SURVEYS OF WADER PREY SPECIES AT LAUDERDALE AND SURROUNDING SITES

LAUDERDALE QUAY PROPOSAL

Prepared by Aquenal Pty Ltd Aquatic Environment Analysts

FOR

Cardno Pty Ltd and Walker Corporation Pty Ltd

September 2008

OPERATIONAL AND DOCUMENT SUMMARY

CLIENT/S: Cardno Pty Ltd and Walker Corporation Pty Ltd

CONSULTANT: Aquenal Pty Ltd ABN 86 081 689 910 G.P.O. Box 828 Hobart Tasmania 7001 Phone 03 62343403 Fax 03 62343539 e-mail: [email protected] website: www.aquenal.com.au

PERSONNEL: Report compiled by: Dr Karen Parsons

Field team leaders: Jeremy Dudding, Daniel Elson, Ty Hibberd

Taxonomy: Dr Patrick Lewis, Mel Hills, Alejandro Velasco-Castrillón, Dr Graham Edgar

Data management: Kathryn Pugh, Hanna Westmore

Project coordinator: Dr Karen Parsons

Report review: Dr Graham Edgar

FIELD WORK: Intertidal benthic infauna: 12th September–11th October 2006, 7th February–6th March 2007 and 6th June–5th July 2007 Epibenthic fauna: 16th-19th July 2007, 12th May 2008.

REPORT: Submitted: 30th September 2008

To be cited as: Aquenal (2008) Surveys of wader prey species at Lauderdale and surrounding sites. Lauderdale Quay Proposal. Report for Cardno Pty Ltd and Walker Corporation Pty Ltd.

Surveys of Wader Prey Species Lauderdale Quay

EXECUTIVE SUMMARY

An invertebrate sampling program was conducted to collect data on wader prey species at Lauderdale and surrounding bays that may have links to the proposed Lauderdale Quay development zone. Sampling was primarily designed to collect data required for a Pied Oystercatcher carrying capacity model, but also to measure densities of prey for other wader species. Survey locations coincided with those of the bird utilisation and foraging studies performed as part of the Lauderdale Quay IIS that similarly provide input to the Pied Oystercatcher carrying capacity model and present data for other waders. The current document is essentially a background data report, and describes trends in the distributions, densities and sizes of prey species amongst bays and amongst three survey zones categorised at Lauderdale. It makes no attempt to estimate the total biomass of available prey resources; this is instead performed by the carrying capacity model using data on invertebrates, foraging behaviour, tidal variation in sandflat exposure, and other environmental and ecological variables.

Prey surveys primarily targeted the bivalves Anapella cycladea and Katelysia scalarina, polychaete worms (the three dominant species Nephtys australiensis, Olganereis edmonsi and Leitoscoloplos normalis, as well as less common taxa), gastropod Salinator fragilis, less common bivalves and epibenthic bivalves Mytilus galloprovincialis and Crassostrea gigas, which together contributed an estimated 98% of the Pied Oystercatcher diet. Density and size data were collected for these ‘main prey’ species, while samples were also obtained for the Ash Free Dry Mass (AFDM) analyses presented in the carrying capacity report. Size measurement data allowed analyses to be limited to animals within the size range consumed by the Pied Oystercatchers, and hence deemed ‘available’ as prey. With the additional analysis of density data for the crabs Paragrapsus gaimardii and Mictyris platycheles, prey species analysed accounted for an average of 75% of the diet of other waders. Prey species were surveyed using benthic infauna cores at sites distributed using a grid design during spring, summer and winter seasons, with the exception of mussels and oysters which were surveyed using epibenthic transects during winter.

For Pied Oystercatchers, the highest mean density of available benthic infauna prey was recorded at South Arm, closely followed by Lauderdale and then Mortimer Bay. Samples from the three Ralphs Bay locations therefore contained the highest densities of Pied Oystercatcher food, while values were intermediate at Barilla Bay, Five Mile Beach and Pipeclay Lagoon, and low at Orielton Lagoon. Patterns of seasonal variation in recruitment, density and mean size of prey species varied amongst bays, and multivariate analysis indicated that temporal within-bay variation in prey assemblage composition was small relative to variation between bays. Orielton Lagoon was a distinct outlier due the absence of available Katelysia scalarina in samples and reduced densities of other main prey species.

Pied Oystercatcher prey species were dominated numerically in all seasons by polychaetes at Mortimer Bay, South Arm, Pipeclay Lagoon and Orielton Lagoon, and by bivalves at Lauderdale and Five Mile Beach, while the dominant prey group varied seasonally at Barilla Bay. The highest densities of bivalve and gastropod prey were recorded at Lauderdale, while counts of polychaetes were highest in samples from South Arm and Mortimer Bay. The density of bivalves at Lauderdale was attributable to this location recording the highest counts of both Katelysia scalarina and Anapella cycladea of any bay, while Mortimer Bay and South Arm recorded the next highest densities of K. scalarina but low to negligible numbers of A. cycladea. The latter two bays were the only locations to record K. scalarina at higher densities than A. cycladea, a finding which may reflect their steeper upper shores and hence reduced habitat for the latter predominantly high-shore species. High densities of polychaetes at South Arm and Mortimer Bay were attributable to elevated counts of Nephtys australiensis and Olganeresi edmonsi, while Mortimer Bay also recorded the highest counts of Leitoscoloplos normalis. These results indicate that the highest densities of all main prey benthic infauna species were recorded in one or more of the Ralphs Bay sites, although the bivalve A. cycladea was most common at Lauderdale and reached similarly high densities at Barilla Bay.

i Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Surveys of oyster/mussel beds were conducted at Lauderdale (north, development zone), South Arm and Pipeclay Lagoon (north), the primary areas where these species were identified as Pied Oystercatcher prey. Mussels within the dietary size range reached higher densities than the oysters, the latter being dominated by individuals too large for the birds to handle. The largest mussel/oyster beds were found at Lauderdale and South Arm, with combined data on areal extent and density suggesting that populations may be largest at South Arm although potentially less accessible due to a steeper shore profile and tidal effects.

The proportional contributions of prey types to the total prey assemblage in benthic infauna samples (current study) were compared with data on proportional contributions of these prey types to the diet (foraging study) to assess whether Pied Oystercatchers exhibit prey selectivity or forage in accordance with availability. Results indicate selectivity for the bivalve Katelysia scalarina, particularly at Lauderdale and Mortimer Bay but also to a lesser extent in most other bays, presumably due to its larger adult size and therefore higher energetic profitability. Orielton Lagoon was the only location where the smaller bivalve Anapella cycladea was preferentially consumed, possibly due to the absence of available K. scalarina. Five Mile Beach was the only bay where the overall mean availability of benthic infauna prey items closely reflected the proportions of consumed items.

Benthic infauna prey were sampled in three spatial survey zones at Lauderdale: N1 (majority of the development zone), N2 (south of N1, but north of the southern narrow channel) and S (southern sandflat). Based on pooled seasonal data, total mean densities of available prey increased from north to south primarily due to large increases in the density of the bivalve Anapella cycladea towards the southern end of the sandflat. The gastropod Salinator fragilis also increased in density towards the south, while the larger bivalve Katelysia scalarina – a less common species at Lauderdale than A. cycladea – reached highest densities in the northern zones and the northern section of zone S, with lowest numbers at the very southern end of the sandflat. Densities of polychaetes were also elevated at the northern end due to higher counts of Nephtys australiensis and higher seasonal recruitment of Olganereis edmonsi. Multivariate analysis of prey assemblage data indicated considerable overlap between N1 and N2, whilst S formed a distinct subgrouping due to higher densities of A. cycladea and S. fragilis, and lower densities of N. australiensis and K. scalarina overall. Epibenthic mussels and oysters are only available as a foraging resource in N1 and contribute further to north-south differentiation in prey.

Seasonal variation in prey community composition was reduced at zone S compared with the northern Lauderdale zones, with N1 and N2 demonstrating similar changes with season. This was demonstrated by comparable seasonal recruitment patterns for the common species Anapella cycladea and Nephtys australiensis in N1 and N2, but contrasting growth and/or recruitment in the south. Subtle differences in levels of coarse material and sizes of sand fractions may help to explain the differentiation of S, which is more protected from wind and wave effects. In addition, zones N1 and N2 incorporate a wide range of tidal elevations, whilst a large portion of the southern sandflat has a high elevation and hence reduced level of tidal inundation. On the basis of shore heights, zones N1 and N2 and the northern part of zone S provide a reliable year-round supply of food for Pied Oystercatchers. The foraging studies found that the southern part of zone S opposite East Marsh Lagoon was rarely used for foraging during summer, which may be associated with higher shore elevation and hence susceptibility to drying. It is notable that targeted sampling of the seagrass habitat specific to zone S found that bivalves (A. cycladea primarily) continued to dominate the prey assemblage, while targeted sampling of the rocky habitats specific to N1 recorded a change in dominances for this zone, with the bivalve A. cycladea more abundant than polychaetes. The wide range of sedimentary substrata in N1 therefore suggests that this zone provides the highest diversity of prey assemblages.

Comparisons between invertebrate and foraging data suggested preferential foraging by Pied Oystercatchers on the bivalve Katelysia scalarina in all Lauderdale survey zones, while mussels and oysters provide additional high value prey that are only available in N1. Preferential feeding on polychaetes over the highly abundant, small Anapella cycladea individuals at the southern end of the sandflat suggests that, where the larger items such as adult K.

ii Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay scalarina and oysters/mussels are less available, polychaetes may be more profitable than small bivalves due to shorter handling times.

The foraging study found that the Eastern Curlew (a large wader species) fed almost exclusively on the crab Paragrapsus gaimardii, whilst polychaetes numerically dominated the diets of intermediate sized waders and also contributed a considerable portion of prey for smaller waders. Invertebrate samples recorded P. gaimardii at Lauderdale and Pipeclay Lagoon in all three seasons, and in one or two seasons from all other bays except Orielton Lagoon. The combined low density, high mobility and diurnal variation in habitat utilisation of this species are likely to result in considerable stochastic noise in the abundance dataset. This may explain the lack of correlation between invertebrate availability data and foraging observations, the latter recording Eastern Curlews feeding in all seasons in Orielton Lagoon, the only bay where P. gaimardii was absent from all invertebrate samples. This discrepancy highlights the difficulty in sampling low density, mobile invertebrate species, and also indicates the very selective nature of the Eastern Curlew diet. Consistent with observations of Eastern Curlews foraging at Lauderdale during bird utilisation surveys, invertebrate data recorded P. gaimardii in all Lauderdale survey zones. Densities were relatively uniform across the zones, although the more sheltered sand and seagrass habitats at the southern end are more likely to support small individuals of reduced energetic value.

Variation in the availability of polychaetes for intermediate and smaller waders has been summarised above in relation to the Pied Oystercatcher. There was no clear relationship between polychaete density and the distribution of foraging waders, since some bays that recorded comparatively low densities of polychaetes (e.g. Orielton Lagoon) were found to be particularly important foraging sites. Similarly, the small and intermediate waders appear to infrequently utilise Mortimer Bay for foraging even though invertebrate samples collected there contained a high density of polychaetes. This indicates that utilisation of foraging habitat in these species across the wider study area cannot be predicted from densities of main prey types alone. At Lauderdale, invertebrate samples recorded seasonally reduced densities of polychaetes at the southern end of the sandflat, which is consistent with waders primarily feeding in the northern zones. Their preference for N1 over N2 cannot be explained on the basis of mean density and size data for polychaetes. While the carrying capacity model being developed as part of the Lauderdale Quay IIS applies specifically to the Pied Oystercatcher, it will include total available biomass estimates for particular resource types, and hence estimates for polychaetes will provide further detail on spatial and temporal variation in resources available to other waders.

iii Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

CONTENTS

1 Introduction ...... 1

2 Scope of Document ...... 2

3 Methods ...... 3

3.1 Survey Sites and Timing...... 3 3.2 Wader Prey Species and Sizes ...... 5 3.2.1 Pied Oystercatcher...... 5 3.2.2 Other wader species ...... 7

3.3 Design of Sampling Regime...... 8 3.3.1 Benthic infauna sampling in each bay...... 8 3.3.2 Additional benthic infauna sampling at Lauderdale...... 21 3.3.3 Epibenthic sampling at Lauderdale, Pipeclay Lagoon and South Arm ...... 23 3.3.4 Identification of ‘patches’ for the Pied Oystercatcher carrying capacity model...... 23

3.4 Field Survey Methodology ...... 28 3.4.1 Benthic infauna field sampling...... 28 3.4.2 Epibenthic fauna field sampling...... 30

3.5 Laboratory and Analytical Methods ...... 30 3.5.1 Benthic infauna samples...... 30 3.5.2 Epibenthic fauna samples...... 32 3.5.3 Data analyses...... 32 3.5.3.1 Data input for the Pied Oystercatcher carrying capacity model ...... 32 3.5.3.2 Descriptive statistics...... 34

4 Results...... 35

4.1 Input Data for the Pied Oystercatcher Carrying Capacity Model...... 35 4.2 Intertidal Benthic Infauna...... 35 4.2.1 Comparisons between bays ...... 35 4.2.2 Variation at Lauderdale...... 62

