhouse, S.; Clark, M.; Hadfield, M.; Safi, K.; Wilkinson, I. (2003). Pilot trophic model for sub Antarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal Experiment Marine Biology Ecology 289: 223–262.

Bradford-Grieve, J.M., Chang, F.H., Gall,M., Pickmere, S., Richards, F., (1997). Size-fractionated phytoplankton standing stocks and primary production during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand. N. Z. J. Mar. Freshwat. Res., 31, 201-224.

Bundy, A. (2004). Mass balance models of the eastern Scotian Shelf before and after the cod collapse and other ecosystem changes. Can. Tech. Rep. Fish. Aquat. Sci. 2520: xi +140 p + Appendices.

Coll, M.; Palomera, I.; Tudela, S.; Sardá, F. (2006). Trophic flows, ecosystem structure and fishing impact in the South Catalan Sea, Northwestern Mediterranean Sea. Journal of Marine Ecosystems 59: 63-96.

Campbell, J.; Antoine, D.; Armstrong, R.; Arrigo, K; and 19 other authors, (2002). Comparison of algorithms for estimating ocean primary production from surface chlorophyll, temperature, and irradiance. Global Biogeochem. Cycles, 16(3), 1035, doi:10.1029/2002GL015068.

Carr, M.-E., and 37 other authors. (2006). A comparison of global estimates of marine primary production from ocean color. Deep-Sea Res. II, 53: 741–770.

Dunn J.R.; K.R. Ridgway (2002). Mapping ocean properties in regions of complex topography, Deep Sea Research I, 49(3): 591-604.

Ecosystem Modelling of the Chatham Rise 149

Gasalla, M.A.; Rossi-Wongtschowski, C.L.D.B. (2004). Contribution of ecosystem analysis to investigating the effects of changes in fishing strategies in the South Brazil Bight coastal ecosystem. Ecological Modelling, 172: 283–306.

Harvey, C. J.; Cox, S. P.; Essington, T. E.; Hansson, S.; Kitchell, J.F. (2003). An ecosystem model of food web and fisheries interactions in the Baltic Sea. ICES Journal of Marine Science, 60: 939–950.

Heymans, J.J. (ed.). (2003). Ecosystem models of Newfoundland and Southeastern Labrador: Additional information and analyses for 'Back to the Future' FCRR 2003, Vol. 11(5) 79 pp

Heymans, J.J.; Baird, D., (2000). Network analysis of the northern Benguela ecosystem by means of NETWRK and ECOPATH. Ecolological Modelling 131: 97–119.

Lefevre, N.; Taylor, A.H.; Gilbert, F.J.; Geider, R.J. (2003). Modeling carbon to nitrogen and carbon to chlorophyll a ratios in the ocean at low latitudes: evaluation of the role of physiological plasticity. Limnology and Oceanography 48(5): 1796–1807.

Link, J.S.; Griswold, C.A.; Methratta, E.T.; Gunnard, J. (eds.) (2006). Documentation for the Energy Modelling and Analysis eXercise (EMAX). US Department of Commerce. Northeast Fishereis Science Centre Reference Document 06-15. Pp 166.

Morissette, L.; Despatie, S.; Savenkoff, C.; Hammill, M.O.; Bourdages, H.; Chabot, D. (2003). Data gathering and input parameters to construct ecosystem models for the northern Gulf of St. Lawrence (mid-1980s). Canadian Technical Report of Fisheries and Aquatic Sciences 2497. pgs 94.

Murphy, R.J., Pinkerton, M.H., Richardson, K.M., Bradford-Grieve, J.M., Boyd, P.W., (2001). Phytoplankton distribution around New Zealand derived from SeaWiFS data. New Zealand Journal of Marine and Freshwater Research, 35: 343-362.

Neira, S.; Arancibia, H. (2004). Trophic interactions and community structure in the upwelling system off Central Chile (33–398S). Journal of Experimental Marine Biology and Ecology 312: 349–366.

Okey, T.A. (2001). A ‘straw-dog’ Ecopath model of the Middle Atlantic Bight continental; shelf United States. In Guénette, S., Christensen, V., Pauly, D. (eds), Fisheries Impacts on North Atlantic Ecosystems: Models and Analyses. Fisheries Centre Research Reports 9(4): 151-166.

Okey, T.A.; Pugliese, R. (2001). A Preliminary Ecopath Model of the Atlantic Continental Shelf adjacent to the south-eastern United States. In Guénette, S., Christensen, V., Pauly, D. (eds), Fisheries Impacts on North Atlantic Ecosystems: Models and Analyses. Fisheries Centre Research Reports 9(4): 167-181.

150 Ecosystem Modelling of the Chatham Rise

Ondrusek, M.E., Bidigare, R.R., Waters, K., Karl, D.M. (2001). A predictive model for estimating rates of primary production in the subtropical north Pacific Ocean. Deep-Sea Res. II, 48(8-9), 1837-1863.

Pinkerton, M.H.; K.M. Richardson; P.W. Boyd; M.P. Gall; J. Zeldis; M.D. Oliver; R.J. Murphy. (2005). Intercomparison of ocean colour band-ratio algorithms for chlorophyll concentration in the Subtropical Front east of New Zealand. Remote Sensing of Environment 97: 382-402.

Platt, T.; Sathyendranath, S., (1993). Estimators of primary production for interpretation of remotely sensed data on ocean color. J. Geophys. Res., 98: 14561-14567

Platt, T. (1986). Primary production of the ocean water column as a function of surface light intensity: algorithms for remote sensing. Deep Sea Res. 31: 1-11.

Richardson, K.M., Pinkerton, M.H., Image, K., Snelder, T., Boyd, P.W., Gall, M.P., Zeldis, J., Oliver, M.D., Murphy, R.J., (2002). SeaWiFS data from around New Zealand: Validation and an application. COSPAR, World Space Congress, 10-19 October 2002, Houston, USA.

Shannon, L.J.; Moloney, C.L; Jarre, A.; Field, J.D. (2003). Trophic flows in the southern Benguela during the 1980s and 1990s. Journal of Marine Systems 39: 83–116.

Taylor, A.H.; Geider, R.J.; Gilbert, F.J.H. (1997). Seasonal and latitudinal dependencies of phytoplankton carbon-to-chlorophyll a ratios: results of a modelling study. Marine Ecology Progress Series 152: 51–66.

Trites, A.W.; Livingston, P.A..; Mackinson, S.; Vasconcellos, M.C.; Springer, A.M.; Pauly, D. (1999). Ecosystem change and the decline of marine mammals in the Eastern Bering Sea: Testing the ecosystem shift and commercial whaling hyotheses. Fisheries Centre Research Reports 7(1): 106.

Ecosystem Modelling of the Chatham Rise 151

Appendix G Microbial loop

Introduction In this section parameters for the Chatham Rise model are derived for the following 4 lower- trophic level groups in the water column:

1. Heterotrophic nanoplankton (2.0–20 µm): primarily heterotrophic flagellates 2. Microzooplankton (20–200 µm); primarily ciliates. 3. Mesozooplankton (0.2–20 mm); dominated by copepods. 4. Water column bacteria

Heterotrophic flagellates The average annual biomass of heterotrophic flagellates (as carbon) is calculated using data collected in a number of months in the region east of New Zealand in, or close to, the Chatham Rise study area (Bradford-Grieve et al., 1998, 1999; Hall et al. 1999; J.H., unpubl. data). Integrations of biomass are made to 100 m and the assumption is made that there are no heterotrophic flagellates below 100 m if there are no measurements below this depth. Heterotrophic flagellate carbon biomass was calculated using calculated cell volumes (Chang & Gall, 1998). Data summarised in Bradford-Grieve et al. (1999) suggest that heterotrophic flagellate biomass is correlated with phytoplankton net production. We used satellite-based estimates of NPP per month to estimate heterotrophic flagellate biomass per month and hence an annual-average biomass for the study region of 0.28 gC m -2.

Mean daily P/B of heterotrophic flagellates in Subantarctic waters in August and January- February was calculated from dilution grazing experiments (J.H., pers. comm.) and shows little difference in P/B for heterotrophic flagellates between winter and summer (Bradford- Grieve et al. 2003). We assume a constant P/B for heterotrophic flagellates in the study area year round. Grazing and production data from 6 stations, two each in Subtropical, Subantarctic and Subtropical Front waters in spring (October) and winter (June-July) were reported in Bradford-Grieve et al. 1999). These measurements and consistent with P/B values for heterotrophic flagellates in the study region of P/B=200 y-1. Following Bradford- Grieve et al. (2003), we assume that P/Q=0.36 and ecotrophic efficiency of 0.9. Assimilation efficiency, (ingestion – excretion)/ingestion, of heterotrophic flagellates has been measured at 0.84 in low iron conditions (Chase & Price, 1997) and we use U=0.2.

Under some conditions, we know that heterotrophic flagellates consume 4.4% of picophytoplankton biomass and 2.4% of bacterial biomass per day (Safi & Hall, 1999; J.H. unpubl. data) but the proportions in which heterotrophic flagellates consume their food (water column bacteria and phytoplankton) over the course of a year in the study area is not well known. We estimated the diet of heterotrophic flagellates consistent with Bradford-Grieve et al. (1999) as 45% bacteria and 55% phytoplankton.

Ciliates The average annual biomass of ciliates is calculated using data collected in a number of months (Bradford-Grieve et al., 1998; Hall et al. 1999; Julie Hall, NIWA, unpubl. data). Integrations are made to 100 m and the assumption is made that there are no ciliates below 100 m if there are no measurements below this depth. Ciliate carbon biomass was calculated using a factor 0.19 pg C µm-3 (Putt & Stoecker, 1989). Data summarised in Bradford-Grieve

152 Ecosystem Modelling of the Chatham Rise

et al. (1999) suggest that ciliate biomass is correlated with phytoplankton net production. We used satellite-based estimates of NPP per month to estimate ciliate biomass per month and hence an annual-average biomass for the study region of 86 mgC m -2.

Mean daily P/B of ciliates was measured at the equivalent of 88 y -1 (n=5) calculated from dilution grazing experiments (J. H., unpubl. data). These data are from Subantarctic waters in August and January-February; there was little difference in P/B between the two periods, and here we assume a constant P/B for ciliates year round in the study region. Consistent with data reported for the Chatham Rise region (Subtropical, Subantarctic and Subtropical frontal waters) in spring and winter, we estimate P/B for ciliates of 90 y -1. A ciliate production rate of 0.3 d-1 (110 y -1) is near the mean of estimates from a number of studies tabulated by Kiørboe (1998) although growth rates of up to 0.9 d -1 (330 y -1) have been measured (Verity et al., 1993). Also in the subarctic Pacific, ciliate production of 0.10 d -1 (36 y -1) is given by Landry et al. (1993) although this may be too low if predators were not fully excluded from incubations.

We assume that production/consumption is 0.352 (Bradford-Grieve et al., 2003) and ecotrophic efficiency of 0.9. Assimilation efficiency is taken as U=0.2 (Bradford-Grieve et al., 2003). The proportions in which ciliates consume their food (phytoplankton and heterotrophic flagellates) can only be estimated although we know that ciliates consume 70% of the biomass of heterotrophic flagellates and autotrophic biomass per day (J.H., unpubl. data). We estimated the diet of ciliates consistent with Bradford-Grieve et al. (1999) as 60% heterotrophic flagellates and 40% phytoplankton.

Mesozooplankton The average annual biomass (wet weight and as carbon) of mesozooplankton is calculated using data collected in 1993 (Bradford-Grieve et al., 1998), and historical data collated by Bradford (1980). Data summarised in Bradford-Grieve et al. (1999) suggest that mesozooplankton biomass in the Subtropical, Subantarctic and Subtropical Front waters of the Chatham Rise in spring and winter is correlated with phytoplankton net production. We used satellite-based estimates of NPP per month to estimate mesozooplankton biomass per month and hence an annual-average biomass for the study region of 1.3 gC m -2.

The production/biomass ratio for mesozooplankton for low productivity water is about 12 y-1 (Shushkina et al., 1998). This may be compared with P/B of a subtropical copepod Acrocalanus inermis which was measured by Kimmerer (1983) and varied from 26-131 d-1 and 73 y -1 (Vidal, 1980). Baird & Ulanowicz (1989) estimated an average P/B ratio of 135 y -1 over an entire year in Chesapeake Bay, an enclosed coastal system. Bradford-Grieve et al. (2003) estimated P/B=20 y-1 for mesozooplankton in New Zealand Subantarctic waters. . A P/B value of 49 y -1 would be consistent with data reported for the Chatham Rise region (Subtropical, Subantarctic and Subtropical frontal waters) in spring and winter. Compared to data elsewhere in the world (Table G1), this seems high and we estimate P/B for mesozooplankton in the Chatham Rise study region of 30 y -1.

Food intake has been determined experimentally (see Parsons et al., 1984) and ranges from 10-20% of body weight per day for large crustaceans to 40-60% per day for small crustaceans. Paracalanus sp. may eat 1.5 µg N µg body N -1 d-1 (Checkley, 1980) although their specific ingestion of C was 3.6 d -1 when feeding on N-deficient Thalassiosira. For large copepods such as Calanus finmarchicus , Ohman & Runge (1994) showed that, in the lower estuary region of the Gulf of St Lawrence, total food was ingested (diatoms dominant) at the

Ecosystem Modelling of the Chatham Rise 153

rate of 42–48% of body C d -1 and in the open gulf total food was ingested (dominated by aloricate ciliates) at a rate of up to 4% of body C d -1. At all these stations the copepods were laying eggs although the authors consider the possibility that these copepods might not have been in equilibrium with the food supply. The implication appears to be that heterotrophs may be a much better food source that autotrophic food particles. It was assumed that P/Q is 0.35 (as Bradford-Grieve et al., 2003) and ecotrophic efficiency is 0.9. Assimilation of copepods (and the whole mesozooplankton component of the model) is assumed to be 0.7 for animals that are feeding on microzooplankton (Pavlovskaya & Zesenko, 1985).

We assume that the mesozooplankton feed on phytoplankton, microzooplankton, and other mesozooplankton (Bradford-Grieve et al., 1998, Zeldis et al., 2002). We estimate initial proportions of 33% mesozooplankton, 6% ciliates, 33% heterotrophic flagellates and 28% phytoplankton. These diet fractions are consistent with data for the Chatham Rise region reported in Bradford-Grieve et al. (1999).

Table G1: P/B (y -1) for micro- and meso-zooplankton over a range of marine ecosystems from around the world. Micro Meso Location Reference - 27 North British Columbia, Canada Ainsworth et al. 2002, Beattie 2001 100 33 Central Pacific Allain 2005 88 20 NZ Southern Plateau Bradford-Grieve et al. 2003 - 8 Nova Scotia coast to edge of shelf Bundy 2004 1995 to 2000 21 21 South Catalan Sea: coastal 50 m to Coll et al. 2006 400 m: oligotrophic system 90 South Brazil Bight 20 - 200 m Gasalla &Rossi 2004 inshore, wind driven upwelling 214 82 Baltic Sea Harvey et al. 2003 40 40 North Benguela Upwelling coast to Heymans & Baird 2000 shelf 8.4 Newfoundland Heymans 2003 72–135 31–76 NE USA: Bering Sea, North Atlantic, Link et al. 2006 Gulf of Maine 6.8 Gulf St Lawrence Canada Morissette et al. 2003 20 10 Central Chile upwelling coast to 30 Neira & Arancibia 2004 Nautical miles hake, 1992 40 5 USA mid-Atlantic Bight; temperate Okey 2001 continental shelf to 200m 13 SE USA Tropical continental shelf Okey & Pugliese 2001 intertidal to 500m 20 20 South Benguela Upwelling coast to Shannon et al. 2003 shelf 6 East Bering Sea; temperate shelf Trites et al. 1999 down to 500m 90 -200 30 Chatham Rise region This Study

154 Ecosystem Modelling of the Chatham Rise

Water column bacteria We base our estimates of water column bacteria biomass and energetics on Bradford-Grieve et al. (2003). The average annual biomass of bacteria was based on data collected in the study region (Bradford-Grieve et al., 1998, 1999; Smith and Hall, 1997; J.H., unpublished data) using the carbon conversion factor of Fukuda et al. (1998). Data summarised in Bradford-Grieve et al. (1999) suggest that mesozooplankton biomass in the Subtropical, Subantarctic and Subtropical Front waters of the Chatham Rise in spring and winter is correlated with phytoplankton net production. We used satellite-based estimates of NPP per month to estimate mesozooplankton biomass per month and hence an annual-average biomass of water column bacteria for the study region of 1.1 gC m -2.

Production rates of bacteria in the water column are not well known. Data on bacterial biomass and consumption rates of bacteria by heterotrophic flagellates in the Chatham Rise region reported in Bradford-Grieve et al. (1999) suggest production rates by bacteria equivalent to between 22 y -1 (winter) and 160 y -1 (spring). Elsewhere, Shushkina et al.(1998) estimate bacterial P/B to be 92 y-1 based on the analysis of for low productivity waters whereas Sorokin (1999, Table 2.2) gives P/B >182 y -1, which seem too high. Here, we assume an annual average P/B for bacteria in the water column of 60 y -1.

Bacteria in the water column consume detrital and dissolved organic material in the water column. Consumption rates by bacteria are typically quantified via growth efficiency (P/Q) values. Bradford-Grieve et al. (2003) used P/Q=0.23 for bacteria in Subantarctic waters off New Zealand. Lochte et al. (1997) measured values in the Southern Ocean of P/Q=0.30 (0.28–0.31), and P/R=0.43 (0.38–0.44). Growth efficiencies (P/Q) for open ocean bacteria feeding on dissolved organic matter in the Southern Ocean was reported as 0.26–0.30 (Kaehler et al. 1997), which was reported as being consistent with work of Lignell (1990). Here, we use a P/Q for bacteria in the water column of 0.33. All the diet of bacteria is water column detritus (dissolved and particulate combined).

Other information: accumulation, imports, exports, transfers We assume that there is zero net lateral (i.e. “horizontal”) advection of planktonic material into the study region, i.e. that planktonic material entering the study region is close to that leaving the region. There are currently no measurements to test this hypothesis, but the currents are generally low over the study region (<10 cm s -1), suggesting that <6% of water in the study region crosses the boundaries of the region each day, and that local effects will predominate over lateral advective processes.

The model assumes no substantial and consistent change in biomass of planktonic groups from year to year, i.e. we set accumulation to zero.

References Ainsworth, C.; Heymans, S.; Pitcher, T.J.; Vasconcellos, M. (eds) (2002). Ecosystem Models of Northern British Columbia for the Time Periods 2000, 1950, 1900 and 1750 FCRR 2002, Vol. 10(4) 41 pp.

Allain, V. (2005). Ecopath model of the pelagic ecosystem of the Western and Central Pacific Ocean. Western and Central Pacific Fisheries Commission:

Ecosystem Modelling of the Chatham Rise 155

Presented at the 1st Scientific Committee meeting, Noumea, New Caledonia 8- 19 August 2005.

Baird, D., Ulanowicz, R.E. (1989). The seasonal dynamics of the Chesapeake Bay ecosystem. Ecol. Monogr. 59, 329-364.

Beattie, A.I. (2001). A New Model for Evaluating the Optimal Size, Placement and Configuration of Marine Protected Areas. Unpublished Masters thesis. Department of Resource Management and Environmental Science, University of British Columbia, 58pp.

Bradford, J.M., (1980). New Zealand region, zooplankton biomass (0-200 m). N. Z. Oceanogr. Inst. Chart, Misc. Ser. 41.

Bradford-Grieve, J.M., Boyd, P.W., Chang, F.H., Chiswell, S., Hadfield, M., Hall, J.A., James, M.R., Nodder, S.D., Shushkina, E.A., (1999). Pelagic ecosystem structure and functioning in the Subtropcial Front region east of New Zealand in Austral winter and spring 1993. J. Plankton Res. 41(1), 405-428.

Bradford-Grieve, J.M., Probert, P.K., Nodder, S.D., Thompson, D., Hall, J., Hanchet, S., Boyd, P., Zeldis, J., Baker, A.N., Best, H.A., Broekhuizen, N., Childerhouse, S., Clark, M., Hadfield, M., Safi, K. and Wilkinson, I. (2003). Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology 289: 223-262.

Bradford-Grieve, J.M.; Murdoch, R.; James, M.; Oliver, M; McLeod, J. (1998). Mesozooplankton biomass, composition, and potential grazing pressure on phytoplankton during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand. Deep-Sea Research I 45: 1709–1737.

Bundy, A. (2004). Mass balance models of the eastern Scotian Shelf before and after the cod collapse and other ecosystem changes. Canadian Technical Report of Fisheries and Aquatic Sciences No.2520. pgs.193.