4.3 Epibenthic Fauna...... 87

5 Summary and Discussion...... 95

6 References ...... 104

iv Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

LIST OF FIGURES

Figure 1 Site plan for the proposed Lauderdale Quay development...... 1 Figure 2 Bays surveyed for wader prey species (enclosed in black squares). Orange shaded areas represent intertidal sandflat habitats...... 4 Figure 3 Intertidal benthic infauna sampling sites and habitats at Lauderdale (northern half)...... 13 Figure 4 Intertidal benthic infauna sampling sites and habitats at Lauderdale (southern half)...... 14 Figure 5 Intertidal benthic infauna sampling sites at Barilla Bay...... 15 Figure 6 Intertidal benthic infauna sampling sites at Five Mile Beach...... 16 Figure 7 Intertidal benthic infauna sampling sites at Mortimer Bay...... 17 Figure 8 Intertidal benthic infauna sampling sites at Orielton Lagoon...... 18 Figure 9 Intertidal benthic infauna sampling sites at Pipeclay Lagoon...... 19 Figure 10 Intertidal benthic infauna sampling sites at South Arm...... 20 Figure 11 Map indicating the boundaries of survey zones N1, N2 and S (bold black lines) at Lauderdale, and the outline of the development disturbance area (red line). Grids and locations of survey sites are also indicated...... 22 Figure 12 Location of the mussel and oyster foraging area at Lauderdale (top; indicated by the black box) and position of epibenthic survey transects positioned within it (bottom)...... 24 Figure 13 Location of the mussel and oyster foraging area at Pipeclay Lagoon (top; indicated by the black box) and position of epibenthic survey transects positioned within it (bottom)...... 25 Figure 14 Location of the mussel and oyster foraging area at South Arm (top; indicated by the black box) and position of epibenthic survey transects positioned within it (bottom)...... 26 Figure 15 Distributions of survey zone ‘patches’ in each bay: a) Five Mile Beach; b) Mortimer Bay; c) Barilla Bay; d) South Arm; e) Orielton Lagoon; f) Lauderdale; and g) Pipeclay Lagoon. A 500 m scalebar has been included in the map for each bay...... 27 Figure 16 MDS plot of mean densities of prey species for bays in each season surveyed (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007. Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm)...... 40 Figure 17 MDS plots of mean densities of prey species for sites in each bay and in each season surveyed in accordance with tide height category (Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm; Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore)...... 41 Figure 18 MDS plot of mean densities of prey species individuals ≥ 10 mm for bays in each season surveyed (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007. Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm)...... 47 Figure 19 MDS plots of mean densities of prey species for sites in each bay and in each season surveyed in accordance with tide height category and only including ≥ 10 mm individuals (Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm; Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore)...... 48 Figure 20 Size frequency histograms for the bivalve Anapella cycladea in each bay, with data provided for the three seasons surveyed. Note that no A. cycladea ≥ 10 mm were recorded from Mortimer Bay grid samples. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable...... 50 Figure 21 Size frequency histograms for the bivalve Katelysia scalarina in each bay, with data provided for the three seasons surveyed. Note that no K. scalarina ≥ 10 mm were recorded from Orielton Lagoon samples. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable...... 51

v Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Figure 22 Size frequency histograms for the other bivalve species (pooled) in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable...... 52 Figure 23 Size frequency histograms for the polychaete Nephtys australiensis in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable...... 53 Figure 24 Size frequency histograms for the polychaete Leitoscoloplos normalis in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable...... 54 Figure 25 Size frequency histograms for the polychaete Olganereis edmonsi in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable...... 55 Figure 26 Size frequency histograms for other polychaetes (pooled) in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable...... 56 Figure 27 Box plots for particle size categories (>2 mm = coarse material - e.g. gravel, 2 mm–>0.5 mm = coarse sand, 0.5 mm->0.063 mm = fine to medium sand, ≤0.063 mm = silt/clay) at sites in each bay (refer to Bay name abbreviations in the Figure 28 caption)...... 59 Figure 28 Box plots for redox potential values at 1 cm, 4 cm and ~10 cm (or greatest depth possible to a maximum of 10 cm) depths in sediment core samples (Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm)...... 61 Figure 29 MDS plot of mean densities of prey species for Lauderdale survey zones in each season surveyed, based on grid survey sites (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007)...... 65 Figure 30 MDS plots of mean densities of prey species for habitats sampled in each Lauderdale survey zone (Habitats: S = unvegetated sand, G = seagrass, R = sand interspersed with rocks, P = sand interspersed with pebbles, D = dense rocky rubble)...... 66 Figure 31 Tide height categories allocated at Lauderdale to assess variation in prey species composition with level of tidal inundation...... 68 Figure 32 MDS plots of mean densities of prey species of all sizes at different tide heights in each Lauderdale survey zone (Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore)...... 69 Figure 33 MDS plot of mean densities of prey species for Lauderdale survey zones in each season surveyed on the basis of individuals ≥ 10 mm collected at grid sites (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007)...... 73 Figure 34 MDS plot of mean densities of prey species for Lauderdale survey zones in each season surveyed on the basis of individuals ≥ 10 mm collected at grid sites and additional non-grid sites (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007)...... 73 Figure 35 MDS plots of mean densities of ≥ 10 mm prey species for habitats sampled in each Lauderdale survey zone (Habitats: S = unvegetated sand, G = seagrass, R = sand interspersed with rocks, P = sand interspersed with pebbles, D = dense rocky rubble)...... 75 Figure 36 MDS plots of mean densities of ≥ 10 mm prey species at different tide heights in each Lauderdale survey zone (Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore)...... 76 Figure 37 Size frequency histograms for the bivalve Anapella cycladea in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w)...... 79 Figure 38 Size frequency histograms for the bivalve Katelysia scalarina in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w)...... 80 vi Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Figure 39 Size frequency histograms for the other bivalve species (pooled) in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w)...... 81 Figure 40 Size frequency histograms for the polychaete Nephtys australiensis in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w)...... 82 Figure 41 Size frequency histograms for the polychaete Leitoscoloplos normalis in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w)...... 83 Figure 42 Size frequency histograms for the polychaete Olganereis edmonsi in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w)...... 84 Figure 43 Size frequency histograms for the other polychaete species (pooled) in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w)...... 85 Figure 44 Particle size distributions in intertidal core samples from sites in survey zones N1, N2 and S at Lauderdale...... 88 Figure 45 Redox potential values at sediment depths of 1 cm, 4 cm and ~10 cm (or greatest depth possible to a maximum of 10 cm) in intertidal core samples from sites in survey zones N1, N2 and S at Lauderdale...... 89 Figure 46 Size frequency histograms for the Pacific oyster Crassostrea gigas in each bay surveyed indicating the size classes within the prey size range of Pied Oystercatchers (‘Wader prey’). n = number of 5 m transect intervals surveyed...... 93 Figure 47 Size frequency histograms for the native blue mussel Mytilus galloprovincialis in each bay surveyed indicating the size classes within the prey size range of Pied Oystercatchers (‘Wader prey’). n = number of 5 m transect intervals surveyed...... 94

vii Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

LIST OF TABLES

Table 1 Summary of Pied Oystercatcher prey species and sizes at Lauderdale and surrounding bays as identified by Harrison (2008). Shaded prey items were not incorporated in the Pied Oystercatcher carrying capacity model..... 6 Table 2 Summary of prey species and sizes at Lauderdale and surrounding bays for other wader species, as identified by Harrison (2008)...... 8 Table 3 Numbers of sites and samples in each bay for grid sampling designs and additional areas surveyed to target specific habitats (and survey zones, Lauderdale)...... 11 Table 4 Site symbols in benthic infauna sampling maps for Lauderdale and other bays...... 12 Table 5 Less common bivalve and polychaete species pooled with main prey species for model input...... 34 Table 6 Mean abundance per core sample of wader prey species in each bay including all individuals collected in core samples (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon)...... 37 Table 7 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each bay, including all individuals collected (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon)...... 38 Table 8 Pooled mean abundances per core sample across seasons for wader prey species in each bay, including all individuals collected (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon)...... 38 Table 9 Mean abundance per core sample of wader prey species individuals ≥ 10 mm length (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon)...... 44 Table 10 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each bay, on the basis of individuals ≥ 10 mm (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon)...... 45 Table 11 Pooled mean abundances per core sample across seasons for wader prey species in each bay on the basis of individuals ≥ 10 mm (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon)...... 45 Table 12 Mean sizes (mm) of prey species in each bay based on measured individuals ≥ 10 mm in grid samples. Red highlighted values indicate surrogate data based on non-grid sites where grid samples contained no individuals ≥ 10 mm...... 57 Table 13 Mean abundance per core sample of wader prey species in each Lauderdale survey zone (N1, N2 and S) including all individuals collected in core samples...... 63 Table 14 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each Lauderdale survey zone (N1, N2 and S) including all individuals collected...... 64 Table 15 Pooled mean abundances per core sample across seasons for wader prey species in each Lauderdale survey zone (N1, N2 and S) including all individuals collected...... 64 Table 16 Mean abundance per core sample of prey species ≥ 10 mm length at the Lauderdale survey zones...... 70 Table 17 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each Lauderdale survey zone (N1, N2 and S) on the basis of individuals ≥ 10 mm...... 71 Table 18 Pooled mean abundances per core sample across seasons for wader prey species in each Lauderdale survey zone (N1, N2 and S) on the basis of individuals ≥ 10 mm...... 71 Table 19 Mean sizes (mm) of prey species for tidal height categories at Lauderdale based on individuals ≥ 10 mm in combined grid and non-grid samples (category 1 = highest on shore, category 4 = lowest; refer to Figure 31)..... 77

viii Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 20 Mean sizes (mm) of prey species in Lauderdale survey zones based on individuals ≥ 10 mm in combined grid and non-grid samples...... 86 Table 21 Mean densities of oysters and mussels based on animals of all sizes...... 91 Table 22 Mean densities of oysters and mussels based on animals within the size range consumed by Pied Oystercatchers...... 91 Table 23 Mean sizes of oysters and mussels based on all animals observed and animals within the dietary size range of the Pied Oystercatcher...... 95

ix Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

LIST OF APPENDICES

Appendix 1 Geographical coordinates (WGS84) of intertidal benthic infauna sampling sites...... 105

x Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

1 INTRODUCTION

Walker Corporation has proposed to construct a marina village development in Ralphs Bay, a sheltered embayment of the lower Derwent Estuary in south eastern Tasmania. The proposed development, known as Lauderdale Quay, is located in the northern section of an embayment of greater Ralphs Bay adjacent to Lauderdale. It is largely located in the intertidal zone where it occupies 86 ha (0.86 km2) of intertidal sandflat. A site plan for the proposed Lauderdale Quay development is included below in Figure 1.

Figure 1 Site plan for the proposed Lauderdale Quay development.

The intertidal sandflat at the northern end of the Lauderdale embayment will be reclaimed and dredged to form channels during construction of the development, resulting in loss of intertidal foraging habitat and resources for wading birds that use the site. The waders that occur in this area are described in the bird utilisation technical reports prepared as input to the Integrated Impact Statement (IIS) for the development project (see Aquenal 2008a, Aquenal and Biosis 2008). The wader species that occurs in greatest numbers at Lauderdale is the resident Pied Oystercatcher Haemotopus longirostris, a species that is categorised as being of high conservation significance in Tasmania, although not listed as threatened. The Lauderdale population of this species comprises ~ 2.4-2.6% of the world population, a statistic that is significant because it satisfies one of the Ramsar criteria (Aquenal 2008a). A carrying capacity model has been developed in England for an ecologically similar species of oystercatcher and has been adapted to H. longirostris in southern Tasmania to enable modelling of carrying capacity for this species at Lauderdale and surrounding bays as part of the Lauderdale Quay IIS studies (Atkinson and Stillman 2008). The current survey was designed primarily to collect invertebrate prey data suitable as input to this model, complementing Pied Oystercatcher foraging ecology data collected as model input by Harrison (2008).

1 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Other important wader species have also been identified at Lauderdale that are listed as migratory under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBCA) and, in one case, also as threatened under the Tasmanian Threatened Species Protection Act 1995 (TSPA). While suitable carrying capacity models were not identified and therefore not applied to these additional species for the Lauderdale Quay IIS, data were collected in the current study to describe the distributions and densities of prey species for other waders. Similarly, Harrison (2008) compiled descriptive data on the foraging ecology of other wader species present at Lauderdale and surrounding bays. Therefore, while the Pied Oystercatcher was the primary focus of prey and foraging surveys, the current report also provides information on prey density for other waders, complementing foraging data compiled for these species by Harrison (2008).

Occasional studies of invertebrate communities have been undertaken at Lauderdale and surrounding bays, however these have generally focussed on saltmarsh rather than sandflat species (e.g. Marsh 1982), have investigated particular taxa that include only a portion of potential wader prey species (e.g. Woodward 1985), or are unpublished and not available for consideration in the IIS. The absence of invertebrate data suitable as input for the wader foraging resource and carrying capacity assessments of the IIS necessitated a sampling program aimed at collecting information on prey species for Pied Oystercatchers and other important waders. Species of relevance as prey were determined initially at Lauderdale through a preliminary site investigation undertaken with the assistance of Dr Philip Atkinson of the British Trust of Ornithology (BTO), and subsequently at Lauderdale and surrounding bays through more detailed wader foraging studies (Harrison 2008). For the Pied Oystercatcher, information collected during the invertebrate sampling program was used here to describe the densities of prey species in each bay/area surveyed and to provide data input for the carrying capacity model being applied to this species (Atkinson and Stillman 2008). For additional wader species, invertebrate data collected were used to describe the distributions and densities of key prey types.

Note that while the sampling program described was conducted primarily to provide input for wader carrying capacity and ecology assessments, samples collected were also analysed for non-wader prey species to describe patterns of invertebrate species diversity and health at a community level. The latter results are included in the estuarine and marine ecology report prepared for the IIS (Aquenal 2008b), such that there is some overlap between the marine ecology and current reports in descriptions of survey design and sampling methodologies.

2 SCOPE OF DOCUMENT

The current document provides a background data report to the Pied Oystercatcher carrying capacity model and makes no attempt to estimate the total biomass of foraging resources available to waders in each area surveyed. Data are presented using descriptive statistics and summaries of trends rather than detailed tests of statistical significance, since the meaningful analysis of the data is undertaken in the carrying capacity modelling study. This modelling study utilises data on invertebrates, tidal variation in sandflat exposure, wader ecology and other environmental variables to address the complex issue of quantifying the total foraging resource available to Pied Oystercatchers (Atkinson and Stillman 2008). Background data on prey densities for other waders are also provided here, and while carrying capacity models were not applied to these species, the Pied Oystercatcher modelling study includes estimation of total available resources of polychaetes, a prey type shared between Pied Oystercatchers and other intermediate and smaller wader species. The study of Atkinson and Stillman (2008) therefore provides more detailed analyses of seasonal and spatial variation in the availability of this prey resource, with the results relevant to other waders as well as Pied Oystercatchers.

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3 METHODS

3.1 SURVEY SITES AND TIMING

The study examined invertebrate sandflat populations at Lauderdale and a range of additional bays that were considered to have potential links to the proposed Lauderdale Quay development site. These bays also coincided with areas that had been surveyed annually in summer and winter by Birds Tasmania. The full rationale for bays selected for surveying is included in the diurnal bird utilisation technical report prepared as input to the IIS (Aquenal 2008a).