Chang, F.H., Gall, M. (1998). Phytoplankton assemblages and photosynthetic pigments during winter and spring in the Subtropical Convergence region near New Zealand. New Zealand Journal of Marine and Freshwater Research 32(4): 515–530Chase, Z.; Price, N.M. (1997). Metabolic consequences of iron deficiency in heterotrophic marine protozoa. Limnol. Oceanogr. 42, 1673-1684.

Checkley, D.M., (1980). Food limitation of egg production by a marine, planktonic copepod in the sea off southern California. Limnol. Oceanogr. 25(6), 991-998.

Coll, M.; Palomera, I.; Tudela, S.; Sardá, F. (2006). Trophic flows, ecosystem structure and fishing impact in the South Catalan Sea, Northwestern Mediterranean Sea. Journal of Marine Ecosystems 59: 63-96.

Fukuda, R., Ogawa, H., Ngata, T., Koike, I., (1998). Direct determination of carbon and nitrogen contents of natural bacterial assemblages in marine environments. Appl. Environ. Microbiol. 64, 3352-3358.

156 Ecosystem Modelling of the Chatham Rise

Gasalla, M.A.; Rossi-Wongtschowski, C.L.D.B. (2004). Contribution of ecosystem analysis to investigating the effects of changes in fishing strategies in the South Brazil Bight coastal ecosystem. Ecological Modelling 172: 283–306

Hall, J.A., James, M.R., Bradford-Grieve, J.M., (1999). Structure and synamics of the pelagic microbial food web of the Subtropical Convergence region east of New Zealand. Aquat. Microb. Ecol. 20, 95-105.

Harvey, C. J.; Cox, S. P.; Essington, T. E.; Hansson, S.; and Kitchell, J. F. (2003). An ecosystem model of food web and fisheries interactions in the Baltic Sea. ICES Journal of Marine Science, 60: 939–950.

Heymans, J.J. (ed.) (2003). Ecosystem models of Newfoundland and Southeastern Labrador: Additional information and analyses for 'Back to the Future' FCRR 2003, Vol. 11(5) 79 pp.

Heymans, J.J.; Baird, D., (2000). Network analysis of the northern Benguela ecosystem by means of NETWRK and ECOPATH. Ecological Modelling 131: 97– 119.

Kaehler, P., Bjornsen, P.K., Lochte, K., Antia, A., (1997). Dissolved organic matter and its utilization by bacteria during spring in the Southern Ocean. Deep-Sea Res. II 44, 341-353.

Kimmerer, W.J., (1983). Direct measurement of the production:biomass ratio of the subtropical calanoid copepod Acrocalanus inermis. J. Plankton Res. 5, 1-14.

Kiørboe, T., (1998). Population regulation and role of mesozooplankton in shaping marine pelagic food webs. Hydrobiologia 363(1-3): 13-27.

Landry, M.R., Gifford, D.J., Kirchmann, D.L., Wheeler, P.A., Monger, B.C., (1993). Direct and indirect effects of grazing by Neocalanus plumchrus on plankton community dynamics in the subarctic Pacific. Prog. Oceanogr. 32, 239-258.

Lignell, R. (1990). Excretion of organic carbon by phytoplankton: its relation to algal biomass, primary productivity, and bacterial secondary production in the Baltic Sea. Marine Ecology Progress Series 68: 85-99.

Link, J.S.; Griswold, C.A.; Methratta, E.T.; Gunnard, J. (eds.) (2006). Documentation for the Energy Modelling and Analysis eXercise (EMAX). US Department of Commerce Northeast Fisheries Science Centre Reference Document 06-15: 166 pp.

Lochte, K.; P.K. Bjørnsen; H. Giesenhagen; A. Weber (1997). Bacterial standing stock andproduction and their relation to phytoplankton in the Southern Ocean. Deep-Sea Research II, 44(1-2): 321-340.

Morissette, L.; Despatie, S.; Savenkoff, C.; Hammill, M.O.; Bourdages, H.; Chabot, D. (2003). Data gathering and input parameters to construct ecosystem models for the northern Gulf of St. Lawrence (mid-1980s). Canadian Technical Report of Fisheries and Aquatic Sciences 2497. pgs 94.

Ecosystem Modelling of the Chatham Rise 157

Neira, S.; Arancibia, H. (2004). Trophic interactions and community structure in the upwelling system off Central Chile (33–398S). Journal of Experimental Marine Biology and Ecology 312: 349–366

Ohman, M.D., Runge, J.A., (1994). Sustained fecundity when phytoplankton resources are in short supply: Omnivory by Calanus finmarchicus in the Gulf of St Lawrence. Limnol. Oceaogr. 39, 21-36.

Okey, T.A. (2001). A ‘straw-dog Ecopath model of the Middle Atlantic Bight continenta; shelf United States. In: Guénette, S., Christensen, V., Pauly, D. (eds), Fisheries Impacts on North Atlantic Ecosystems: Models and Analyses. Fisheries Centre Research Reports 9(4): 151-166.

Okey, T.A.; Pugliese, R. (2001). A Preliminary Ecopath Model of the Atlantic Continental Shelf adjacent to the south-eastern United States. In: Guénette, S., Christensen, V., Pauly, D. (eds), Fisheries Impacts on North Atlantic Ecosystems: Models and Analyses. Fisheries Centre Research Reports 9(4): 167-181.

Parsons, T.R., Takahashi, M., Hargrave, B., (1984). Biological oceanographic processes. Pergamon Press Ltd, Oxford, 332 pp.

Pavlovskaya, T.V., Zesenko, A.J., (1985). Rate of consumption and utilization of natural microzooplankton by mass-occurring copepods of the Indian Ocean. Pol. Arch. Hydrobiol. 32(3-4), 457-471.

Putt, M., Stoecker, D.K., (1989). An experimentally determined carbon: Volume ratio for marine "oligotrichous" ciliates from estuarine and coastal waters. Limnol. Oceanogr. 34, 1097-1103.

Safi, K.A.; Hall, J.A. (1999). Mixotrophic and heterotrophic nanoflagellate grazing in the convergence zone east of New Zealand. Aquat. Microb. Ecol. 20, 83-93.

Shannon, L.J.; Moloney,C.L.; Jarre A .; Field, J.D. (2003). Trophic flows in the southern Benguela during the 1980s and 1990s. Journal of Marine Systems 39: 83–116.

Shushkina, E.A., Vinogradov, M.E., Lebedeva, L.P., (1998). Biotic balance in the ocean and estimation of the organic matter flux from epipelagic zones on the basis of satellite and expeditionary data. Oceanol. 38, 628-635. [translation from Russian]

Smith, R.; Hall, J.A. (1997). Bacterial abundance and production in different water masses around South Island, New Zealand. New Zealand Journal of Marine and Freshwater Research 31(4): 515–524.

Sorokin, Y.I., (1999). Aquatic microbial ecology. Backhuys Publishers, Leiden.

Trites, A.W.; Livingston, P.A..; Mackinson, S.; Vasconcellos, M.C.; Springer, A.M.; Pauly, D. (1999). Ecosystem change and the decline of marine mammals in the Eastern Bering Sea: Testing the ecosystem shift and commercial whaling hyotheses. Fisheries Centre Research Reports 7(1): 106.

158 Ecosystem Modelling of the Chatham Rise

Verity, P.G., Stoecker, D.K., Sieracki, M.E., Nelson, J.R., (1993). Grazing, growth and mortality of microzooplankton during the 1989 North Atlantic spring bloom at 47oN, 18oW. Deep-Sea Res. I 40, 1793-1814.

Vidal, J., (1980). Physioecology of zooplankton I. Effects of phytoplankton concentrations, temperature and body size on the growth of Calanus pacificus and Pseudocalanus sp. Mar. Biol. 56: 111-134.

Zeldis, J., James, M.R., Bradford-Grieve, J.M., Richards, J., (2002). Omnivory by copepods in the New Zealand Subtropical Front Zone: its role in nutrition and export. J. Plankton Res. 24, 9-23.

Ecosystem Modelling of the Chatham Rise 159

Appendix H Benthos and hyperbenthos

Introduction Characteristics of the benthic ecosystem of the Chatham Rise region vary with depth and with location. In particular, many studies have shown differences in benthic community between the northern and southern flanks of the rise (Probert & McKnight 1993; Probert et al. 1996; McKnight & Probert 1997). The benthic ecosystem compartments and linkages used here are based on widely-used energetic models of benthic communities (e.g. Smith 1987, 1989; Christiansen et al. 2001; Gage 2003; Piepenburg et al. 1995; Nodder et al. 2003; Bradford-Grieve et al. 2003). Various sources of food to the benthic ecosystem are distinguished: water-column detritus made up a complex mixture of faecal pellets, dead phytoplankton, zooplankton cells, and “marine snow” (aggregates of different types of detrital particles, bound together loosely by transparent exopolymers: Alldredge & Jackson, 1995); phytoplankton and zooplankton extracted from the water column by epifaunal filter-feeders. Work reported by Gage (2003) shows that concentrated food sources, such as carcasses, quickly attract dense aggregations of a range of scavenging organisms, including fish (rattails, dogfish, and ling) and mobile scavenging megabenthos. For this reason, carcasses are not taken to be part of the water column or benthic detritus, but are assumed to be consumed by the macrobenthos and selected fish species.

Detrital particulate flux to the benthos The annual-average flux of particulate organic matter (“detritus”) to the seabed was estimated to help constrain productivity of the benthos in the Chatham Rise model. We note that vertically migrating organisms can actively transport additional material to (or near to) the seabed and that this material can be used by the benthic and hyperbenthic community. This active bentho-pelagic coupling is handled in the model by the use of diet fractions for benthic and hyperbenthic organisms that include prey species or groups living in the water column. Approaches to model the passive flux of particulate detritus to the sea-floor have been proposed for some time (e.g. Suess 1980; Martin et al. 1987) and using more recent formulations and data (Lutz et al. 2007; Buesseler et al., 2007; Buesseler & Boyd 2009). Here, we use the formulation of Lutz et al. (2007) (equation H1) to estimate the passive, vertical flux of carbon to the sea-bed for each spatial pixel in the Chatham Rise model domain.

−( z − z )   = ⋅d + FzPp()NPP rd exp   p rr  [H1] rld  

Where F(z) = Vertical detrital flux rate (gC m -2 y-1) at depth z (m) below the surface -2 -1 PNPP = annual average phytoplankton net primary production (gC m y ) prd = proportion of NPP which exits the base of the mixed layer as slow- sinking material (dimensionless) prr = proportion of NPP which exits the base of the mixed layer as fast- sinking material (dimensionless). This is also called the vertical “shunt” material zd = depth of the base of the surface mixed layer (m) rld = e-folding remineralization depth scale (m)

160 Ecosystem Modelling of the Chatham Rise

Larger p rd and p rr values indicate the export of a greater fraction of NPP. Larger r ld values indicate the labile fraction of export sinks deeper before regeneration. For simplicity, this equation treats sinking and remineralization rates as constants although these factors vary as particles are transformed as they sink (Lutz et al. 2002, 2007). The combination of (prd + prr ) is the p-ratio, the proportion of the surface NPP that exits the base of the mixed layer. Surface NPP is estimated from satellite data as explained and presented in Appendix F. The coefficients of rld and prr are estimated as equations H2 and H3 (Lutz et al. 2007, Table 2).

=( −) +−++2 rld700exp 0.54 STT VI ( 30 340 ) [H2] =1 ( 2 −++) ( 2 −+ ) [H3] prr2000  2.6 SS VI 4.2 VI 4.8 0.010 TT 0.34 6.0 

Where SVI = Seasonal variation index of NPP T = Annual average sea-surface temperature (°C)

The “seasonal variation index” (Lutz et al. 2007) is the standard deviation of NPP divided by the mean NPP for each pixel, where NPP is calculated from long-term monthly means derived using the VGPM primary production model based on MODIS-Aqua data for 2002– 2012 (Figure H1). The annual sea surface temperature is the long-term mean MODIS-Aqua data, 2002–2012 (Figure H2). Bathymetric depth over the Chatham Rise is shown in Figure H3 (NIWA bathymetric database). For the purposes of this model, we used an annually- constant mixed layer depth of 80 m. Although mesoscale variability (scales of ~100 km) in detrital supply is likely to be significant, and is probably related to the eddy field affecting the distribution of sinking detritus, we do not include lateral advection during sinking into the model as the sinking rates and lateral dispersal rates are not known. By using long-term (10 years) monthly climatologies of primary production, small-scale and short-duration variations in surface primary production will be averaged out.

The combination of (prd + prr ) (the p-ratio) was estimated based on floating sediment trap measurements on the Chatham Rise and north and south of the rise in Subtropical and Subantarctic waters respectively (Nodder & Gall, 1998). Flux measurements were made in spring (October) and winter (June-July). Measured in terms of carbon flux and corrected for small differences between the depth of sediment traps and the base of the mixed layer, particulate detrital flux at the base of the mixed layer (p-ratio) was between 0.5 and 3.4% (mean value of 1.9%) of surface NPP. Surface NPP was measured at the same time as the sediment flux deployments using shipboard 14 C incubations (Nodder & Gall, 1998; Bradford- Grieve et al. 1999). These local measurements of the p-ratio are much lower (about one tenth) than those estimated using the regressions of Lutz et al. (2007) based on global data compilations. Data and analyses in Lutz et al. (2007) lead to estimated p-ratios for the Chatham Rise region of 11-19% (mean 16%).

Local data on the sediment flux and NPP in the Chatham Rise region suggest that the p-ratio is negatively correlated with NPP (Figure H4). Taking the asymptotic p-ratio at high NPP values as 0.5%, we fitted an exponential relationship between the p-ratio and NPP. We used the relationship derived from just the Subtropical Front data to predict the p-ratio for each pixel in the Chatham Rise in each month. These are summed to estimate the annual flux of particulate detritus to the seafloor (Figure H5). The annual flux averaged over the study region is estimated to be 2.3 gC m -2 y-1. The range of annual flux measurements over the

Ecosystem Modelling of the Chatham Rise 161

study area was 1.3-3.0 gC m -2 y-1. We estimate that this flux is equivalent to about 0.8% of total annual NPP by phytoplankton. Based on other estimates in the model, particulate detrital flux to the benthos represents about 1% of the flow of carbon into detritus in the water column.

This estimate is consistent with longer-term, deep water flux measurements made north and south of the Chatham Rise. Vertical downward particulate carbon flux on the north and south flanks of the Chatham Rise was measured in three seasons at two depths (300 and 1000 m) in water depths of c.1500 m (Nodder & Northcote 2001). The flux at 1000 m depth was always greater than the flux at 300 m, by a factor of between 1.1 and 4. The elevation of particulate carbon flux with depth is well-reported phenomenon and has been attributed to a number of factors, including local resuspension of detritus from the flanks of the Chatham Rise as documented previously (Nodder 1997; Nodder & Alexander 1998). The flux at 300 m is likely to be a reasonable estimator of the net input of organic detrital carbon to the benthos from the upper water column, since pulses of flux at 300 m seem to be correlated with blooms in the upper ocean observed by ocean colour satellite data (Nodder, unpublished data). Rates of flux were estimated to be 2.1-5.8 gC m -2 y-1. Longer-term measurements in deeper waters to the north and south of the Chatham Rise (Nodder et al. 2005) suggest rates of annual detrital flux to the seabed of 0.79 gC m -2 y-1 (Subtropical water) and 0.16 gC m -2 y-1 (Subantarctic water). The higher flux rates on the Chatham Rise are due to its shallower depth than these deepwater sites and hence lower remineralization rates.

Figure H1: Seasonal variation index based on the Vertically Generalized Production Model of NPP using MODIS-Aqua data (2002–2012). High values are red; low values are blue (range 1.5– 3.0). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m.

162 Ecosystem Modelling of the Chatham Rise

Figure H2: Long-term annual average sea-surface temperature over the Chatham Rise obtained from MODIS-Aqua data (2002–2012). High values are red; low values are blue (range 10.5°C–15.3°C). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m.

Figure H3: Depth of water over the Chatham Rise. High values are red; low values are blue (range 0–5100 m). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m.

Ecosystem Modelling of the Chatham Rise 163

Figure H4: P-ratio (proportion of the surface net primary production, NPP) that is exported vertically from the surface mixed layer as sedimenting particulate detritus. Points are floating sediment-trap measurements just below the base of the mixed layer in spring and winter (Nodder & Gall 1998). Surface NPP was measured by shipboard 14 C incubations (Nodder & Gall 1998; Bradford-Grieve et al. 1999). The fitted lines assume an asymptotic p-ratio at high NPP of 0.5%, and are: y = 0.0355 exp(-0.00356 NPP)+0.005 (all data); y = 0.0562 exp(-0.00306 NPP)+0.005 (Subtropical Front data only).

Figure H5: Estimated long-term flux of carbon to the sea-bed as sedimenting particulate detrital material, based on the flux model of Lutz et al. (2007) tuned to local sediment trap measurements on the Chatham Rise (Nodder & Northcote 2001). High values are red; low values are blue (range 0.73–2.92 gC m -2 y-1). The trophic model area and prospecting licence area are shown as thick black outlines. Depth contours (thin black lines) are plotted at 500, 1000, 2000 and 3000 m.

Detrital Accumulation Long-term (i.e. >decadal) benthic biomass accumulation on the Chatham Rise at depths shallower than 1500 m was estimated as Nodder et al. (2003) based on data from E. Sikes (Rutgers University, USA). The measurements indicate that, at some times of the year, carbon accumulated at the rate of 2.7–12 gC m -2 y-1, increasing with depth. However, geological measurements in the area suggest that net accumulation over long time periods

164 Ecosystem Modelling of the Chatham Rise

(1000 years) at depths greater than about 1500 m is negligible (H. Neil and L. Carter, NIWA). In this study we assume that accumulation that occurs in some seasons is balanced by a net consumption of benthic carbon at other times of the year, so that long-term average annual accumulation rates of organic carbon are small, here set to 1 gC m -2 y-1. This includes the input from calcified exoskeletons/shells of organisms living over the rise. Total organic matter content of sediments ranged from about 1% to 5% of total sediment weight on the Chatham Rise, with mean of 2.6% (Nodder et al. 2011). Taking dry bulk density of sediment at as 1 g cm -3, and carbon as 50% of total organic matter (TOM), this is equivalent to an accumulation rate of approximately 0.1 mm y -1.

Benthic Community Carbon Budget Sediment Community Oxygen Consumption (SCOC) across the centre of the Chatham Rise was measured by Nodder et al. (2003) and further measurements were made on OS20-20 (Nodder et al. 2011). Carbon remineralization by the benthic community was calculated by assuming a respiration quotient of 0.85 for mixed carbohydrate and lipid components (Hargrave 1973; Smith 1987, 1989). The autumn, spring and summer seasonal measurements were used to estimate an annual average value of benthic infaunal community carbon remineralization rate, and this was observed to follow approximately a power-law decrease with depth, from >12 gCm -2y-1 at 450 m to 4 gCm -2y-1 at 2500 m (R 2=0.39, n=9). Values were progressively reduced by 10% per 500 m to account for the likely elevation of remineralisation rates measured by the shipboard incubations relative to in situ measurements due to pressure and temperature related effects on the translocated organisms (Jahnke et al. 1989; Glud et al. 1994; Witbaard et al. 2000). This relationship was used to estimate the annual mean carbon remineralization rate for the study region as a whole, giving 6.8 gCm -2y-1 as the total infaunal community respiration. Studies suggest that the megabenthos may contribute 10–30% to total benthic community respiration (Piepenburg et al. 1995). If we assume that the respiration of epifaunal macrobenthos is 0–20% of the total infaunal respiration, annual average, total benthic community respiration would be estimated to be in the range 3.8–27.1 gCm -2y-1. Our estimate of the annual average particulate detrital flux to the benthos of 1.3–3.0 gCm -2y-1 is less than that required to supply the needs of the benthic community based on SCOC and the long term burial of carbon. Such a shortfall has been observed in other studies (e.g. Christiansen et al. 2001; Nodder et al. 2003), one potential explanation being that benthic organisms (primarily the benthic bacteria) are able to use dissolved organic carbon from water permeating the sediments. The active coupling between the water column and benthos (as a result of vertically migrating hyperbenthic biota like decapods) is also likely to augment passively sinking detritus as a food source in the benthic ecosystem.