Surveying was performed on sandflats at a total of seven bays, as listed below and illustrated in Figure 2. The study area at Lauderdale included the entire tidal sandflat, consisting of the proposed development site at the northern end and the sandflat habitat to the south of the development site. East Marsh Lagoon was not included since tidal flows in this area are prevented by the causeway and other sampling indicated the absence of wader prey species in the lagoon (Aquenal 2008b).

• Lauderdale • Mortimer Bay • South Arm • Pipeclay Lagoon • Five Mile Beach • Barilla Bay • Orielton Lagoon

Note that Carlton and Sorell Rivulet/Iron Creek were also included in the study initially, but were omitted following initial wader survey work, as outlined in Aquenal (2008a).

The main prey species initially identified for waders were polychaetes and bivalves that are a component of the benthic infauna community. An intertidal benthic infauna sampling program was therefore devised, with surveys to occur during three seasons in accordance with the lifecycles of important wader species:

• Spring (2006): prior to the arrival of the majority of migratory waders • Late summer (2007): towards the end of the migratory wader season • Winter (2007): during a period when waders consist primarily of residents and one migrant from New Zealand (Double-banded Plover Charadrius bicinctus).

During the course of the winter 2007 wader foraging studies performed by Harrison (2008), it became apparent that Pied Oystercatchers also feed on epibenthic oysters and mussels primarily in small areas of three bays: Lauderdale, Pipeclay Lagoon and South Arm. These species had not been targeted by benthic infauna surveys and hence were investigated using a separate methodology. While it was not possible to obtain data for epibenthic oysters and mussels to the same seasonal design, surveys were conducted for these species in July 2007 (Lauderdale, Pipeclay Lagoon) and May 2008 (South Arm). The South Arm survey was conducted at a later time because of unfavourable tides during July 2007.

3 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Figure 2 Bays surveyed for wader prey species (enclosed in black squares). Orange shaded areas represent intertidal sandflat habitats.

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3.2 WADER PREY SPECIES AND SIZES

Information is summarised below on prey items for the Pied Oystercatcher and migratory waders. More detailed results from the wader foraging ecology surveys are described by Harrison (2008), but summaries are included here to provide context for the invertebrate survey methodologies and target species.

3.2.1 Pied Oystercatcher

Based on an initial site visit to Lauderdale by Dr Philip Atkinson of the British Trust of Ornithology (BTO) in July 2004, it was determined that the most common wader species observed, the Pied Oystercatcher, was feeding primarily on bivalves and polychaete worms. Aquenal performed some preliminary sampling of benthic infauna communities, and a combination of the invertebrate data collected and observations of Dr Atkinson suggested that the following were the key prey species:

Bivalves: • Anapella cycladea • Katelysia scalarina • Other less commonly consumed bivalves

Polychaetes; size classes and numbers in invertebrate samples suggested the most likely prey species to be: • Nephtys australiensis • Leitoscoloplos normalis • Olganereis edmonsi • Other less common polychaetes within the size range consumed by the birds

These species therefore became the primary target species of subsequent investigations of wader prey starting in September 2006, with information on prey refined through the subsequent more detailed foraging surveys performed by Harrison (2008) between April 2007 and February 2008. Table 1 provides a summary of information on species and sizes of prey consumed by Pied Oystercatchers at Lauderdale and surrounding bays, as compiled by Harrison (2008). For each prey type, its percentage contribution to the total number of prey items consumed across all seasons is provided.

The foraging surveys of Harrison (2008) confirmed that Anapella cycladea and Katelysia scalarina are the main bivalve species consumed, whilst a range additional bivalve species were less commonly consumed. During these foraging ecology surveys it was not feasible to identify polychaetes to species level, since these require close inspection for identification and, unlike bivalves, leave no remains once consumed. Collection of Pied Oystercatcher droppings was performed to examine for evidence of polychaete species. The presence of Olganereis edmonsi was confirmed from the droppings, but it was not feasible to differentiate parts of most other polychaete species. Advice suggests that the Pied Oystercatchers are unlikely to feed in a species-specific way on polychaetes, but instead consume all worms within a certain size range (P. Atkinson BTO, pers. comm.). On this basis, the above three listed species were determined to be the likely main polychaete prey species, while any additional polychaetes within the dietary size range were also included in the invertebrate analyses.

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Table 1 Summary of Pied Oystercatcher prey species and sizes at Lauderdale and surrounding bays as identified by Harrison (2008). Shaded prey items were not incorporated in the Pied Oystercatcher carrying capacity model.

Prey Type Taxonomic Group % count of total Minimum Maximum prey items size (mm) size (mm) Nephtys australiensis Polychaete (Annelida) 46.68 5.0 200.0 Leitoscoloplos normalis Polychaete (Annelida) Olganereis edmonsi Polychaete (Annelida) Other polychaete species Polychaete (Annelida) Katelysia scalarina Bivalvia (Mollusca) 20.32 7.7 48.2 Anapella cycladea Bivalvia (Mollusca) 22.78 8.8 32.6 Tellina deltoidalis Bivalvia (Mollusca) 2.85 10.3 49.9 Eumarcia fumigata Bivalvia (Mollusca) 0.22 19.1 33.3 Laternula tasmanica Bivalvia (Mollusca) 0.47 25.0 48.0 Wallucina assimilis Bivalvia (Mollusca) 0.03 15.8 22.0 Soletellina biradiata Bivalvia (Mollusca) 1.13 19.0 54.7 Mytilus galloprovincialis Bivalvia (Mollusca) 0.94 22.7 82.1 Crassostrea gigas Bivalvia (Mollusca) 0.23 30.0 69.0 Salinator fragilis Gastropoda (Mollusca) 2.18 10.0 20.0 Xenostrobus inconstans Bivalvia (Mollusca) 0.09 10.8 43.7 Electroma georgiana Bivalvia (Mollusca) 0.09 12.3 29.4 Barnacle Cirripedia (Crustacea) 0.03 10.0 10.0 Paragrapsus gaimardii Decapoda (Crustacea) 0.24 20.0 40.0 Mictyris platycheles Decapoda (Crustacea) 0.92 10.0 30.0 Unidentified crab Decapoda (Crustacea) 0.10 20.0 30.0 Amphipod Amphipoda (Crustacea) 0.05 5.0 10.0 Ascidian Ascidiacea (Chordata) 0.40 20.0 50.0 Beetle Coleoptera (Insecta) 0.24 10.0 20.0

In addition to the above bivalve and polychaete species, the detailed foraging ecology studies found that the gastropod Salinator fragilis was a regularly consumed item in some areas. Observations during the initial winter 2007 foraging ecology surveys indicated that S. fragilis was likely to be an important food item at Lauderdale, South Arm and south Pipeclay Lagoon. For these areas, S. fragilis was therefore analysed in addition to bivalves and polychaetes. The native blue mussel Mytilus galloprovincialis and Pacific oyster Crassostrea gigas were consumed by Pied Oystercatchers primarily in small areas at north Lauderdale, north Pipeclay Lagoon and western South Arm. These two species did not comprise a large numerical proportion of the diet, however they are larger than other prey and hence were considered important due to their higher energetic values. Epibenthic populations of mussels and oysters were therefore surveyed in the above three areas to provide prey resource data, as described in Section 3.3.3.

On the basis of the above, the foraging study of Harrison (2008) classified the benthic infauna polychaetes (identified here as being dominated by Nephtys australiensis, Leitoscoloplos normalis and Olganereis edmonsi) and

6 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay bivalves Anapella cycladea and Katelysia scalarina as ‘main prey’ species for the Pied Oystercatcher. These species together accounted for ~ 90% of the Pied Oystercatcher diet. For the purpose of the current report, the gastropod Salinator fragilis and epibenthic bivalves Mytilus galloprovincialis and Crassostrea gigas, which were important components of the diet in some areas, were also categorised as main prey and were targeted during field surveying and sample analysis.

Note that in addition to the above main prey species, a range of other bivalve species were observed to be consumed by Pied Oystercatchers and were therefore also analysed in the invertebrate samples (refer to non-shaded examples in Table 1). Similarly, additional polychaete species were identified in the invertebrate samples and, where they fell within the dietary size range of the Pied Oystercatcher, were included in the prey dataset (see Section 3.5.3.1). All species observed as prey during the foraging ecology surveys and subsequently included in the Pied Oystercatcher carrying capacity model are indicated in Table 1 (i.e. non-shaded items). On the basis of counts, these prey species contributed 98% of the total prey items consumed by Pied Oystercatchers during the foraging ecology surveys. The additional non-main prey species identified in the invertebrate samples and subsequently incorporated in the model input are listed in Section 3.5.3.1.

Other prey items identified in the field by Harrison (2008) contributed smaller proportions of total prey item counts. These items, which include the shaded species in Table 1, were excluded from the carrying capacity model on account of low rates of consumption and small masses (e.g. amphipods, barnacles, beetles), or low rates of consumption combined with lack of applicable size and Ash Free Dry Mass data (and density data for certain epibenthic species). The latter absence of survey data applied to species that were not identified as prey by the foraging ecology surveys until components of the invertebrate survey program were completed. These prey species were only identified from a small number of survey areas and were not observed as prey in all seasons.

3.2.2 Other wader species

Harrison (2008) also recorded foraging observations for additional wader species found within the survey area, the majority of which are listed as marine or migratory species on the schedules of the Environment Protection and Biodiversity Conservation Act 1999 (EPBCA), while one species – the Eastern Curlew Numenius madagascariensis – is also listed as threatened under the Tasmanian Threatened Species Protection Act 1995 (TSPA) (Aquenal 2008a). Species studied by Harrison (2008) included: the Bar-tailed Godwit, Eastern Curlew, Grey Tattler, Red-cap Plover, Red-necked Stint, Sooty Oystercatcher, Curlew Sandpiper, Double-banded Plover, Greenshank and Whimbrel [refer to Harrison (2008) for scientific names]. A summary of prey data is provided in Table 2, and includes contributions of prey types to the total count of dietary items on the basis of pooled data for all (non-Pied Oystercatcher) wader species in all three seasons surveyed. Note that as described in Section 3.2.1 for the Pied Oystercatcher, it was not feasible during foraging observations to delineate polychaete species, however they have again been assumed to consist primarily of the three most common species in the invertebrate samples that are within the size range consumed by the birds.

Some of the prey types include species not targeted by the invertebrate sampling program, such as ascidians, flies and fish. Section 0 indicates which of the prey species observed by Harrison (2008) could be analysed in the datasets collected during the current invertebrate sampling program. It is notable that there was overlap in the prey species consumed by Pied Oystercatchers (Section 3.2.1) and other waders, although summary data indicate some differences in percentage contributions of prey types to total prey consumed during observations. For example, the summary data suggest that the bivalves Anapella cycladea and Katelysia scalarina were more frequently preyed upon by Pied Oystercatchers than other waders, while the reverse was true for the crab Paragrapsus gaimardii and amphipods (Table 2). The species that together contributed 98% of prey items for the Pied Oystercatcher (Section 3.2.1 above) contributed 65% of items for other waders, although it is notable that of the remaining 35%, 15.5% consisted of unidentified prey (Table 2).

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Table 2 Summary of prey species and sizes at Lauderdale and surrounding bays for other wader species, as identified by Harrison (2008).

Prey Type Taxonomic Group % count of Minimum Maximum total prey items size (mm) size (mm) Nephtys australiensis Polychaete (Annelida) 56.76 10 120 Leitoscoloplos normalis Polychaete (Annelida) Olganereis edmonsi Polychaete (Annelida) Other polychaete species Polychaete (Annelida) Katelysia scalarina Bivalvia (Mollusca) 0.7 20 20 Anapella cycladea Bivalvia (Mollusca) 1.82 10 24 Tellina deltoidalis Bivalvia (Mollusca) 0.1 30 30 Soletellina biradiata Bivalvia (Mollusca) 2.12 19.8 45.4 Mytilus galloprovincialis Bivalvia (Mollusca) 0.51 30 30 Fulvia tenuicostata Bivalvia (Mollusca) 0.61 13.8 22.6 Salinator fragilis Gastropoda (Mollusca) 2.63 8 15 Paragrapsus gaimardii Decapoda (Crustacea) 8.59 10 60 Mictyris platycheles Decapoda (Crustacea) 1.82 5 20 Shrimp Decapoda (Crustacea) 0.4 30 40 Amphipod Amphipoda (Crustacea) 6.26 5 10 Ascidian Ascidiacea (Chordata) 0.91 20 20 Fly Diptera (Insecta) 1.01 5 5 Fish Osteichthyes (Vertebrata) 0.3 100 150 Unidentified Unknown 15.45 5 30

3.3 DESIGN OF SAMPLING REGIME

3.3.1 Benthic infauna sampling in each bay

The design of the sampling program was based primarily on the data needs of the carrying capacity model being applied to the Pied Oystercatcher. The area of intertidal habitat in each bay was mapped using Mean High Water Mark (MHWM) and Mean Low Water Mark (MLWM) polyline data provided by Land Information Services Tasmania, DPIW. The survey design in each bay was based on a grid arrangement, consistent with survey designs used in other wader carrying capacity modelling studies (e.g. West et al. 2006). A mixture of symmetric grids (i.e. square grid cells) and asymmetric grids (i.e. rectangular grid cells) and mixture of grid cell sizes was applied across the bays, depending on survey intensity and sample size assigned, and direction of tidal movement, as described below. Given the importance of the level of tidal immersion in determining invertebrate community composition, sampling was concentrated along the tidal gradient (i.e. more samples downshore than alongshore) where there was an obvious tidal gradient. In some bays, tidal flow direction is likely to be variable and a symmetric grid was justified. In each bay, grid intersection points that fell within the mapped area of sandflats between MHWM and MLWM polylines comprised invertebrate sampling sites, although Orielton Lagoon was an exception as outlined below.