Benthic bacteria We used measurements of benthic bacterial biomass and production at 10 stations across the Chatham Rise (Nodder et al. 2003) close to 180°E. Most measurements were made of the top 3 cm of sediment only. Data from 8 summer stations showed that bacterial production in each 1 cm layer of sediment decreased with sediment depth, so that bacterial production integrated to 9 cm depth was 1.6 times the production integrated between 0–3 cm. We assume that production below 9 cm depth is negligible, and use this factor to estimate bacteria production and viable bacterial biomass for the whole depth of sediment, from measurements between 0–3 cm. Bacterial biomass and productivity data measured by

Ecosystem Modelling of the Chatham Rise 165

Nodder et al. (2003) are very variable by season and depth, perhaps because of variability in detrital supply to the benthos from the water column affected by the production in the surface waters of the STF. Bacteria production in winter was not measured and was assumed to be 60% of the average for the other seasons, following average surface chlorophyll concentrations. Seasonal variation in total bacterial biomass was taken to follow bacterial production.

Bacterial biomass showed no systematic variation with depth (R 2<0.02, n=10). The annual mean benthic bacterial biomass was 1.3 gC m-2, with a standard deviation of 1.0 gC m-2. The biomass is comparable with that estimated using the regression of Deming & Yager (1992) of about 1.5 g C m -2 to a sediment depth of 15 cm. Probert (1986) found bacterial biomass of 1.0 gCm -2 for Shelf waters (<200 m deep) off west coast New Zealand. Note that we have no measurements of the proportion of the total bacterial biomass measured by Nodder et al. (2003) that is viable.

Annually averaged bacteria production decreased systematically with depth (R 2=0.55, n=10), consistent with previous work (e.g. Alongi 1990). Bacterial production integrated over the study region based on this regression result (as described earlier) was 0.64 gC m-2 y-1. We assume a nominal uncertainty in this estimate of production of a factor of 2 i.e. we take productivity to lie in the range 0.32–1.3 gC m-2 y-1. These values are considerably lower than the average bacterial production of 16.9 gC m-2 y-1 reported by Kemp (1994) for slope sediments (<2000 m), and by Alongi (1990) for 600 m depth of 34.7 gC m -2 y-1. The bacterial biomass and production values measured by Nodder et al. (2003) suggest mean P/B of 0.5 y-1 which seems low; although there is considerable variation in measurements of annual P/B ratios of benthic bacteria in the literature, most studies show values greater than this. For example, Poremba and Hoppe (1995) found values of 10.9 y -1 in the Celtic Sea (135–1680 m). Alongi (1990) measured specific growth rates for benthic bacteria at bathyal and abyssal stations which vary widely from 0.37 – 43.8 y -1. Sorokin (1999) gives values of P/B between 7.3–14.6 y -1 off Japan. Earlier work (Ankar 1977; Gerlach 1978; Sorokin 1981; Feller & Warwick 1988) suggest that annual P/B ratios of benthic bacteria are likely to lie between about 20 and 150 y -1, with 55 y -1 as an average value. These may be higher than estimated based on Chatham Rise data perhaps because a proportion of the benthic bacteria on the Chatham Rise are not viable, so that P/B values for the viable bacteria are higher. Testing of this awaits further data. We assume a production rate for bacteria in the sediment on the Chatham Rise of P/B=1 y-1. A benthic bacterial growth efficiency (P/Q) of 0.3 is plausible (Kirchman, 2000; Pomeroy 1979) implying Q/B of 17 y-1.

Meiobenthos Meiofaunal biomass (infauna 63 µm–0.5 mm) on the Chatham Rise has been measured on a series of voyages by Scott Nodder (NIWA), and was also measured on the survey of the Chatham Rise as part of the Ocean-Survey 20-20 project. Meiofaunal biomass (infauna 63 µm–0.5 mm) on the Chatham Rise was dominated by nematodes (>80% of individuals) and was measured in three seasons, at depths between 350 and 2600 m by Nodder et al. (2003). The meiofaunal biomass values were within the envelope reported for a variety of temperate and tropical continental margins around the world (Soltwedel 2000, figure 2; Feller and Warwick, 1988). Annual average meiofaunal biomass on the Chatham Rise integrated to 5 cm depth of sediments decreased systematically with water depth as in these previous studies. Meifaunal wet weight was converted to carbon assuming that carbon makes up

166 Ecosystem Modelling of the Chatham Rise

~10% wet-weight of meiobenthos (Feller & Warwick 1988; Soltwedel 2000). A depth-biomass regression was determined by least-squares in log biomass space (Figure H6). We hence estimate total meiofaunal biomass on the Chatham Rise was 270,000 tWW, equivalent to a mean meiofaunal density of 0.12 gCm -2.

Annual P/B ratios of meiofauna vary considerably, between about 2.5 and 15, but 10 y -1 is often taken as an average value (Feller & Warwick, 1988; Probert 1986) and is used here. Annual P/Q was assumed to be 0.31 (Pomeroy 1979; Bradford-Grieve et al. 2003), though a P/Q of between 0.1 and 0.3 y -1 was suggested by Probert (1986). These lead to a consumption rate of 32 y -1. The prime source of food for the meiobenthos is assumed to be bacteria with some cannibalistic contribution from other meiobenthos. Ecotrophic efficiency is not known but is assumed to be 0.95. Accumulation and export are set to zero. Unassimilated consumption is assumed to be 0.2.

Figure H6: Measured meiofaunal biomass on the Chatham Rise measured by Nodder (NIWA, unpublished data) and by Ocean Survey 20-20 (TAN0705) Objective 2. The least squares regression is based on all data combined.

Megabenthos Benthic megafauna are defined operationally as organisms living on or near the seabed that can be observed in near-bottom video or camera images. This approximates to individuals greater than about 20 mm in size (Bowden, 2011). For the purposes of the trophic modelling, we exclude fishes from this group. This group includes large mobile hyperbenthic invertebrates (e.g. decapods), sessile invertebrates (e.g. corals, sponges, crinoids), echinoderms, polychaetes, molluscs, and bottom-dwelling cephalopods. Megabenthic decapoda on the Chatham Rise include squat lobsters (e.g. Munida gracilis); scampi (Metanephrops challengeri ); shrimps (e.g. Pasiphaea barnardi , Oplophorus novaezeelandiae, Notopandalus magnoculus and Sergestes arcticus ); crabs (e.g. Pycnoplax victoriensis ); hermit crabs (e.g. Sympagurus dimorphus ); and isopods (e.g. Brucerolis sp.).

Ecosystem Modelling of the Chatham Rise 167

Biomass from DTIS We base our estimate of benthic megafauna on the Chatham Rise on data collected on the Ocean-Survey 20-20 project. During 2006 and 2007, this project carried out voyages to the Chatham Rise and the Challenger Plateau to quantify and characterise seabed habitats to depths of 1500 m. To characterise assemblages across a range of organism sizes and spatial scales, samples were collected using several gear types: coarse mesh ‘seamounts’ epibenthic sled and beam trawl (sampling mega-epifauna); multicorer (meiofauna); fine mesh ‘Brenke’ epibenthic sled (macro-epifauna and hyperbenthic fauna); the still image camera of NIWA’s Deep Towed Imaging System (DTIS) (mega- and macro-epifauna, bioturbation, and substrate types), and the video camera of DTIS (mega-epifauna and substrate types). Details are given in Bowden (2011). In particular, DTIS video transects were used to provide an estimate of the abundance density (number of individuals per 1500 m 2) of megabenthos at 108 sites across the Chatham Rise (Figure H8, Bowden 2011). In the future, data from the TAN1116 voyage could be usefully integrated with that from Ocean-Survey 20-20 project to better estimate biomass of megabenthos on the Chatham Rise, but these data were not available at the time of writing. We also note that the mid-Chatham rise Benthic Protection Area is poorly represented in terms of DTIS information used to estimate megafaunal biomass in the trophic model.

In order to make reliable and consistent identifications from DTIS images, a reference library of identification images was generated. Specialist taxonomists for each group then assigned identifications for each taxon at the lowest practicable taxonomic resolutions. Because these identifications were across a range of taxonomic levels, including, in some instances, just numbered putative species (e.g., “Corallimorpharia 1”), they are referred to here as operational taxonomic units (OTUs). There were 319 taxonomic units observed in the Chatham Rise DTIS video dataset used here. For the purpose of the trophic modelling, these 319 taxonomic units were mapped onto 22 functional groups (Table H1), neglecting algae, salps, and vertebrates (fish) seen in the DTIS images. Where practicable, physical samples of the major taxa in each megabenthos group were measured and weighed onboard during the OS20-20 voyages. These data were used to provide a mean wet weight for each of the functional groups. Factors to account for the proportion of the blotted wet weight of organisms due to calcified shell/exoskeleton are also shown in Table H1, and the reference for these estimates.

In order to extrapolate these point measurements of megabenthic density to the study area, we used the biogenic habitat maps developed from the OS2020 voyages data (Hewitt et al. 2011) under the assumption that mean densities of organisms measured in each biogenic habitat class are representative of biomass in that habitat. Objective 10 of the OS2020 project determined the biotic habitats on the seabed across the Challenger Plateau and Chatham Rise (Hewitt et al. 2011). Biotic habitats represent groups of taxa that occur at one or more sites. A number of taxa or a single taxon can define a biotic habitat. Sites within a biotic habitat may have faunal communities that are very similar to one another, or they may be quite different, making variable community composition a diagnostic of that biotic habitat. The 19 biological groups identified across sampling transects in the Chatham-Challenger project were confirmed as spatially contiguous biotic habitats, associated with specific environmental factors or found in specific locations. Of the 19 groups, nine formed major biotic habitats; four of which were unique to the Chatham Rise. The remaining ten groups formed minor biotic habitats, six of which were also unique to the Chatham Rise. Biotic

168 Ecosystem Modelling of the Chatham Rise

habitats are often associated with certain environmental characteristics (e.g., depth, slope) that make extended mapping possible through the use of these as surrogate variables. Hewitt et al. (2011) used depth, roughness, tidal currents, salinity and sea surface productivity as surrogate variables to produce maps of the biotic habitats across the Chatham Rise (Figure H8). The areas for which we have biogenic habitat cover 93% of the total model area. Numerical densities of functional groups are shown in Table H2.

Total abundance of each functional group over the study area was hence calculated. This was converted to blotted wet weight biomass using the mean measured weights for each functional group. The wet masses of several megabenthic taxa are greatly biased by water content, massive inorganic outer shells and/or inorganic carbon-rich (CaCO 3) skeletal material, and variable amounts of organic carbon as a percentage of wet and dry weights (Rowe 1983). Values of blotted biomass wet weight were converted to shell-free wet weight using the values in Table H1. Carbon biomass was calculated based on carbon:WW ratios for each functional group, also shown in Table H1 (Riccirdi & Bourget 1998; Pinkerton 2011). Each of the 22 functional groups was assigned to one of 8 trophic model groups (Table H3). Energetic and other parameters for these groups were estimated based on information given in Pinkerton (2011, Appendix 4). Biomass of octopods observed by DTIS was very small compared to biomass of water column squids and it is likely that the biomass of octopods is poorly quantified using DTIS data alone. We combined the estimate of octopod biomass into the water column cephalopod trophic group.

Biomass from beam trawl Arthropods appear often in the diet of many commercially-important fish species (e.g. Connell et al., 2010; Dunn et al. 2009) and are likely to be relatively common over the Chatham Rise. Based on their presence in the diet of other organisms on the Chatham Rise (fish and squid) and the consumption rates of these predators, we would estimate an average biomass density of arthropods of 0.20 gC m -2. Abundance of natant decapods was measured over the Chatham Rise on the TAN1116 “Fisheries Oceanography II” voyage in November 2011 using the beam trawl (Nodder, 2011; Figure H9). The total arthropod biomass based on consumption estimates is 24 times higher than the biomass of natant decapods estimated from the TAN1116 beam trawl data and 350 times higher than the biomass of decapods based on DTIS data from OS20-20. Some arthropods (e.g. shrimps, prawns, burrowing crabs) are likely to be poorly sampled by many types of gear, including underwater video and beam trawls, because the species live are above the sea-bed or buried in sediments. The selectivity of the beam trawl for decapods is likely to be low but is uncertain because the distribution of the animals through the water column is poorly understood. Large isopods (such as Brucerolis sp.) also seem to be underrepresented in DTIS observations relative to decapods (David Bowden, pers. com.). Biomass of infaunal arthropods, including crabs (e.g. Pycnoplax victoriensis ) and hermit crabs (e.g. Sympagurus dimorphus ) is also not known. Biomass density was hence estimated according to predator demand.

Ecosystem Modelling of the Chatham Rise 169

Production Production to biomass ratios for megafauna on the Chatham Rise were estimated by three methods and the results averaged. First, data on megabenthic productivity was obtained from the modelling work of Jarre-Teichmann et al. (1997). These were adjusted upwards to account for the difference in bottom temperature between the study area of Jarre-Teichmann et al. (1997) and the Chatham Rise according to Brown et al. (2004). Second, estimates of the productivity of a range of benthic megafauna were calculated by Pinkerton (2011). These were adjusted down according to Brown et al. (2004) to account for the differences in bottom temperature between the two systems. Third, a size-based (allometric) regression was used (similar to Banse & Mosher, 1981) to estimate P/B based on body size (organic wet weight). The form used was P/B=1.31W -0.25 , where W=individual animal weight (gWW ind -1) based on Pinkerton (2011) adjusted for water temperature. Values of P/B for each functional group were combined according to their relative biomass and are shown in Table H3.

Consumption and other parameters Consumption rates for benthic megafauna were estimated assuming that P/Q (growth efficiency) followed values estimated for the same functional groups in Pinkerton (2011) based largely on the review in Lundquist & Pinkerton (2008). Growth efficiencies for corals, encrusting invertebrates, ophiuroids, asteroids and pycnogonids are estimated to be P/Q=0.25. We use literature estimates of trophic parameters for holothuroids in temperate systems to estimate P/Q= 0.18 (Okey et al. 2004). Shelled groups also have P/Q=0.18 and echinoids are estimated to have P/Q=0.15 (Lundquist & Pinkerton, 2008). Diets are not well known in the study area, but are estimated assuming similar feeding to elsewhere in the world by similar functional groups. Diet of arthropods on the Chatham Rise was based on unpublished data on gut contents using decapod samples from the TAN1116 voyage (Jeff Forman, pers. comm.) Unassimilated consumption for all groups of megabenthos was set to 0.3 (Jarre-Teichmann et al., 1997).

Organic carbon used to build inorganic-carbon in the shell or exoskeleton of organisms constitutes an export of carbon from the system. The inorganic carbon may be shed periodically (e.g., moulted exoskeleton of decapods), or accumulated while the organism is alive (e.g., shells get larger as the organism grows). Either way, this increase in the mass of inorganic carbon over time due to metabolic processes of the animal represents an export of organic carbon from the system. This export fraction was assumed to follow data for similar functional groups as given in Pinkerton (2011) (Appendix 4: Benthic invertebrates).

170 Ecosystem Modelling of the Chatham Rise

Figure H7: Deep Towed Imaging System (DTIS) sites sampled during the 2007 Ocean Survey 20/20 voyages to the Chatham Rise. At each site, at least one photographic transect with a duration of more than 1 hour was carried out.

Figure H8: Spatial pattern of biotic habitats across the Chatham Rise (Hewitt et al. 2011). Intensity of colours is used to indicate 3 levels of certainty: DTIS sampled positions (filled circles) are shown in intense colours indicating highest certainty; areas interpolated based on distinctive environmental characteristics are shown in faded colours indicating lower certainty, and white areas are those for which we do not have enough information to predict biotic habitats. Stars represent sites designated as minor habitats.

Ecosystem Modelling of the Chatham Rise 171

Figure H9: Measured density (individuals 1000 m -2) of natant decapod crustaceans on the Chatham Rise from TAN1116 voyage (November 2011). Species shown are: Campylonotus rathbunae (top left), Notopandalus magnoculus (top right), Pasiphaea sp. (lower left), and Sergestes sp. (lower right). Data are from beam trawl samples only (Nodder, 2011).

172 Ecosystem Modelling of the Chatham Rise

Table H1: Functional groups used to estimate biomass from OS20-20 data. Factors used to correct for the proportion of the wet weight (WW) of calcified shell/exoskeleton are also shown, and the reference for these estimates. DW=dry weight. Std. Calcified shell/exoskeleton proportions C:WW ratio deviation DW/WW % Reference Mean of for non- individual individual Proportion calcified Functional mass mass DW calcified tissue %WW group Description gWW ind -1 gWW ind -1 (%) 1 (%) 1 calcified Reference All hard corals, includes Antipatharia, Gorgonacea, Riccirdi & Bourget 1998; Hard_corals Scleractinia 13.79 No data 0 0 95 This study 5.7 Galeron et al. 2000 All soft corals and anenomes, including Riccirdi & Bourget 1998; Soft_corals medusae 3.59 3.85 0 0 0 This study 6.3 Vinogradov 1953 Riccirdi & Bourget 1998; Ascidiacea Sea squirts 3.00 4.08 0 0 0 This study 1.4 Galeron et al. 2000 Riccirdi & Bourget 1998; Asteroidea Sea-stars 23.81 31.15 60 33 33 DB pers. com. 8.7 Galeron et al. 2000 Wright & Hetsel, 1985; Hickman & Illingworth Riccirdi & Bourget 1998; Bivalvia Bivalves 3.35 6.11 0 0 73 1980 8.7 Galeron et al. 2000 Brachiopoda Brachiopoda 1.55 1.24 0 0 90 This study 3.0 Riccirdi & Bourget 1998; Riccirdi & Bourget 1998; Bryozoa Bryozoa 2.48 3.90 0 0 50 This study 6.4 Vinogradov 1953 Cephalopoda Cephalopoda 20.64 23.62 0 0 0 This study 10.3 Riccirdi & Bourget 1998; Crinoidea Sea lilies 0.65 0.36 73 43 54 DB pers. com. 3.5 Riccirdi & Bourget 1998; Prawns, shrimps, squat Riccirdi & Bourget 1998; Decapoda lobsters, crabs 6.90 24.88 0 0 0 This study 9.2 Galeron et al. 2000 Echinoidea Echinoidea 32.11 41.72 78 34 54 Lebrato et al 2010 2.8 Riccirdi & Bourget 1998; Foraminifera Foraminifera (giant) 1.12 3.12 0 0 50 This study 5.8 Mean gastropods, bivalves Tokeshi et al. 2000; Pinkerton 2011; Gastropoda Includes tusk shell 6.31 10.68 72 20 34 Gambi & Bussotti 1999 6.7 Galeron et al. 2000 Hemichordata Acorn worms 2.99 5.78 0 0 0 This study 5.2 Riccirdi & Bourget 1998; Riccirdi & Bourget 1998; Holothuroidea Sea cucumbers 20.01 48.03 3 19 1 DB pers. com. 4.7 Brey 2005 Riccirdi & Bourget 1998; Hydrozoa Hydrozoa 3.43 6.95 0 0 0 This study 8.3 Galeron et al. 2000 Isopoda Isopods 1.35 1.17 0 0 0 This study 8.7 Riccirdi & Bourget 1998; Ophiuroidea Brittlestars 1.91 2.68 78 47 62 DB pers. com. 4.7 Riccirdi & Bourget 1998;

Ecosystem Modelling of the Chatham Rise 173

Galeron et al. 2000 Riccirdi & Bourget 1998; Pennatulacea Sea pens 12.96 28.90 0 0 0 This study 5.7 Galeron et al. 2000 Polychaeta, Echiura, Riccirdi & Bourget 1998; Worms Annelida, Nermatean 2.99 5.78 0 0 0 This study 8.2 Galeron et al. 2000 Riccirdi & Bourget 1998; Porifera Sponges 48.38 100.85 0 0 0 This study 5.3 Dayton et al. 1974 Pycnogonida Sea spiders 1.52 1.05 0 0 0 DB pers. com. 10.4 Galeron et al. 2000

174 Ecosystem Modelling of the Chatham Rise

Table H2: Densities of functional groups (individuals per 1500 m 2) in each biotic habitat. Areas of biotic habitats are also shown and their relative proportions.