In the absence of existing data on natural spatial and temporal variation in invertebrate communities in the bays of interest, this variability could not be considered during the design of the invertebrate sampling program. Instead, the number of samples that could be collected and processed by a field team of six staff during a one month period was first estimated, with consideration of potential weather interruptions, geographical locations of bays and logistical

8 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay issues associated with variable tidal conditions. These constraint attributes were identified on the basis of manageability of personnel and equipment, and temporal considerations of sampling. It was determined that, in the absence of information on spatial aspects of natural variability, duplicate samples would be collected per sampling site to account for small scale variation. The number and grid arrangement of samples to be collected in each bay were subsequently determined on the basis of total feasible sample size across all bays, collection of duplicate samples per site, and consideration of the additional factors outlined below:

• Total area of sandflat (from MLWM to MHWM): the size of the sandflat was estimated in each bay using polyline mapping data for MHWM and MLWM. This formed the initial basis of sample size allocation, with sample size proportional to the area of sandflat. However it was soon recognised that this resulted in allocation of very large samples sizes to some bays that included large areas of sandflat but were not necessarily important for high priority wader species or questions of the project. Sample sizes were therefore refined using the further considerations listed below. • Importance of the bay in terms of addressing the questions of the project: it was deemed that survey intensity would be greater at Lauderdale than the other sites, since the northern sandflat there represented the area to be affected by the proposed development. All estimates of foraging resources in other bays would be related back to the one estimate of what resources were being removed, and hence the latter estimate warranted greater survey intensity to maximise accuracy. • Importance of the area as a current foraging habitat: preliminary bird surveys had shown that some of the bays were not used by many waders for foraging and it can be assumed that the foraging resources are less available or suitable at these sites, although other factors may influence where birds feed. In areas that contain less invertebrate food, there is in all likelihood less variation in numbers of the relevant prey species, and hence fewer samples are required to achieve a comparable level of accuracy. • Questions being addressed by the survey in each bay: in all bays, there is the need to address the question of size of the foraging resource. In bays outside Lauderdale, there is no need to examine differences in foraging resources between sub-sections of bays or between habitats, since observations of the substratum in these bays revealed it to be relatively homogenous. However, at Lauderdale, there is also the question of foraging resources in the northern development zone versus those in the undeveloped more southern part of the bay. On this basis, the need for greater sampling intensity at Lauderdale was again highlighted. • Shape of the bay: Grid cell dimensions were also influenced by shapes of bays, since sampling intensity should be maximised with respect to the most important environmental gradient, tidal inundation. Therefore, for a long bay exposed to tidal movement primarily from one direction, it can be assumed that variation in invertebrate communities from one end of the bay to the other is small relative to variation between the high and low water marks. Therefore, grid cell dimensions between tidal marks were smaller than grid cell dimensions along the beach – i.e. an ‘asymmetric grid’ was adopted. This was applicable in particular to South Arm Neck, Five Mile Beach and Mortimer Bay. However for other bays where tidal flows were anticipated to be more complex, symmetric grids were adopted instead. • Combined shape and area of the bay: this was a consideration primarily for South Arm. Whilst it is an important foraging zone, its sheer size, combined with the relative homogeneity of habitats along much of the length of the bay and widely dispersed observations of birds feeding, suggested that a reduced sample number with relation to its size may achieve comparable accuracy of foraging resource estimates to those for other bays. • Reservation of samples for ‘additional’ non-grid sites: observations during the preliminary bird utilisation surveys (Aquenal 2008a) identified favourite wader feeding spots at some sites. It was recognised that information on favourite spots was based on a limited number of observations at that time and without the benefit of observations under all tidal conditions. It was therefore not considered appropriate to modify grids or stratify sampling within these areas, but instead, a small number of additional samples were allocated at these sites to facilitate foraging ecology studies. These sites were not used in quantitative estimation of foraging resources or as input for carrying capacity modelling, but more to inform the foraging ecology surveys. In addition to these foraging sites, it was recognised that the substratum at Lauderdale was less homogenous that in

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other bays. The northern flats include a range of rocky and soft sediment habitats, while the southern flats include a seagrass bed as well as unvegetated soft sediment habitats. It was also recognised that because the southern area was considerably smaller than the northern area, it would be useful to allocate some additional sampling sites to facilitate north versus south comparisons. On the above basis, some samples were reserved for comparisons of habitats and spatial zones at Lauderdale (see Section 3.3.2 below).

Applying the above factors, deviations from sample sizes being proportional to area of sandflat included a x3 weighting at northern Lauderdale (i.e. three times the level of survey intensity estimated on the basis of area of sandflat), x2 at southern Lauderdale, and x0.5 at both South Arm and Mortimer Bay. On this basis, numbers of sites for each bay were estimated and grids applied in MapInfo Professional© software whereby the number of grid intersection points overlaying the sandflat was approximately equivalent to the number of sites allocated to the bay using the above calculations.

It should be noted that at the time of planning the sampling design in accordance with the above approach, Carlton and Sorell Rivulet/Iron Creek were included in the program, but Orielton Lagoon was not, since preliminary wader surveys were still underway and the inclusion of the latter lagoon had not been confirmed. Orielton Lagoon was subsequently identified as an important wader site and added to the survey program, while Carlton and Sorell Rivulet/Iron Creek were removed from the program (see Aquenal 2008a). Initial observations suggested that the tidal zone at Orielton Lagoon was larger than indicated by available polyline data for MLWM. Hence, coarse tidal mapping was immediately performed to attempt to map the approximate position of the low water line, and the sampling grid was applied to the revised areal extent of tidal habitat mapped. Sampling intensity at Orielton Lagoon was applied at a x1 weighting based on area of sandflat.

Several adjustments were made to the survey program in winter 2007 to either increase the accuracy of estimates or extend the survey area, based on the results of detailed observations of waders foraging during the investigation of Harrison (2008). At Orielton Lagoon, observations during wader surveys suggested that there was a lag of approximately four hours between low tide in adjacent bays and low tide in the lagoon (R. Mawbey, pers. comm.). As a result of this and variation in low tide heights, the tidal mapping performed prior to spring 2006 survey work to revise the estimate of the tide zone area (due to the observed inaccuracy of the MLWM polyline) had still underestimated the extent of the tidal zone. The low tide mark was re-mapped on the basis of observations of feeding birds, and this line was used to extend the invertebrate sampling grid at Orielton Lagoon. At Barilla Bay, the allocated grid sites also missed one small area at the lower end of the tide zone that was important to birds, and hence the grid was extended to include this area. At Mortimer Bay, there had been a notable absence of the bivalve Anapella cycladea, a wader prey species found in all other bays. Since sampling intensity per area was reduced in Mortimer Bay (see above), it was important to ensure that this was not an artefact of sampling effort, particularly in higher parts of the shore which are generally favoured by A. cycladea. Hence, sampling intensity was increased during the final survey in winter at Mortimer Bay to target this prey species by expanding the existing network of grid sites and surveying additional nearshore sites.

In addition to the above extra sites surveyed in winter 2007, it was recognised that there was scope to allocate additional survey sites where needed to increase accuracy of estimates, particularly because of Carlton and Sorell Rivulet/Iron Creek being omitted from the sampling program after spring. As a result, sampling intensity was further increased at Lauderdale, with a second grid overlaid on the first which resulted in a doubling of the total number of grid survey sites.

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Note that at the majority of the new sites added to the survey program in winter, only one sample was collected instead of duplicates. This was due to initial analysis of the spring data by consultant statistician Glen Macpherson which revealed that replicates contributed a small proportion of variance in the dataset compared with sites. It was therefore preferable to maximise the number of additional sites surveyed rather than having a smaller number of new sites with duplicate samples.

A summary of the numbers of sites surveyed in spring/summer and winter are indicated below in Table 3, including sites located using grids and the additional sites surveyed to collect data from observed wader feeding spots or additional habitats and survey zones at Lauderdale.

Table 3 Numbers of sites and samples in each bay for grid sampling designs and additional areas surveyed to target specific habitats (and survey zones, Lauderdale).

SPRING/SUMMER No. grid sites No. extra sites Total sites BAY (No. samples) (No. samples) (No. samples) Lauderdale 40 (80) 25 (50) 65 (130) Mortimer Bay 10 (20) 2 (4) 12 (240 South Arm 22 (44) 0 (0) 22 (44) Pipeclay Lagoon 32 (64) 1 (2) 33 (66) Five Mile Beach 14 (28) 1 (2) 15 (30) Barilla Bay 22 (44) 0 (0) 22 (44) Orielton Lagoon 13 (26) 0 (0) 13 (26) TOTAL 153 (306) 29 (58) 182 (364) WINTER No. grid sites No. extra sites Total sites BAY (No. samples) (No. samples) (No. samples) Lauderdale 81 (121) 25 (50) 106 (171) Mortimer Bay 20 (30) 5 (10) 25 (40) South Arm 22 (44) 0 (0) 22 (44) Pipeclay Lagoon 32 (64) 1 (2) 33 (66) Five Mile Beach 14 (28) 1 (2) 15 (30) Barilla Bay 25 (50) 0 (0) 25 (50) Orielton Lagoon 34 (47) 0 (0) 34 (47) TOTAL 228 (384) 32 (64) 260 (448)

Information sought from benthic infauna samples was three-fold in terms of generating data required for the Pied Oystercatcher carrying capacity model:

• Species composition and abundance per sample, to assess the density of prey species. This was analysed in all samples collected (note that species composition and abundance was also recorded to allow subsequent interpretation of prey data relevant to other wader species). • Size measurements of prey species, so that density estimates in (1) above could be limited to invertebrates within the size range preyed upon by waders [based on the study of Harrison (2008)], and that size could also be used in estimating the total foraging resource in conjunction with (1) above and (3) below. Individual sizes of prey species were measured in all samples collected. • Ash Free Dry Mass (AFDM) of prey species individuals, so that the total biomass of the foraging resource could be estimated in conjunction with (1) and (2) above. Since AFDM specimens needed to be preserved differently from the samples collected for (1) and (2) (see Section 3.4.1), additional samples were collected for AFDM

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analysis and were obtained from approximately every second invertebrate sampling site in each bay. This ensured that AFDM estimates were not biased by prey attributes in any one particular area of the sandflat.

During the first survey performed in spring 2006, sediment samples were also collected for physico-chemical analysis to characterise the environment of the sandflats and facilitate the interpretation of invertebrate data. Variables recorded included redox potential, particle size distribution and a sediment description (see Section 3.5 below). Sediment surveying was conducted at approximately every second invertebrate sampling site. It was not necessary to repeat the sediment sampling during subsequent surveys, since seasonal variation was not anticipated in the sediment variables being measured.

Note that detailed tidal mapping was conducted in each bay to provide sandflat exposure data for the Pied Oystercatcher carrying capacity model, with the methodologies described by Atkinson and Stillman (2008). One dataset generated by this work, which provides adjusted heights to the Port of Hobart chart datum for the benthic infauna sampling sites, was used in the current study to assess variation in prey resources associated with tide height. On the basis of the heights of the highest and lowest sites recorded across the entire study area, four levels of tide height each encompassing an equivalent portion of the total tide height range were categorised, with 1 representing the area highest on the shore (i.e. inundated for the shortest length of time) and 4 representing the area lowest on the shore (i.e. inundated for the greatest length of time).

The grid overlays and sampling sites allocated at Lauderdale are illustrated in Figure 3 (northern end) and Figure 4 (southern end), while maps showing sampling sites in other bays are included in Figure 5 through to Figure 10. MLWM is indicated in each figure on the basis of DPIW polyline data. A key to site colour symbols for the maps is included in Table 4 and indicates sites sampled for AFDM and sediment physico-chemical variables, as well as for generic invertebrate attributes (i.e. density and size of prey species). It also indicates the additional sites sampled during winter and those surveyed at Lauderdale to facilitate habitat and north versus south comparisons. Geographical coordinates for survey sites were recorded in the projection WGS84 using a Garmin GPS unit accurate to ~ 5 m. Geographical coordinates for all sampling sites are included in Appendix 1.

Table 4 Site symbols in benthic infauna sampling maps for Lauderdale and other bays.

Symbol Samples collected All bays: Duplicate invertebrate samples in spring, summer and winter. All bays: Duplicate invertebrate samples in spring, summer and winter; sediment core samples in spring; Ash Free Dry Mass (AFDM) samples in spring, summer and winter. Lauderdale: Duplicate invertebrate samples in spring, summer and winter; extra habitat sites. Lauderdale: Duplicate invertebrate samples in spring, summer and winter; extra tide zone sites. Other bays: Individual or duplicate (sites 23, 25) invertebrate samples in winter at Mortimer Bay (additional winter sites); AFDM samples in winter. Lauderdale: Individual invertebrate sample in winter (additional winter sites). Other bays: Duplicate (Barilla Bay) or individual (Orielton Lagoon, Mortimer Bay) invertebrate samples in winter (additional winter sites). Lauderdale: Individual invertebrate sample in winter; AFDM samples in winter (additional winter sites). Other bays: Duplicate (Barilla Bay) or individual (Orielton Lagoon, Mortimer Bay) invertebrate samples in winter; AFDM samples in winter (additional winter sites). All bays: Duplicate invertebrate samples in spring, summer and winter; wader foraging site identified in preliminary bird utilisation surveys.

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5

4 42 66 41 3 67

2 68 45 9

1 69 44 8 70 47 43 48 7 71 46 13 63 49 6 72 59 12 74 61 64 73 11 75 62 HABITAT KEY 10 76 17 60 Dense rubble 77 16

Sand/rock 78 15 79

14 80 Sand/pebbles 21

81 20

19 82

18 83 25 84  0 150 300 24 85 metres 23 86

22 87 29

Figure 3 Intertidal benthic infauna sampling sites and habitats at Lauderdale (northern half).

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22 87 29 88 28 89 27 90

26 91

92 31

30

93

94

32 HABITAT KEY 95

96 Seagrass

33

97 98 65 53 34 99 57

100  54 37

101 36 0150 300 55 35 58 metres 102 50 51 56 103 40 52 104 39

38 105

106

Figure 4 Intertidal benthic infauna sampling sites and habitats at Lauderdale (southern half).

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Figure 5 Intertidal benthic infauna sampling sites at Barilla Bay.

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Figure 6 Intertidal benthic infauna sampling sites at Five Mile Beach.

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Figure 7 Intertidal benthic infauna sampling sites at Mortimer Bay.

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Figure 8 Intertidal benthic infauna sampling sites at Orielton Lagoon.

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Figure 9 Intertidal benthic infauna sampling sites at Pipeclay Lagoon.

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Figure 10 Intertidal benthic infauna sampling sites at South Arm.

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3.3.2 Additional benthic infauna sampling at Lauderdale

Additional invertebrate sampling was conducted at Lauderdale to facilitate inter-habitat and north-south comparisons. The northern section of the Lauderdale sandflat at the proposed development site is unique in providing a range of rocky substrata in addition to the more widespread sandy substratum. Discussions with consultants involved in the preliminary bird utilisation surveys (Aquenal 2008a) indicated that waders did feed amongst these rocky habitats and that it was possible that they contained different food resources to the sandy areas. Aquenal therefore mapped these areas on foot with the assistance of a handheld GPS unit to delineate boundaries for areas of dense rubble, sand with intermixed pebbles, and sand with intermixed medium/large rocks (Figure 3). Similar mapping was conducted for a sparse seagrass patch located at the southern end of the Lauderdale sandflat (Figure 4), as this provided yet another habitat type that was potentially differentiated on the basis of wader foraging resources.

It was noted that the uniform grid design first applied in spring 2006 and described in Section 3.3.1 had allocated small and variable numbers of sites in these rocky and seagrass habitats at Lauderdale: zero samples in dense rubble, one in sand/intermixed pebbles, two in sand/intermixed rocks, and one in seagrass. In order to provide representative data for these habitats, additional sites were allocated so that four survey sites (= eight samples), incorporating any sites allocated using the uniform grid design, were collected during each sampling event from each rocky habitat type and from the seagrass patch. Extra sites selected to make up the four sites in each habitat were positioned on the basis of mapped habitat boundaries to give even spatial coverage of the respective habitat.

An important element of the wader studies at Lauderdale was to characterise any differences in bird utilisation and feeding patterns, and associated invertebrate communities, between the northern proposed development site and the more southern sandflats at Lauderdale. A number of survey zones were identified on the Lauderdale sandflats for the bird utilisation and foraging studies (Aquenal 2008a, Harrison 2008) and also formed the basis of spatial comparisons of invertebrate assemblages at a community level (Aquenal 2008b) and as wader foraging resources in the current report. While the bird survey areas at Lauderdale consisted primarily of five zones (and a mussel/oyster survey zone; refer to Figure 15 in Section 3.3.4) that were applied to model inputs for the Pied Oystercatcher carrying capacity model, these were summarised to three zones for the purpose of more descriptive analyses of spatial variation at Lauderdale: N1 corresponds to the majority of the proposed development site (patches 1 and 2, Figure 15f); N2 is the area to the south of N1 that is still north of the southern narrow channel (patch 3, Figure 15f); and S is the southern part of the sandflats (patches 4 and 5, Figure 15f) (Figure 11). Note that the boundary between N1 and N2 was devised at the start of the sampling program and represented the southern proposed boundary of the development at that time. The site plan for the development has since been revised, as reflected in Figure 1, and includes further development and a southern channel that extend the total disturbance zone south of the N1/N2 boundary, as shown in Figure 11. This extension is addressed in the carrying capacity report of Atkinson and Stillman (2008) to ensure that carrying capacity modelling incorporated the most up to date total disturbance zone.

The above uniform grid system allocated sites to the N1, N2 and S zones, however site numbers were relatively low in S, particularly before sampling intensity was increased in winter. It was therefore determined in consultation with statistician Glen Macpherson that additional sites would be sampled to supplement grid sites and facilitate north- south comparisons, and that the sites allocated would be comparable between the north and south in major environmental attributes such as substratum type.

Additional sampling to facilitate north-south comparisons was therefore restricted to the sandy substratum that was present at northern and southern ends of the sandflat, while initial tidal mapping was performed to identify zones of variable immersion times. Detailed tidal mapping was subsequently conducted at Lauderdale to provide sandflat exposure data needed for the Pied Oystercatcher carrying capacity model (as referred to above in Section 3.3.1), but these data were not available during the invertebrate sampling program. Tidal mapping was therefore performed on

21 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay foot with the assistance of a handheld GPS unit to map the boundary of ankle deep water (since it was estimated at the time that this was the maximum water depth at which Pied Oystercatchers could continue feeding) at hourly intervals after low tide at the north end, and hourly intervals before low tide at the southern end, over the course of one day. Based on this, it was identified that tidal zones exposed at 1, 2 and 3 hours from low tide each included large areas of sandy habitat at both the northern and southern ends, although the exposed area comprised a smaller portion of the northern sandflat due to its lower mean shore elevation. Two sites, with duplicate samples each, were placed in each of these three tidal zones in N1 and in S (i.e. six sites comprising 12 samples in each of N1 and S). Additional sites were not allocated at N2, since the main focus was to compare foraging resources between the development site and the southern area of sandflat that was least likely to be affected by disturbance at the development site. Sites in each tidal zone in N1 and S were selected randomly using a combination of mapping grids and the Microsoft®-Excel© randomisation function.

Figure 11 Map indicating the boundaries of survey zones N1, N2 and S (bold black lines) at Lauderdale, and the outline of the development disturbance area (red line). Grids and locations of survey sites are also indicated.

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3.3.3 Epibenthic sampling at Lauderdale, Pipeclay Lagoon and South Arm

The native blue mussel Mytilus galloprovincialis and Pacific oyster Crassostrea gigas form epibenthic clumps in localised areas and are not targeted by routine benthic invertebrate coring methods. However, bird foraging surveys by Harrison (2008) suggested that these species were important prey for Pied Oystercatchers at Lauderdale, Pipeclay Lagoon and South Arm. It was therefore necessary to survey mussels and oysters in these areas to supply prey resource data for the Pied Oystercatcher carrying capacity model. The mussel and oyster foraging areas in these three bays were initially mapped coarsely on the basis of wader feeding observations, and were subsequently mapped in more detail by subconsultant Ron Mawbey and an Aquenal staff member on 10th July 2007.

For each of the three survey areas (one per bay), grids were inserted as overlays in maps generated by MapInfo Professional©. Grid cell dimensions of 20 m x 20 m were applied, with grids rotated so that one set of grid lines was approximately parallel to the anticipated primary direction of tidal movement. These grids were used to determine the positions of survey transects, with the grid intersection points closest to the boundaries of (but within) the mapped oyster/mussel feeding area representing the transect start and end points. The transect lines were drawn along the grid lines parallel to the direction of tidal movement. On the basis of the above grid cell size, transects were separated by 20 m. The locations of the survey areas and transects in the three bays are illustrated in Figure 12 through to Figure 14.

As described in Section 3.1, oyster and mussel data could not be collected to the same seasonal design as benthic infauna species due to their identification as a prey resource in the late stages of the invertebrate sampling program. These data provide useful input to the Pied Oystercatcher carrying capacity model by allowing oysters and mussels to be included in prey resource estimations, including modelling of the reduction of resources that could result from removal of the mussel/oyster patch on the northern Lauderdale sandflat. However, seasonal changes in contributions of oysters and mussels to the total prey resource cannot be estimated on the basis of data collected, necessitating the assumption that this contribution remains seasonally constant.

3.3.4 Identification of ‘patches’ for the Pied Oystercatcher carrying capacity model

The Pied Oystercatcher carrying capacity model incorporates data for a number of distinct ‘patches’ within the survey area. These patches are frequently determined on the basis of habitats and distributions of main prey species. However, given that it is necessary to have bird count, foraging observations and invertebrate data for each patch, the boundaries of patches in the current study were determined to a large extent on the basis of zones that were practical for the purpose of recording bird counts and foraging observations. Bird counts were conducted during the wader utilisation surveys (Aquenal 2008a) and during the foraging ecology observations (Harrison 2008), and provide data for two sets of patches. During the bird utilisation surveys, bird counts were pooled for the entire sandflat area in each bay except at Lauderdale and Pipeclay Lagoon, while Harrison (2008) recorded counts for a larger number of zones in most bays during the foraging ecology surveys, with these zones illustrated in Figure 15. The wader utilisation surveys pooled counts for zones 1 and 2 and for zones 4 and 5 at Lauderdale, for zones 1 and 2 at Pipeclay Lagoon, and pooled all zones in the remaining bays. Counts were recorded only at a ‘bay’ level at Orielton Lagoon and Five Mile Beach in both studies, and hence only one zone is indicated for each of these areas in Figure 15. The survey zones in each bay constitute ‘patches’ for the model, with both the Aquenal (2008a) and Harrison (2008) datasets incorporated in the modelling. Note that the central section of Pipeclay Lagoon categorised as patch 5 in Figure 15g was not surveyed for birds; however invertebrate data were collected in this area and provided as supplementary model input.

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LT-1-1 01530 LT-2-1 metres

LT-3-1

LT-4-1

LT-1-2

LT-5-1 LT-2-2

LT-3-2

LT-4-2 LT-5-2

Figure 12 Location of the mussel and oyster foraging area at Lauderdale (top; indicated by the black box) and position of epibenthic survey transects positioned within it (bottom).

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01530 PT-1-1 metres PT-2-1 PT-3-1

PT4-1 PT-1-2

PT-2-2

PT-3-2 PT-4-2

Figure 13 Location of the mussel and oyster foraging area at Pipeclay Lagoon (top; indicated by the black box) and position of epibenthic survey transects positioned within it (bottom).

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ST-1-1 ST-5-1 ST-2-1 ST-6-1

01530 metres

ST-3-1

ST-4-1 ST-7-1

ST-8-1

ST-1-2

ST-2-2

ST-5-2 ST-3-2 ST-7-2 ST-6-2 ST-4-2 ST-8-2

Figure 14 Location of the mussel and oyster foraging area at South Arm (top; indicated by the black box) and position of epibenthic survey transects positioned within it (bottom).

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a) b)

c) d)

e) f) g)

Figure 15 Distributions of survey zone ‘patches’ in each bay: a) Five Mile Beach; b) Mortimer Bay; c) Barilla Bay; d) South Arm; e) Orielton Lagoon; f) Lauderdale; and g) Pipeclay Lagoon. A 500 m scalebar has been included in the map for each bay.

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The mussel/oyster survey zones described above in Section 3.3.3 also provide distinct prey resources within clearly mapped areas and hence can be included as separate patches in the carrying capacity model. Bird count and foraging data were collected in these zones by Harrison (2008).

As described in Section 3.5.3.1 below, invertebrate data providing input for the Pied Oystercatcher carrying capacity model were processed to link sampling sites with the individual ‘patch’ in which they were located.

3.4 FIELD SURVEY METHODOLOGY

3.4.1 Benthic infauna field sampling

Benthic infauna communities occupying shallow intertidal sediments were surveyed in each bay. Mapping was conducted initially to generate Global Positioning System (GPS) coordinates for each sampling site and these coordinates were downloaded to GPS units prior to field survey work to enable field personnel to readily identify site locations. It was not feasible to survey the large number of allocated sites at a uniform tidal phase, therefore field techniques consisted of a mixture of sampling of dry or shallow sites on foot (i.e. sites not tidally immersed or immersed up to a depth of ~ 50 cm; the primary method applied) and sampling of more deeply immersed sites with the help of snorkel gear. Care was taken to avoid conscious or unconscious bias when placing the corer. This was achieved by collecting the first sample at the tip of the toe after the last pace when accessing the site on foot, or in the first patch of sediment viewed when snorkelling down to the seabed, and then collecting the second core 1 m from the first in line with the orientation of the transect. Transect lines were not deployed in the field to connect the grid sites, however the orientation of these ‘imaginary’ transect lines was apparent on the GPS units used. Note that two sites needed to be re-located in Pipeclay Lagoon due to their locations overlapping with the positions of shellfish farming structures. In these instances the site was relocated to the nearest area of intertidal habitat that could feasibly be surveyed.

At each sampling site, benthic infauna samples were collected and processed as follows:

• Benthic infauna sediment core samples were collected using a tubular 0.025 m2 (17.9 cm internal diameter) hand corer to a depth of 15 cm, the maximum depth that could be sampled using this coring apparatus. While intertidal benthic infauna species primarily occur in the top 10 cm of sediments, especially where conditions become anoxic at this depth (see Section 4.1), sampling was conducted deeper to collect any species potentially migrating further into the sediment. It was considered important to sample the full depth range for benthic infauna species given that sampling was conducted at various phases of the tide, and hence species that perform vertical migrations in relation to tidal movement could have occupied variable sediment depths during the course of sampling.

• Samples were immediately transferred to individually labelled 800 µm mesh bags, rinsed in seawater to remove some of the finer sediment in the bag and placed in drums of 10% buffered formalin. During the winter 2007 survey, an alternative field processing technique was used whereby the samples were emptied from corers into individual nally bins and then sieved in the field using 4 mm and 1 mm sieves in order to extract worms from remaining material. Samples were subsequently placed in individually labelled plastic vials containing 10% buffered formalin, with the extracted worms kept separate from the remainder of the sample. This alternative technique was used in an attempt to reduce the occurrence of fragmented worms in the samples through crushing, since it was important to measure lengths for wader prey species such as polychaete worms.

At each physico-chemical sediment analysis site, samples were collected and processed as follows:

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• During the spring 2006 survey, one additional core sample was collected at each designated physico-chemical sediment analysis site using a 45 mm diameter, 20 cm length transparent Perspex tube. The tube was pushed into the sediment to the maximum depth feasible, with core sample length dependent on the level of consolidation of the sediments. Cores were sealed and individually labelled, kept upright and placed in core holders prior to being processed.

• Cores were transported to a processing station erected in the field and each core was described in relation to colour, texture (e.g. sand, mud), hydrogen sulphide odour, and the presence of flora and fauna.

• Within one hour of collection, each core was analysed in the field for redox potential using a WTW pH 320 meter with a Mettler Toledo Ag/AgCl combination pH / Redox probe. Measurements were taken at core depths of 1 cm, 4 cm and 10 cm (or deepest section for cores less than 10 cm length). The standard potential of the Ag/AgCl reference cell of the probe is 218 mV at 10°C, the approximate temperature of the samples during measurement. Calibration and functionality of the meter were checked before each test using a Redox Buffer Solution (220 mV at 25 °C). Corrected redox potential values were calculated by adding the standard potential of the reference cell to the measured redox potential and are reported in millivolts.