Biogenic habitat B1 B2 B4 B5 B6 B7 B8 B9 m10 m14 Area (km 2) 15448 16737 10785 74357 22425 20568 6812 37848 2895 174 Proportion (%) 7.4 8.0 5.2 35.7 10.8 9.9 3.3 18.2 1.4 0.1

Abundance of functional groups (ind 1500 m -2) Hard_corals 0.19 3.08 1.93 1.14 0.07 0.24 0.26 2.37 0.68 0.08 Soft_corals 0.68 0.16 0.26 1.31 0.18 0.26 0.17 5.94 211.32 2 0.40 Ascidiacea 0.00 0.00 0.03 0.20 0.00 2.35 0.05 0.00 0.00 0.00 Asteroidea 0.15 0.37 0.46 0.68 2.14 0.27 0.15 0.16 0.10 0.73 Bivalvia 0.00 0.00 0.00 0.09 0.30 0.22 0.08 0.09 0.00 0.00 Brachiopoda 0.00 0.00 0.00 0.00 0.00 0.34 0.00 0.00 0.00 0.00 Bryozoa 0.08 3.67 0.12 0.50 0.00 0.08 1.37 2.91 0.96 0.25 Cephalopoda 0.00 0.03 0.03 0.01 0.00 0.03 0.05 0.01 0.00 0.00 Crinoidea 0.00 0.02 0.29 0.02 0.00 0.00 0.00 0.04 0.00 0.00 Decapoda 0.03 0.41 0.26 1.97 1.28 1.56 0.87 1.15 1.20 0.23 Echinoidea 0.18 1.77 12.57 1.77 7.42 2.34 1.05 2.52 0.02 0.07 Foraminifera 0.00 0.45 1.23 16.02 0.00 1.12 0.11 9.62 0.30 0.00 Gastropoda 0.42 0.13 1.01 0.73 0.45 0.49 0.36 2.63 0.28 0.17 Hemichordata 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 Holothuroidea 0.30 1.17 0.22 0.06 0.12 0.19 0.35 0.07 0.03 2.42 Hydrozoa 0.66 10.07 0.66 8.51 3.49 0.11 0.60 0.20 0.00 0.00 Isopoda 0.00 0.00 0.00 0.07 0.06 0.03 0.00 0.25 0.61 0.00 Ophiuroidea 2229.91 1 0.34 0.65 0.22 0.14 0.57 0.05 1.58 0.00 24.83 Pennatulacea 0.37 11.61 0.06 0.72 0.18 0.78 0.36 3.12 0.15 1.82 Worms 0.02 0.07 0.61 8.84 0.50 0.20 0.14 0.12 0.00 0.28 Porifera 4.35 0.01 0.81 0.11 0.23 0.19 0.06 0.23 0.42 7.62 Pycnogonida 0.61 0.00 0.44 0.00 0.00 0.00 0.20 0.14 0.00 0.00 1 Very high abundances (4000-30,000 individuals 1500 m -2) of the ophiuroid Ophiomusium lymani were found at all 6 stations in biogenic habitat B1. 2 Very high abundances of “Anemone uni 7” were found at two stations in biogenic habitats B9 and m10.

Ecosystem Modelling of the Chatham Rise 175

Table H3: Groups of benthic megafauna used in the Chatham Rise trophic model. 1Contribution of the functional group to the total biomass of the trophic model group.

Trophic model B P/B Q/B 1 -2 -1 -1 X/P group Functional group and contribution to biomass (%) EE mgC m y y P/Q

Corals Hard_corals (2%), Soft_corals (42%), Pennatulacea (56%) 0.75 1.68 0.82 3.3 0.25 0.52 Ascidiacea (<1%), Bryozoa (3%), Crinoidea (<1%), Hydrozoa Encrusting_inverts (47%), Porifera (49%) 0.95 1.75 0.46 1.8 0.25 0.26 Seastars & brittlestars Asteroidea (13%), Ophiuroidea (87%) 0.95 4.34 0.70 2.8 0.25 0 Echinoids Echinoidea (100%) 0.95 0.81 0.35 2.4 0.15 0.22 Holothurians Holothuroidea (100%) 0.10 0.13 0.35 2.0 0.18 0 Arthropods Decapoda (99%), Isopoda (1%), Pycnogonida (1%) 0.95 0.56 1.40 5.6 0.25 0 Large_benthic_worms Worms (99%), Hemichordata (<1%) 0.95 0.54 2.78 11.1 0.25 0 Bivalvia (2%), Bra chiopoda (<1%), Foraminifera (48%), Shelled_megabenthos Gastropoda (51%) 0.95 0.35 1.33 7.2 0.18 0.42

176 Ecosystem Modelling of the Chatham Rise

Macrobenthos This group includes all benthic epifauna between 0.5 and 20 mm in size which are generally too small to be seen in underwater video or camera data. Macrofauna tend to be ecologically and taxonomically diverse. Benthic macrofauna may be epifauna (on or above the surface of the sediment) or infauna (burrowing into the sediment). Epifauna are hard to sample, and the Brenke sled is the only way at present of sampling these fauna. Infaunal macrobenthos may be sampled by coring, but are also collected by the Brenke sled because this disturbs the sediment while being used. Macrofauna include hard-bodied species and groups (including ostracods, euphausiids, mysids, copepods, tanaids, cumaceans, isopods, bivalves, crabs), and soft-bodied groups (mainly polychaetes, nematodes and chaetognaths). Note that larger species/individuals (especially decapods and swimming polychaetes) may be caught by the Brenke sled but are included in the appropriate megafauna group in the model rather than in the macrofauna group.

Biomass Two sets of data on the macrobenthos of the Chatham Rise were examined, one for the infauna (macrobenthos in the soft sediment itself, dominated by polychaetes) and the second for the hyperbenthic epifauna (macrobenthos living above the surface of the sediments).

In conjunction with the University of Otago, NIWA has made measurements of macrofaunal infaunal biomass on the Chatham Rise on a number of N-S transects close to longitude 180° for some years (Nodder et al. 2003; Probert et al., 1996). Macrofaunal biomass was found to be dominated by polychaetes (50–70%), with significant contributions of amphipods, isopods and ophiuroids. Macrofaunal polychaetes on the Chatham Rise are abundant and diverse, with more than 150 species representing 36 families present. Feeding types include filter feeders, surface deposit feeders, subsurface deposit feeders and predators, with a dominance of surface deposit feeders (Probert et al., 1996, 2009). Probert et al. (1996), using a 1 mm mesh, recorded an overall mean polychaete density of 430 individuals m –2. Probert et al. (2009), using a 0.42 mm mesh, found a mean density of polychaetes of 923 individuals m –2. Assuming a mean mass of detrital polychaete as 3 mgWW ind -1 (about half the weight of detrital polychaetes from shallow water, Pinkerton, 2011) and carbon is assumed to comprise about 7.3% wet weight (Pinkerton 2011; Rowe 1983), we estimate a mean density of macrobenthic polychaetes of 0.20 gC m -2, and a total infaunal biomass of macrofauna of 0.29 gC m -2.

Second, measurements of macrobenthic hyperbenthos biomass were made using the Brenke sled which samples just above (typically 1–2 m) the seabed on the Ocean Survey 20- 20 (Lorz, 2010; Bowden 2011, Figure 15). The sled has an opening of 35 x 100 cm and was fitted with two 500-µm nets with 300 µm cod-ends (Lorz, 2010). Only data from the upper (supra) net of the Brenke sled were used to avoid measuring infaunal macrobenthos. Data are shown in Figure H10 (lower). Here, we assume a mean macrofaunal biomass of 6.1 mgWW ind -1 and carbon is assumed to comprise about 7.3% wet weight of macrofauna (Pinkerton 2011; Rowe 1983). The mean density across all taxonomic units shown in Bowden (2011) is ca. 600 individuals per 1000 m 2. This represents high abundances compared to similar measurements elsewhere and taxon diversity was also high (Lorz, 2010). Selectivity of the NIWA brenke sled for macrobenthos is not known, and here we

Ecosystem Modelling of the Chatham Rise 177

assume selectivity of 0.5. Based on these data we estimate a hyperbenthic macrofaunal biomass of 4.5 mgC m -2 across the Chatham Rise.

To estimate the total macrofaunal biomass we add the infaunal biomass to the hyperbenthic biomass to give an estimate of total macrofaunal biomass of 0.29 gC m -2.

Production A P/B ratio for macrofauna can be estimated from the relationship given by Brey & Gerdes (1998) showing an increase of annual community P/B with water temperature. Annual average bottom water temperature over the Chatham Rise was estimated from depth (e.g. Nodder et al. 2003), and the regression equation of Brey & Gerdes applied for each bathymetric pixel (as above) to give a mean P/B of 0.82 y -1. A P/B ratio of 1.83 y -1 is used by Cartes & Maynou (1998) for polychaetes, whereas Feller & Warwick (1988) suggest that a range of 0.7–4 y -1 is possible. Probert (1986) suggests a P/B ratio of 0.4–1 y -1 is reasonable, with values towards the higher end of this range being more likely.

Consumption In order to estimate food consumption by the macrobenthos, we assume that P/Q is 0.35 following Bradford-Grieve et al. (2003). The macrobenthos is taken as being comprised of (in decreasing order of importance): deposit feeders, infaunal predators, and filter feeders, and to be dominated by polychaetes. We have assumed that the macrobenthos is fuelled largely by consumption of sediment bacteria, meiobenthos, with some macrofanual cannibalism.

Figure H10: Abundance of macrofaunal hyperbenthic crustacean taxa in Brenke sled upper net samples from Chatham Rise (n = 16 sites) and Challenger Plateau (n = 5 sites). Means ±1se. Note log scale on axis.

178 Ecosystem Modelling of the Chatham Rise

References Alldredge, A.L.; Jackson, G.A. (1995). Aggregation in marine systems Deep-Sea Research I 42: 1-8.

Banse, K., Mosher, S., (1980). Adult body size and annual production / biomass relationships of field populations. Ecol. Monogr. 50, 355-379.

Bowden, D.A. (2011). Benthic invertebrate samples and data from the Ocean Survey 20/20 voyages to the Chatham Rise and Challenger Plateau, 2007. New Zealand Aquatic Environment and Biodiversity Report No. 65.

Bradford-Grieve, J.M., Boyd, P.W., Chang, F.H., Chiswell, S., Hadfield, M., Hall, J.A., James, M.R., Nodder, S.D., Shushkina, E.A., (1999). Pelagic ecosystem structure and functioning in the Subtropcial Front region east of New Zealand in Austral winter and spring 1993. J. Plankton Res. 41(1), 405-428.

Bradford-Grieve, J.M., Probert, P.K., Nodder, S.D., Thompson, D., Hall, J., Hanchet, S., Boyd, P., Zeldis, J., Baker, A.N., Best, H.A., Broekhuizen, N., Childerhouse, S., Clark, M., Hadfield, M., Safi, K. and Wilkinson, I. (2003). Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system. Journal of Experimental Marine Biology and Ecology 289: 223-262.

Brey T., Gerdes, D., (1998). High Antarctic macrobenthic community production. J. Exp. Mar. Biol. Ecol. 231, 191-200.