• The core sample was extruded, homogenised through mixing and used to fill a plastic 77 ml vial. This sample was used for subsequent analysis of particle size distribution in the laboratory.

• Note also that additional sediment samples were collected at Lauderdale in spring 2006 to conduct preliminary analyses of heavy metal concentrations, and more detailed analyses of particle size distributions (i.e. fractions measured down to 0.2 µm) in shallow intertidal sediments. This sampling was conducted opportunistically to contribute to assessments of sediment characteristics and quality being performed for other aspects of the Lauderdale Quay IIS. Results are reported by Technical Advice on Water (2007) and are not included in the current report.

At each Ash Free Dry Mass (AFDM) invertebrate sampling site, AFDM samples were collected and processed as follows:

• At each designated site, two tubular 800 µm mesh bags of dimensions 15 cm diameter x 30 cm length were filled with sediment using a small shovel. Sediments were collected to a depth of ~ 15 cm and a waterproof label was included in each sample indicating the site number.

• A field sample processing station was established and the above samples were sieved using 4 mm mesh to extract benthic infauna wader prey species within the prey size ranges determined from observations during the foraging ecology field studies of Harrison (2008) (see Section 3.5.1 below).

• Polychaete individuals extracted from sediment samples were classified in the field according to species denoted by species number (e.g. polychaete 1, polychaete 2) and the length of each individual was measured to the nearest millimetre. Measuring was conducted whilst in the field, since the subsequent process of freezing animals had the potential to distort length measurements. Each individual was then placed in its own zip lock bag and labelled with site number, species number and length. Mollusc species were also classified according to a species number, but were not measured in the field because their lengths are not affected by freezing. All individuals belonging to each mollusc species collected from each site were placed together in a zip lock bag, since in the absence of field measurements it was not necessary to identify individuals prior to laboratory

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analysis. Bags were labelled with site and species number information, and samples of all polychaetes and molluscs were placed on ice prior to subsequent storage at -20ºC in a laboratory freezer.

The aim was to collect at least 21 (the batch number for processing AFDM samples in the furnace) individuals per prey species per bay that covered the full dietary size range of animals found in the samples. While many more than 21 were processed in the field for certain species, a subset of samples was selected for laboratory analysis as described in Section 3.5.1.

3.4.2 Epibenthic fauna field sampling

Epibenthic mussels and oysters were surveyed on transects positioned according to the methods described in Section 3.3.3. Geographical coordinates for transect start and end points were downloaded to a GPS unit to enable transects to be readily located and a 8 mm width transect line labelled at 5 m intervals was used to mark the position of each transect survey area on the sandflat.

On each transect, counts of oysters and mussels were made for every second 5 m section (i.e. 0-5 m, 10-15 m, 20-25 m, 30-35 m), so that approximately one half of the transect length was surveyed overall. In each 5 m section surveyed, the area surveyed extended 1.5 to either side of the transect line, so that the total survey area in that 5 m section was 5 m x 3 m (15 m2). In every second 5 m section surveyed for mussel and oyster abundance (i.e. 10-15 m, 30-35 m, 50-55 m, 70-75), these species were measured as well as counted. The total length at the maximum dimension of each individual mussel and oyster was measured using vernier callipers and recorded to the nearest mm.

Since the mussel/oyster beds consisted only of the oyster Crassostrea gigas and mussel Mytilus galloprovincialis, there was no need to collect samples for the purpose of identification and specimens were returned to their original site once measured, whilst counting occurred in situ.

Samples of mussels and oysters were collected for AFDM analysis. Only individuals in the size range consumed by waders (Table 1) were collected for this analysis. A minimum of 50 mussels and 50 oysters were collected per bay and included specimens from each transect surveyed to ensure that analyses were not biased by the prey attributes in any one particular section of the oyster/mussel beds. Specimens were placed in zip lock bags labelled with the bay, transect number and transect interval and placed on ice. These samples were subsequently returned to the laboratory and placed in a freezer at -20ºC.

3.5 LABORATORY AND ANALYTICAL METHODS

Samples were processed to compile data on numbers and distributions of prey species relevant to Pied Oystercatchers and other waders, with sediment samples processed to assist with the characterisation of the environment and interpretation of the prey density data. Further sample analyses to compile data on sizes and Ash Free Dry Masses (AFDMs) of prey species were conducted specifically to provide input to the carrying capacity model for the Pied Oystercatcher.

3.5.1 Benthic infauna samples

Invertebrate core samples were returned to the laboratory and, following a minimum fixation period of two days in formalin, were sieved using 4 mm and 1 mm mesh to remove fine sediments. Remaining material was sorted under a dissecting microscope to separate animals from shells and other material. Animals were placed in labelled vials

30 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay containing 70% ethanol and were subsequently counted and identified to species level, or the closest possible taxonomic unit, under a dissecting microscope. The above procedure was repeated minus the sieving component for the winter 2007 samples which had already been processed using 4 mm and 1 mm sieves in the field. Individuals of bivalves, polychaetes and the gastropod Salinator fragilis were subsequently measured to record their lengths to the nearest mm, with S. fragilis individuals only measured in samples collected from the areas outlined in Section 3.2.1.

For the spring 2006 samples that were collected prior to the foraging surveys of Harrison (2008), a conservative approach was applied whereby all individuals with a minimum length of 5 mm were measured, since this was considered smaller than the likely size of animals consumed by waders. This approach was also adopted for the summer 2007 samples, however it subsequently became clear that for the prey species being targeted in the current benthic infauna sampling program, the birds were feeding on very few prey items < 10 mm length. Hence only individuals 10 mm or larger were measured in the winter 2007 invertebrate samples. For polychaetes and bivalves, the maximum length was recorded. The length of the gastropod Salinator fragilis was measured from the shell apex (protoconch) through to the base of the body whorl.

Sediment samples retained for particle size analyses were processed in the laboratory. For each sediment sample, the sample volume was measured by emptying it into a measuring cylinder containing 20 ml of water and noting its displacement volume. The material was then washed through a stack of sieves using a moderate water spray. The sieve aperture sizes used were 2 mm, 500 µm and 63 µm, corresponding to material coarser than sand (e.g. pebbles, shells), coarse sand and fine to medium sand, with the volume washed through the finest sieve corresponding to silt/clay. While a larger number of sieve aperture sizes are sometimes used in benthic infauna studies, the above were considered adequate for identifying major patterns of variation in particle size contributions. Sediments retained in the sieves were transferred sequentially to a measuring cylinder containing 20 ml of water and their cumulative displacements measured. The percentage by volume of each fraction was then calculated for the original sample. The combined percentage of measured fractions was subtracted from 100 to give the percentage of the <63 µm fraction.

Ash Free Dry Mass (AFDM) samples were processed to compile data for 21 individuals (based on furnace capacity, see Section 3.4.1) per major prey species in each bay and season where feasible. The species analysed included the bivalves Anapella cycladea and Katelysia scalarina, and the polychaetes Nephtys australiensis, Leitoscoloplos normalis and Olganereis edmonsi. The gastropod Salinator fragilis was also analysed from areas where it had been observed to be an important prey item. For species represented by more than 21 individuals in field samples, a subset of samples was selected for analysis that provided maximum coverage of the survey area and full representation of the dietary size range for Pied Oystercatchers. Species were identified in the laboratory to convert species numbers recorded in the field to full taxonomic identifications. While polychaetes had been measured in the field, the molluscs had not and so their lengths were measured to the nearest mm prior to further processing. Each specimen was allocated a label for individual identification.

Ceramic crucibles were used to contain samples being processed for AFDM. Crucibles were marked with an individual label for identification purposes and placed in a drying oven at 90oC for one hour to remove all moisture. After cooling in a dry environment, the crucible weights were measured to an accuracy of 0.1 mg. One frozen polychaete or mollusc specimen was added to each crucible with corresponding specimen and crucible labels recorded. Molluscs were allowed to partially thaw in the crucible and then had all flesh removed from the shell whilst containing any lost body fluids within the crucible. Shells were removed and not included in subsequent processing. The crucibles containing the wet polychaete and mollusc individuals were again weighed to an accuracy of 0.1 mg, a weight referred to as the ‘crucible + wet flesh weight’. Crucibles containing wet specimens were then placed in a drying oven at a temperature of 90oC for four hours. In trials that extended for longer periods, no further decline in weights was recorded after four hours and hence this period of drying was considered adequate. The crucibles with dry specimens were placed in a dry environment to cool sufficiently to enable handling and then were

31 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay re-weighed to an accuracy of 0.1 mg. The resulting weight was referred to as the ‘crucible + dry flesh weight’. Crucibles containing the dry specimens were next placed in a muffle furnace at 580oC for four hours. In trials, this period of time was found to be adequate to achieve constant weight. After again cooling in a dry environment, weights of the crucibles containing ash were recorded to an accuracy of 0.1 mg. This weight was referred to as ‘crucible + ash weight’. ‘Crucible + ash weight’ was subtracted from ‘crucible + dry flesh weight’ to estimate the AFDM in mg.

3.5.2 Epibenthic fauna samples

Laboratory analyses for epibenthic mussels and oysters were limited to AFDM analyses. Methods applied were the same as those described in Section 3.5.1 above for benthic infauna, with the exception that samples spent ten hours instead of four hours in the muffle furnace. Trials revealed that a longer period was required in the furnace before weight remained constant, the result of the mussel and oyster specimens being larger than those of benthic infauna prey species.

3.5.3 Data analyses

3.5.3.1 Data input for the Pied Oystercatcher carrying capacity model

The primary application for invertebrate data collected was to provide input for the Pied Oystercatcher carrying capacity model which requires data on prey resources within the foraging grounds of this wader species. Information on prey resources was developed in conjunction with information on prey items consumed by Pied Oystercatchers (Harrison 2008), as described in Section 3.2.1. Note that only data collected at the invertebrate grid sites were included as model input.

The key data for the model were numbers of each prey item per invertebrate sample that fell within the size range consumed by the birds. It was determined that, on the basis of very low numbers of items < 10 mm length in the Pied Oystercatcher diet, that 10 mm was the lower size limit for model input relating to benthic infauna prey species (i.e. bivalves, polychaetes and the gastropod Salinator fragilis). While the minimum size of consumed prey was larger than 10 mm for some species (see Table 1), this generally applied to less common prey types that were recorded from a small number of observations. The smaller minimum sizes recorded from a large number of observations for common prey types are considered more applicable. There was no clear evidence of birds rejecting any of the benthic infauna prey items above a maximum size, hence all prey items above 10 mm were included.

All bivalves and polychaetes ≥ 10 mm in the benthic infauna samples were included in the carrying capacity modelling data input. In the case of bivalves, this included the main prey species Anapella cycladea and Katelysia scalarina, other less common clam-like bivalves observed during foraging surveys to be consumed by Pied Oystercatchers (see Table 1), and additional bivalves that were not recorded in the diet but are likely to contribute to the prey resource on the basis of shell type and size (this only included occasional Paphies erycinea and Theora lubrica). In the case of polychaetes, which could not be identified to species level during the foraging surveys, the common species in the invertebrate samples - Nephtys australiensis, Leitoscoloplos normalis and Olganereis edmonsi - were included as well as 25 other less common species that recorded individuals ≥ 10 mm. For gastropods, only Salinator fragilis was included since there are many other gastropods present on the sandflats, but only S. fragilis was confirmed as a prey item. This may be related to the thin shell of this species and relatively large soft tissue: shell mass ratio, while gastropod species with thick shells are less likely to be suitable as prey.

32 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

For the larger epibenthic prey species Crassostrea gigas (Pacific oyster) and Mytilus galloprovincialis (blue mussel), minimum and maximum sizes were applied since the birds were observed feeding on individuals 30-69 mm in the case of C. gigas and 22.7-82 mm for M. galloprovincialis. To align with size classes incorporated in the model, the size range of M. galloprovincialis included was adjusted slightly to 20-85 mm. The birds were seen to visibly reject oysters and mussels that were larger than the above maximum sizes.

The model calculates prey resource on the basis of mass. Therefore, for each prey item, the size categories needed to be related to a mass in order to estimate the foraging resource. The AFDM data collected for the main prey species was used for this purpose. AFDM was not calculated for each of the rarer bivalve and polychaete species due to difficulties obtaining sufficient specimens across the size ranges present to compile AFDM versus length relationships. Hence, in the density/size data set, each less common bivalve was pooled with either Anapella cycladea or Katelysia scalarina, while each less common polychaete was pooled with one of Nephtys australiensis or Olganereis edmonsi. This was conducted by pooling data for each less common species with data for the common species that shared the most similar expected AFDM/length relationship on the basis of shape. In some cases, shapes were highly variable, but pooling was conducted on the basis of the most similar species feasible. Table 5 outlines which less common species were pooled with each of the common ‘main prey’ species. Note that separate AFDM/length data had been obtained for the common species Nephtys australiensis and Leitoscoloplos normalis, which have similar body shapes. Hence similar less common species could have been pooled with either of these species but were pooled with N. australiensis, since it is likely that the AFDM/length relationship was estimated more accurately for this species due to its lower susceptibility to fragmentation in the samples.

In the case of the gastropod Salinator fragilis, oyster Crassostrea gigas and mussel Mytilus galloprovincialis, AFDM had been obtained for each of these species and no other similar species were pooled with these prey types.

For each benthic infauna core grid sample collected, animals for each of the six prey type categories (i.e. the four main prey groups in Table 5 plus Salinator fragilis and Leitoscoloplos normalis) were allocated to 5 mm size classes: 10-14 mm, 15-19 mm, 20-24 mm and so forth. Each prey type/size class combination was identified in model input as a separate prey resource type, categorised according to an alphanumeric label. For example, A1 referred to the Anapella cycladea group in the size range of 10-14 mm, while K2 referred to the Katelysia scalarina group in the size range of 15-19 mm. Note that a size class such as 10 -14 mm included all animals of lengths 10 mm through to < 15 mm (i.e. ≤ 14.9 mm based on measurements to a 0.1 mm accuracy).