Brey, T. (2005). Population dynamics in benthic invertebrates: a virtual handbook. Alfred Wegener Institute. www.awi- bremerhaven.de/Benthic/Ecosystem/FoodWeb/Handbook

Brown, J.H., Gillooly, J.F., Allen, A.P., Savage, V.M. & West, G.B. (2004). Toward a metabolic theory of ecology. Ecology, 85, 1771–1789.

Buesseler, K.O.; P. W Boyd (2009). Shedding light on processes that control particle export and flux attenuation in the twilight zone. Limnology and Oceanography 54(4): 1210-1232.

Buesseler, K.O., C.H. Lamborg, P.W. Boyd et al. (2007). Revisiting carbon flux through the ocean's twilight zone. Science, 3316, 567-570.

Cartes, J.E.; Maynou, F. (1998). Food consumption by bathyal decapod crustacean assemblages in the western Mediterranean: predatory impact of megafauna and the food consumption-food supply balance in the deep-water food web. Marine Ecology Progress Series 171: 233-246.

Christiansen, B.; Beckmann, W.; Weikert, H. (2001). The structure and carbon demand of the bathyal benthic boundary layer community: a comparison of two oceanic locations in the NE-Atlantic. Deep Sea Research II, 48: 2409-2424.

Ecosystem Modelling of the Chatham Rise 179

Connell, A.; Dunn, M.R.; Forman, J. (2010). Diet and dietary variation of New Zealand hoki Macruronus novaezelandiae. New Zealand Journal of Marine and Freshwater Research 44:289–308.

Dayton, P.K.; Robilliard, G.A.; Paine R.T.; Dayton L.B. (1974). Biological accommodation in the benthic community at McMurdo Sound, Antarctica. Ecological Monographs, 44: 105-128.

Dunn M, Horn P, Connell A, Stevens D, Forman J, Pinkerton M, Griggs L, Notman P, Wood B (2009). Ecosystem-scale trophic relationships: diet composition and guild structure of middle-depth fish on the Chatham Rise. Final Research Report for Ministry of Fisheries Research Project ZBD2004-02, Objectives 1–5. 351 p.

Gage, J.D. (2003). Food inputs, utilization, carbon flow and energetics (Chapter 11). In: Ecosystems of the Deep Oceans, Tyler, P.A. (ed), Ecosystems of the World, Vol 28, Elsevier, pp 313-380.

Galéron, J., M. Sibuet, M.-L. Mahaut, and A. Dinet. (2000). Variation in structure and biomass of the benthic communities at three contrasting sites in the tropical Northeast Atlantic. Marine Ecology Progress Series 197:121-137.

Gambi, M.C.; Bussotti, S. (1999). Composition, abundance and stratification of soft- bottom macrobenthos from selected areas of the Ross Sea shelf (Antarctica). Polar Biology 21: 347-354.

Hewitt, J.; Julian, K.; Bone, E.K. (2011). Chatham–Challenger Ocean Survey 20/20 Post-Voyage Analyses: Objective 10 – Biotic habitats and their sensitivity to physical disturbance. New Zealand Aquatic Environment and Biodiversity Report No. 81.

Hickman, R.W.; J. Illingworth (1980). Condition cycle of the green-lipped mussel Perna canaliculus in New Zealand. Marine Biology 60(1): 27-38.

Jarre-Teichmann, A., Brey, T., Bathmann, U.V., Dahm, C., Dieckmann, G.S., Gorny, M., Klages, M., Pagés, F., Plötz, J., Schnack-Shiel, S.B., Stiller, M., (1997). Trophic flows in the benthic shelf community of the eastern Weddell Sea, Antarctica. In: Battaglia, B., Valencia, J., Walton, D.W.H., (Eds), Antarctic Communities, species, structure and survival. University Press, Cambridge, pp. 118-134.

Lorz, A.-N. (2010). Biodiversity of an unknown New Zealand habitat: bathyal invertebrate assemblages in the benthic boundary layer. Marine Biodiversity DOI: 10.1007/s12526-010-0064-x.

Lundquist, C.J.; M.H. Pinkerton (2008). Collation of data for ecosystem modelling of Te Tapuwae o Rongokako Marine Reserve. Science for conservation 288, Department of Conservation, Wellington, New Zealand.

180 Ecosystem Modelling of the Chatham Rise

Lutz, M. J., K. Caldeira, R. B. Dunbar, and M. J. Behrenfeld (2007). Seasonal rhythms of net primary production and particulate organic carbon flux to depth describe the efficiency of biological pump in the global ocean, J. Geophys. Res., 112, C10011, doi:10.1029/2006JC003706.

Lutz, M.; R. Dunbar; K. Caldeira (2002). Regional variability in the vertical flux of particulate organic carbon in the ocean interior. Global Biogeochemical Cycles, 16(3), DOI: 10.1029/2000GB001383.

Martin, J. H., G. A. Knauer, D. M. Karl, and W. W. Broenkow (1987). VERTEX: Carbon cycling in the northeast Pacific, Deep Sea Res. Part A, 34, 267– 285.

McKnight, D.G. and Probert, P.K. (1997). Epibenthic communities on the Chatham Rise, New Zealand. New Zealand Journal of Marine and Freshwater Research 31:505-513.

Nodder S.D. (1997). Short-term sediment trap fluxes from Chatham Rise, New Zealand. Limnology and Oceanography 42(4): 777–783.

Nodder, S.N. (2011). Voyage Report, TAN1116. Research vessel Tangaroa, 2-20 November 2011. Unpublished document, NIWA, Wellington. Pp 68.

Nodder, S.; Maas, E.; Bowden, D.; Pilditch, C. (2011). Physical, biogeochemical, and microbial characteristics of sediment samples from the Chatham Rise and Challenger Plateau. New Zealand Aquatic Environment and Biodiversity Report No. 70.

Nodder, S.D., Gall, M., (1998). Pigment fluxes in the Subtropical Convergence region, east of New Zealand: relationships to planktonic community structure. N. Z. J. Mar. Freshwat. Res. 32, 441-465.

Nodder, S.D., Northcote, L.C., (2001). Episodic particulate fluxes at southern temperate mid-latitudes (41-42oS), in the Subtropical Front region east of New Zealand. Deep-Sea Res. I 48, 833-864.

Nodder, S.D.; Alexander, B.L. (1998). Sources of variability in geographical and seasonal differences in particulate fluxes from short-term sediment trap deployments, east of New Zealand. Deep-Sea Research I 45: 1739–1764.

Nodder, S.D.; P.W. Boyd; S.M. Chiswell; M.H. Pinkerton; J.M Bradford-Grieve; M.J.N. Greig (2005). Temporal coupling between surface and deep ocean biogeochemical processes in contrasting subtropical and subantarctic water masses, southwest Pacific Ocean. Journal of Geophysical Research, 110(C12): 1-15.

Nodder, S.D.; Pilditch, C.A.; Probert, P.K.; Hall, J.A. (2003). Variability in benthic biomass and activity beneath the Subtropical Front, Chatham Rise, SW Pacific Ocean. Deep-Sea Research I 50(8): 959–985.

Ecosystem Modelling of the Chatham Rise 181

Okey, T.A.; Banks, S.; Born, A.F.; Bustamante, R.H.; Calvopina, M.; Edgar, G.J.; Espinoza, E.; Farina, J.M.; Garske, L.E.; Reck, G.K.; Salazar, S.; Shepherd, S.; Toral-Granda, V.; Wallem, P. (2004). A trophic model of a Galapagos subtidal rocky reef for evaluating fisheries and conservation strategies. Ecological Modelling 172: 383–401.

Piepenburg, D.; Blackburn, T.H.; von Dorrien, C.F.; Gutt, J.; Hall, P.O.J.; Hulth, S.; Kendall, M.A.; Opalinski, K.W.; Rachor, E.; Schmid, M.K. (1995). Partitioning of benthic community respiration in the Arctic (Northwestern Barents Sea). Marine Ecology Progress Series, 118: 199-213.

Pinkerton, M.H. (2011). Ecosystem modelling of the present day and historical periods. Final Research Report for Ministry of Fisheries project ZBD200501, “Long-term Change in New Zealand Coastal Ecosystems”. Pp 113. Includes 10 Appendices (given below).

Pinkerton, M.H.; C.J. Lundquist; E. Jones; A. MacDiarmid (2011). Benthic invertebrates: Trophic modelling of Hauraki Gulf, v106. Appendix 4: Final Research Report for Ministry of Fisheries project ZBD200501, “Long-term Change in New Zealand Coastal Ecosystems”. Pp 82.

Probert, P.K. (1986). Energy transfer through the shelf benthos off the west coast of South Island, New Zealand. New Zealand Journal of Marine and Freshwater Research, 20, 407-417.

Probert, P.K.; Grove, S.L.; McKnight, D.G.; Read, G.B. (1996). Polychaete distribution on the Chatham Rise, Southwest Pacific. Internationale Revue der Gesamten Hydrobiologie 81:577-588.

Probert, P.K.; McKnight, D.G. (1993). Biomass of bathyal macrobenthos in the region of the Subtropical Convergence, Chatham Rise, New Zealand. Deep-Sea Research I, 40: 1003–1007.

Probert, P.K.; C. J. Glasby; S.L. Grove; B.L. Paavo (2009). Bathyal polychaete assemblages in the region of the Subtropical Front, Chatham Rise, New Zealand. New Zealand Journal of Marine and Freshwater Research, 43: 1121–1135.

Ricciardi, A.; Bourget, E. (1998). Weight-to-weight conversion factors for marine benthic macroinvertebrates. Marine Ecology Progress Series, 163: 245-251.

Rowe, G.T. (1983). Biomass and production of the deep-sea macrobenthos. In: Rowe, G.T. (ed) The sea, Vol 8, Deep-sea biology. Wiley, New York, p 97–122.

Suess, E. (1980). Particulate organic carbon flux in the oceans—Surface productivity and oxygen utilization, Nature, 288, 260–263.

Tokeshi, M.; Ota, N.; Kawai, T. (2000). A comparative study of morphometry in shell-bearing molluscs. Journal of Zoology (London), 251, 31-38.

Vinogradov, A.P., (1953). The elementary chemical composition of marine organisms. Memoir of the Sears Foundation for Marine Research, Yale University, New Haven II, 647 pp.

182 Ecosystem Modelling of the Chatham Rise

Wright, D.A.; E.W. Hetsel (1985). Use of RNA:DNA ratios as an indicator of nutritional stress in the Americal oyster Crassostrea virginica. Marine Ecology Progress Series, 25: 199-206.

Ecosystem Modelling of the Chatham Rise 183