For the epibenthic species Crassostrea gigas and Mytilus galloprovincialis, data was collected within 5 m intervals along transects, as outlined in Section 3.4.2. For each transect, size measurement data were available for between one and four 5 m x 3 m (15m2) survey areas, depending on transect length. Size data were therefore prepared for each of these survey areas, with oysters and mussels allocated to 5 mm size classes. As described above for benthic infauna species, resource types were categorised according to an alphanumeric label. For example, M1 referred to M. galloprovincialis in the size range of 20-24 mm, while C2 referred to C. gigas in the size range of 35-39 mm.

Data on invertebrates provided as input to the model were categorised according to bay (e.g. Lauderdale, Mortimer Bay), season (spring, summer, winter), patch as illustrated in Figure 15, sampling station (site/transect number), sample (core/transect interval number) and resource type (e.g. A1, K2; as described above). The number of invertebrate sampling stations in each patch and total patch area were also included as model input in conjunction with the invertebrate data.

The AFDM measurements were provided as a separate dataset to provide input for the model, with the information provided for each individual analysed including: species, AFDM (mg), length (mm), bay, season, patch and

33 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay sampling station. Further information on the processing of the AFDM and other invertebrate data for the Pied Oystercatcher carrying capacity model is provided in Atkinson and Stillman (2008).

3.5.3.2 Descriptive statistics

Whilst the invertebrate data were collected primarily as input for the Pied Oystercatcher carrying capacity model, survey results are described in the current report to summarise trends in the distribution, composition, density and size of prey species for Pied Oystercatchers, as context for the above model, and for other waders.

Table 5 Less common bivalve and polychaete species pooled with main prey species for model input.

Main prey species Anapella cycladea Katelysia scalarina Nephtys australiensis Olganereis edmonsi Less common species pooled with the above main prey species Laternula tasmanica Soletellina biradiata Capitella sp. Australonereis ehlersi Wallucina assimilis Tellina deltoidalis Barantolla lepte Phyllodoce sp. Eumarcia fumigata Goniada sp. Neanthes vaalii Paphies erycinea Glycinde sp. Neanthes sp. Theora lubrica Sabellid sp. Malacoceros tripartitus Lumbrineris sp. 1 Harmothoe sp. Lumbrineris sp. 2 Pectinaria sp. Asychis sp. 1 Asychis sp. 2 Micromaldane sp. Boccardia polybranchia Prionospio ?wambiri Carazziella victoriensis Spio pacifica Cirratulid sp. Magelona sp. Abarenicola affinis Euzonus sp. Armandia sp. Pectinaria sp.

Detailed univariate analyses testing statistical significance of differences in individual prey variables (e.g. density, size) were not performed, since it is the combination of these variables that, in conjunction with sandflat exposure and other variables, define the foraging resource. The carrying capacity model of Atkinson and Stillman (2008) considers all of these variables and therefore provides a more appropriate and comprehensive analysis of invertebrate data as it relates to the total foraging resource and carrying capacity. Data are presented here using summary statistics (e.g. mean values per sample or site), frequency histograms and multivariate analyses to illustrate background data used as model input and data for prey species consumed by other waders. Note that the results of Ash Free Dry Mass (AFDM) measurements are not presented in the current report since detailed analyses of these were undertaken for the Pied Oystercatcher carrying capacity model and are described by Atkinson and Stillman (2008).

34 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Multivariate analyses were conducted including cluster analysis and multi-dimensional scaling (MDS) in order to produce graphical depictions of prey resource similarities between survey areas. For these analyses, the data matrix showing total abundance of species at each location was double root-transformed and then converted to a symmetric matrix of biotic similarity between pairs of locations using the Bray-Curtis similarity index. These procedures follow the recommendations of Faith et al. (1987) and Clarke (1993) for data matrices with numerous zero records (i.e. zero records for particular taxa). The usefulness of the two dimensional MDS display of relationships between sites is indicated by the stress statistic, which if <0.1 indicates that the depiction of relationships is good, and if >0.2 that the depiction is poor (Clarke 1993). Following application of MDS analysis, SIMPER analyses were conducted to ascertain which species had contributed most to patterns of similarity observed in the MDS plot.

4 RESULTS

The invertebrate sampling program was primarily designed to collect data required for the Pied Oystercatcher carrying capacity model, but also provides data on prey species for other important waders. The results of modelling the invertebrate data are not presented here, as they are described in conjunction with other model outputs by Atkinson and Stillman (2008). The current report instead provides the results of descriptive analyses that illustrate trends in densities and sizes of prey species that are relevant to Pied Oystercatchers and other waders. Because the ‘patches’ identified for the Pied Oystercatcher model were based primarily on feasibility of survey areas for bird counts and bird foraging observations, rather than habitat differences likely to influence densities of prey species, they are not used as a basis for descriptive analyses presented below. Instead, results are presented at a bay-wide level, with the exception of a more detailed spatial analysis conducted for three survey zones at Lauderdale.

4.1 INPUT DATA FOR THE PIED OYSTERCATCHER CARRYING CAPACITY MODEL

Data for benthic infauna and epibenthic prey species of the Pied Oystercatcher were processed as described in Section 3.5.3.1 and submitted as input for the Pied Oystercatcher carrying capacity model. These data were used to estimate the total prey resource in each patch, and hence estimate the carrying capacity of surveyed patches in conjunction with data on bird numbers, bird foraging rates, sandflat exposure and other model input data (refer to Atkinson and Stillman 2008).

4.2 INTERTIDAL BENTHIC INFAUNA

4.2.1 Comparisons between bays

The raw dataset for the intertidal benthic infauna samples is included as Appendix 11 in the estuarine and marine ecology technical report prepared for the IIS (Aquenal 2008b), including wader prey and all other invertebrate species recorded. This very large raw dataset is not repeated in the current report.

In order to focus on main prey and other species observed as wader dietary items, only those infauna species recorded in foraging observations by Harrison (2008) were analysed in the benthic infauna dataset. In the case of polychaetes, which could not be identified to species level during the foraging field surveys, data were only analysed for the three main prey species identified in Section 3.2, and these species were assumed to comprise prey for both Pied Oystercatchers and other wader species. An exception to the above approach was in the analysis of data for the measured ≥ 10 mm animals. In this case, additional potential prey species identified in samples were pooled into ‘Bivalve - Other’ and ‘Polychaete – Other’ groups and included in the analyses since there was a high likelihood that these animals contributed to the prey resource.

35 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Note that the benthic bivalve Fulvia tenuicostata was recorded as a prey item for the Bar-tailed Godwit at Lauderdale; however this bivalve species was not present in the intertidal invertebrate samples and therefore could not be included in data analysis. It was recorded in subtidal benthic infauna samples collected in Ralphs Bay as part of the estuarine and marine ecology survey (Aquenal 2008b), suggesting that it occurs primarily in subtidal habitats adjacent to the intertidal Lauderdale sandflat. Given the long beak of the Bar-tailed Godwit, it is possible that this species forages in habitats along the littoral/sublittoral fringe to access prey such as Fulvia tenuicostata that are not accessible to bird species with shorter beaks.

Certain other prey species reported by Harrison (2008), such as sea squirts (ascidians), beetles, flies, barnacles and fish were not targeted by the invertebrate sampling program and are not included in analyses here. Amphipods, isopods and shrimps were also excluded from analysis, since it was not feasible to identify these to species level in the field during the foraging ecology surveys and hence they could not be aligned to particular species in the invertebrate samples. For example, approximately 40 species of amphipods were recorded in the invertebrate survey (Appendix 11, Aquenal 2008b), and the extent to which each of these provide prey for waders is not clear. Given that including all of these species in data analyses may complicate interpretation of results for main prey species, they were excluded. Epibenthic mussels and oysters are addressed in Section 4.3 below.

A total of thirteen benthic infauna prey species were included in the data analyses that included individuals of all sizes. The average abundance per core sample of these species in each bay for the three seasons surveyed is indicated in Table 6 on the basis of samples from the invertebrate grid sites (note that additional sites sampled at Lauderdale to assess spatial variation in more detail were excluded from analyses here but are included in the analyses presented in Section 4.2.2). Since these data do not take into consideration the size of the individuals, they may include animals outside the size range observed in wader diets. They are therefore more indicative of total ‘potential’ prey resources through the year rather than total available resources at the particular time of each survey.

The average number of individuals across all prey species per core ranged from 3.7 to 15.2 in spring, 2.6 to 26.9 in summer and 9.11 to 21.6 in winter (Table 6). Orielton Lagoon consistently recorded the lowest density of prey species, while highest densities were recorded at Five Mile Beach in spring, and Mortimer Bay/Lauderdale in summer and winter. The winter data are considered most indicative for Orielton Lagoon, since the survey area was expanded at that time after wader foraging observations indicated that previous mapping of the low water mark was inaccurate. Across all three seasons, Lauderdale recorded the highest average density of prey species individuals (18.8), closely followed by Mortimer Bay (18.1).

Pooled data for taxonomic groups of prey species (Table 7) reveal that highest densities of bivalve and crab prey species were recorded at Five Mile Beach in all seasons. Densities of polychaetes were relatively even across bays in spring, whilst in summer and winter they were highest at Mortimer Bay followed by South Arm. The gastropod prey species Salinator fragilis was consistently most abundant at Lauderdale. Prey species at Barilla Bay and Five Mile Beach were dominated numerically by bivalves, while polychaetes dominated at Mortimer Bay, Pipeclay Lagoon and South Arm. At Lauderdale, densities of polychaete and bivalve prey species were similar in spring, while polychaetes dominated in summer and winter. At Orielton Lagoon, the dominant group also varied seasonally, although sampling from a more extensive network of sites in winter suggested the numerical dominance of bivalves. Densities of crab prey species were consistently low in samples from all bays, but were highest at Five Mile Beach and Pipeclay Lagoon, with the exception of reduced numbers at the latter location in winter.

When the same dataset was pooled across seasons, it was apparent that densities of bivalves were highest overall at Five Mile Beach, followed by Barilla Bay and then Lauderdale (Table 8). At Five Mile Beach the high density of bivalves was primarily attributable to elevated counts of Wallucina assimilis, a species that was only present in low numbers in the wader prey data compiled from foraging observations by Harrison (2008). In contrast, the dominant

36 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 6 Mean abundance per core sample of wader prey species in each bay including all individuals collected in core samples (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon).

Spring 2006 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 4.66 1.64 2.56 0.00 0.38 0.84 0.11 Katelysia scalarina Bivalvia (Mollusca) 0.07 0.46 0.99 0.85 0.00 0.25 0.32 Tellina deltoidalis Bivalvia (Mollusca) 0.09 0.00 0.14 0.00 0.12 0.02 0.14 Eumarcia fumigata Bivalvia (Mollusca) 0.05 0.00 0.03 0.05 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.02 0.00 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.45 7.46 0.05 0.05 0.00 1.59 0.00 Soletellina biradiata Bivalvia (Mollusca) 0.02 0.00 0.01 0.00 0.00 0.02 0.00 Nephtys australiensis Polychaeta (Annelida) 1.07 0.14 1.40 1.35 2.92 1.52 2.30 Leitoscoloplos normalis Polychaeta (Annelida) 2.25 3.14 1.85 1.75 0.04 1.44 0.32 Olganereis edmonsi Polychaeta (Annelida) 0.05 0.04 0.04 0.00 0.00 0.31 0.18 Paragrapsus gaimardii Decapoda (Crustacea) 0.00 0.04 0.05 0.05 0.00 0.02 0.00 Mictyris platycheles Decapoda (Crustacea) 0.00 0.36 0.00 0.00 0.00 0.34 0.00 Salinator fragilis Gastropoda (Mollusca) 1.02 1.89 3.01 1.60 0.23 0.61 1.43 Total 9.75 15.18 10.13 5.70 3.69 6.95 4.80 Summer 2007 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 6.89 1.43 3.08 0.00 0.12 0.66 0.07 Katelysia scalarina Bivalvia (Mollusca) 0.05 0.14 1.29 0.80 0.00 0.09 0.43 Tellina deltoidalis Bivalvia (Mollusca) 0.23 0.00 0.08 0.00 0.00 0.00 0.02 Eumarcia fumigata Bivalvia (Mollusca) 0.07 0.00 0.44 0.00 0.00 0.89 0.05 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.27 7.64 0.20 0.00 0.00 2.41 0.00 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.00 0.09 0.00 0.00 0.00 0.00 Nephtys australiensis Polychaeta (Annelida) 1.16 0.11 3.90 6.40 2.27 1.83 6.20 Leitoscoloplos normalis Polychaeta (Annelida) 0.25 3.18 1.04 0.95 0.00 0.84 0.61 Olganereis edmonsi Polychaeta (Annelida) 0.70 1.50 5.91 12.90 0.08 9.34 8.98 Paragrapsus gaimardii Decapoda (Crustacea) 0.02 0.00 0.09 0.00 0.00 0.03 0.05 Mictyris platycheles Decapoda (Crustacea) 0.00 0.32 0.03 0.00 0.00 0.13 0.05 Salinator fragilis Gastropoda (Mollusca) 0.64 2.43 9.85 5.85 0.12 3.08 2.77 Total 10.27 16.75 25.98 26.90 2.58 19.30 19.23 Winter 2007 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 5.72 2.71 3.68 0.28 5.39 0.70 0.45 Katelysia scalarina Bivalvia (Mollusca) 0.26 1.50 2.29 1.30 0.03 0.41 0.75 Tellina deltoidalis Bivalvia (Mollusca) 0.06 0.00 0.14 0.03 0.44 0.00 0.07 Eumarcia fumigata Bivalvia (Mollusca) 0.04 0.00 0.03 0.00 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.19 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.26 5.79 0.15 0.05 0.00 2.31 0.05 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.04 0.07 0.05 0.00 0.00 0.02 Nephtys australiensis Polychaeta (Annelida) 1.44 0.29 4.81 7.35 2.30 2.28 8.30 Leitoscoloplos normalis Polychaeta (Annelida) 0.76 1.29 0.71 0.55 0.03 0.67 0.36 Olganereis edmonsi Polychaeta (Annelida) 0.44 0.39 3.59 9.53 0.72 8.52 7.48 Paragrapsus gaimardii Decapoda (Crustacea) 0.02 0.07 0.07 0.00 0.00 0.02 0.00 Mictyris platycheles Decapoda (Crustacea) 0.00 0.29 0.01 0.00 0.00 0.02 0.02 Salinator fragilis Gastropoda (Mollusca) 0.70 2.18 4.69 2.48 0.02 2.22 2.14 Total 9.70 14.54 20.25 21.60 9.11 17.14 19.64 Mean total per season 9.91 15.49 18.78 18.07 5.13 14.46 14.55

37 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 7 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each bay, including all individuals collected (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon).

Season Taxonomic Group B F L M O P S Spring 2006 Total bivalves 5.36 9.57 3.78 0.95 0.50 2.72 0.57 Total polychaetes 3.36 3.32 3.29 3.10 2.96 3.27 2.80 Total crabs 0.00 0.39 0.05 0.05 0.00 0.36 0.00 Total gastropods 1.02 1.89 3.01 1.60 0.23 0.61 1.43

Summer 2007 Total bivalves 7.50 9.21 5.16 0.80 0.12 4.05 0.57 Total polychaetes 2.11 4.79 10.85 20.25 2.35 12.02 15.80 Total crabs 0.02 0.32 0.11 0.00 0.00 0.16 0.09 Total gastropods 0.64 2.43 9.85 5.85 0.12 3.08 2.77

Winter 2007 Total bivalves 6.34 10.04 6.36 1.70 6.05 3.42 1.34 Total polychaetes 2.64 1.96 9.12 17.43 3.05 11.47 16.14 Total crabs 0.02 0.36 0.08 0.00 0.00 0.03 0.02 Total gastropods 0.70 2.18 4.69 2.48 0.02 2.22 2.14

Table 8 Pooled mean abundances per core sample across seasons for wader prey species in each bay, including all individuals collected (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon).

Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 17.27 5.79 9.32 0.28 5.89 2.20 0.64 Katelysia scalarina Bivalvia (Mollusca) 0.37 2.11 4.57 2.95 0.03 0.75 1.50 Tellina deltoidalis Bivalvia (Mollusca) 0.38 0.00 0.35 0.03 0.55 0.02 0.23 Eumarcia fumigata Bivalvia (Mollusca) 0.15 0.00 0.49 0.05 0.00 0.89 0.05 Laternula tasmanica Bivalvia (Mollusca) 0.02 0.00 0.00 0.00 0.19 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.99 20.89 0.40 0.10 0.00 6.31 0.05 Soletellina biradiata Bivalvia (Mollusca) 0.02 0.04 0.17 0.05 0.00 0.02 0.02 Total bivalves 19.20 28.82 15.30 3.45 6.66 10.19 2.48 Total A. cycladea and K. scalarina 17.64 7.89 13.88 3.23 5.92 2.95 2.14

Nephtys australiensis Polychaete (Annelida) 3.67 0.54 10.11 15.10 7.49 5.63 16.80 Leitoscoloplos normalis Polychaete (Annelida) 3.26 7.61 3.60 3.25 0.07 2.95 1.30 Olganereis edmonsi Polychaete (Annelida) 1.19 1.93 9.54 22.43 0.80 18.17 16.64 Total polychaetes 8.12 10.07 23.25 40.78 8.35 26.75 34.73

Paragrapsus gaimardii Decapoda (Crustacea) 0.04 0.11 0.21 0.05 0.00 0.06 0.05 Mictyris platycheles Decapoda (Crustacea) 0.00 0.96 0.03 0.00 0.00 0.48 0.07 Total crabs 0.04 1.07 0.24 0.05 0.00 0.55 0.11

Salinator fragilis Gastropoda (Mollusca) 2.36 6.50 17.55 9.93 0.36 5.91 6.34 Total gastropods 2.36 6.50 17.55 9.93 0.36 5.91 6.34

Species contributing Total A. cycladea and ~90% of Pied K. scalarina and Oystercatcher prey polychaetes 25.76 17.96 37.14 44.00 14.28 29.70 36.86

38 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay species at Barilla Bay was Anapella cycladea, while at Lauderdale both A. cycladea and Katelysia scalarina were common. Given that A. cycladea and K. scalarina are the two bivalve species consumed most frequently by the Pied Oystercatcher, the total pooled bivalve data are likely to overestimate the bivalve foraging resource at Five Mile Beach.

When mean densities were pooled just for A. cycladea and K. scalarina, the highest total density was recorded at Barilla Bay, followed by Lauderdale and then Five Mile Beach. Anapella cycladea was most abundant at Barilla Bay, while K. scalarina was most abundant at Lauderdale, followed by Mortimer Bay. Lauderdale was relatively unique in having high densities of both A. cycladea and K. scalarina. Other waders feed less frequently on A. cycladea and K. scalarina than the Pied Oystercatcher, although these two species still contributed a larger percentage of prey items than other bivalves, with the exception of Soletellina biradiata (Table 2). Wallucina assimilis was not observed as a prey item for other waders, although it is possible that low numbers are taken.

On the basis of the pooled seasonal data, the highest overall density of polychaetes was at Mortimer Bay due to the proliferation of Olganereis edmonsi during summer and winter months (Table 6). Following Mortimer Bay, polychaete density was highest at South Arm, Pipeclay Lagoon and Lauderdale, with O. edmonsi again contributing a large portion of numbers observed in summer and winter months. At Lauderdale and South Arm, overall densities of O. edmonsi and Nephtys australiensis were comparable, with Leitoscoloplos normalis less common. Olganereis edmonsi dominated at Mortimer Bay and Pipeclay Lagoon, while Nephtys australiensis was the most common polychaete at Orielton Lagoon and L. normalis at Five Mile Beach (Table 7). Crab prey species were most abundant overall at Five Mile Beach followed by Pipeclay Lagoon, with the soldier crab Mictyris platycheles the dominant species at both locations. The gastropod Salinator fragilis was most abundant at Lauderdale, followed by Mortimer Bay. This species was originally indicated to comprise prey for the Pied Oystercatcher at Lauderdale, South Arm and south Pipeclay Lagoon (see Section 3.2.1) and for an additional wader species at north Pipeclay Lagoon (Sooty Oystercatcher), however the final foraging ecology dataset also indicates it as a minor prey item at Mortimer Bay (Harrison 2008).

For the Pied Oystercatcher, the bivalves Anapella cycladea and Katelysia scalarina together with the polychaetes comprised ~90% of the total count of observed Pied Oystercatcher dietary items (Table 1). It is therefore useful to assess the total density of these species combined, with results included at the base of Table 8. The combined density of these species was greatest at Mortimer Bay, followed by Lauderdale and South Arm. These prey data may therefore provide a key to the importance of Ralphs Bay for this wader species (see Aquenal 2008a). Across all seasons and within this group of prey species only, the two bivalves accounted for 37% of counted prey species at Lauderdale and just 6-7% at Mortimer Bay and South Arm; while polychaetes contributed 63% at Lauderdale and 93-94% at the other two bays.

Note that the diets of the Pied Oystercatcher and other wader species overlapped in terms of observed prey species present in the benthic infauna samples. While certain bivalve species were observed as prey for Pied Oystercatchers but not for other waders, these bivalves were recorded in low numbers during foraging observations for the former species. Given that the Pied Oystercatcher was more intensively surveyed, it is feasible that other waders also consumed these bivalve species. Therefore, multivariate analyses described below incorporated the entire range of prey listed in Table 6 above and are interpreted in relation to information on dietary composition provided by Harrison (2008) for Pied Oystercatchers and other wader species.

The results of multi-dimensional scaling (MDS) analysis using mean seasonal data for each bay, incorporating all prey species individuals (i.e. all sizes) in core samples, are presented in the MDS plot in Figure 16. The stress statistic of 0.13 indicates reliable depictions of similarities amongst bays and seasons. Orielton Lagoon was an outlier in all seasons, with SIMPER analyses suggesting this to primarily be the result of very low densities of the polychaete Olganereis edmonsi in the lagoon. This area also recorded low densities of the bivalve Katelysia scalarina, polychaete Leitoscoloplos normalis and gastropod Salinator fragilis, while densities of the bivalve

39 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Anapella cycladea and polychaete Nephtys australiensis were comparable to those in other bays (Table 6). Whilst relatively uncommon in all bays, the bivalves Tellina deltoidalis and Laternula tasmanica were most common at Orielton Lagoon, consistent with these species being recorded more frequently as prey items in the lagoon than in most other areas (Harrison 2008). Data in Table 6 indicate that Orielton Lagoon is depauperate overall in prey species; however the moderate densities of species such as N. australiensis and A. cycladea reflect a suitable food source for Pied Oystercatchers and other waders.

O-W Stress: 0.13 B F B-Sp

F-Su P-Sp B-Su L M B-W F-Sp O-Sp F-W L-Sp O P L-Su L-W

P-W P-Su S-Sp S-W S M-W O-Su S-Su

M-Sp

M-Su

Figure 16 MDS plot of mean densities of prey species for bays in each season surveyed (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007. Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm).

The MDS plot also indicates that seasonal differences in prey assemblages are small compared with inter-bay differences, as shown by the general tight grouping of data points representing the three seasons at each bay. This was most obvious at Lauderdale, Barilla Bay and Five Mile Beach, and also at Orielton Lagoon, where despite the widely dispersed data points, all seasons formed a grouping on the right side of the plot (Figure 16). In the broad grouping of sites on the left side, Mortimer Bay and South Arm overlapped to some extent and were located towards the base of the plot due to higher densities of Olganereis edmonsi and Nephtys australiensis and lower densities of Anapella cycladea than the bays in the top half of the plot. Within the remaining bays, Five Mile Beach was differentiated due to a higher density of the bivalve Wallucina assimilis and lower density of Olganereis edmonsi. Prey species assemblages at Lauderdale were most similar to those at Pipeclay Lagoon and Barilla Bay.

The data were further analysed using tidal data collected during a detailed assessment of ‘patch exposure’ (refer to Atkinson and Stillman 2008) to categorise sites according to tide height. As described in Section 3.3.1, each site was allocated to one of four tide height categories, with 1 representing the area highest on the shore (i.e. inundated for the shortest length of time) and 4 representing the area lowest on the shore (i.e. inundated for the greatest length of time). The results are presented by season in Figure 17 with stress statistic values of 0.19-0.21, reflecting borderline values in terms of the plots providing reliable depictions of similarities amongst sites. While there was a high level of overlap in prey assemblages between tide levels, the majority of sites in the highest shore group (tide category 1; red symbols in Figure 17) formed a grouping in each seasonal plot. SIMPER analysis indicated that this group had higher densities of the bivalve Anapella cycladea and gastropod Salinator fragilis than the lower shore level groups. The sites lowest on the shore (tide category 4; dark blue symbols in Figure 17) tended to be limited to one half of the

40 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Stress: 0.2 Spring 2006

Stress: 0.21 B1 B2 B3 B4 F1 Summer 2007

F2 F3 F4 L1 L2

L3 L4 M3 M4 O2

O3 O4 P1 P2 P3

P4 S1 S2 S3 S4

Stress: 0.19 Winter 2007

Figure 17 MDS plots of mean densities of prey species for sites in each bay and in each season surveyed in accordance with tide height category (Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm; Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore).

41 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay plot and were characterised by a low density of A. cycladea and S. fragilis. This delineation is best exemplified by the large number of sites sampled at Lauderdale in winter, with low shore sites on the left side of the plot and high shore sites on the right. Patterns of spatial variation at Lauderdale are described in more detail in Section 4.2.2.

These results are particularly significant for Anapella cycladea, which was recorded as one of the main prey items for the Pied Oystercatcher (and for the Sooty Oystercatcher in Pipeclay Lagoon; Harrison 2008), since the concentration of this species high on the shore means that it will be available as a prey resource for the majority of the tidal cycle. While tide height was clearly important in determining the composition of prey assemblages, some groupings based on geographical separation of bays are also evident in Figure 17. For example, the Lauderdale sites (opaque circles) tended to form a group in the centre of the plot, suggesting that they are ‘intermediate’ with relation to prey assemblages in other bays.

Given that the data presented above incorporate all individuals recorded in core samples, including those that may be smaller than the sizes observed to be consumed by waders, some additional analyses were conducted using measured individuals. As described in Section 3.5.1, length measurements were recorded for all polychaetes and bivalves, as well as Salinator fragilis in areas where this species was identified as a Pied Oystercatcher prey item, with all animals ≥ 10 mm subsequently deemed to be ‘available’ as prey for waders. Table 9 provides average density data for individuals ≥ 10 mm, but is limited to species which were identified early in the foraging survey program as important for Pied Oystercatchers and hence were measured to provide size data input for the carrying capacity model for that species. Size measurement data are therefore not available for Paragrapsus gaimardii or Mictyris platycheles, but are available for the remaining species discussed above.

Note that in order to utilise the size data for the full range of possible available prey items, additional less common bivalves and polychaetes within the size range consumed were included in the data analyses presented below, allocated to the pooled categories of ‘Bivalve – Other’ or ‘Polychaete – Other’. A list of the less common species included in the analyses is indicated in Table 5. These species were not observed during the foraging surveys by Harrison (2008), however it was not feasible during those surveys to identify polychaetes to species level while the less common bivalves may have been difficult to detect due to low uptake rates. The additional less common species were not included in the above analyses based on individuals of all sizes, since there was the potential to include large numbers of animals that do not contribute to the prey resource; however these species in the ≥ 10 mm datasets occurred in low numbers and are more likely to provide suitable prey.

To facilitate comparisons between the dataset incorporating all individuals in core samples [Table 6 to Table 8; which was limited to species observed to be wader prey items by Harrison (2008)] and the dataset limited to individuals ≥ 10 mm, total prey densities in Table 9 have been calculated both with and without the extra additional less common bivalves and polychaetes. Note also that the totals for each bay excluded the gastropod Salinator fragilis since size data for this species was not collected in all bays or all parts of bays (e.g. at Pipeclay Lagoon, it was only measured in samples from the southern survey zone - patch 3 in Figure 15g).

Based on data for ≥ 10 mm individuals, the average number of individuals across all prey species per core including all bivalves and polychaetes ranged from 1.7 to 5.1 in spring, 0.4 to 7.4 in summer and 2.3 to 6.1 in winter (Table 9). As with data for individuals of all sizes, Orielton Lagoon consistently recorded the lowest density of individuals of prey species. Highest densities of prey were recorded at Lauderdale and South Arm in summer and winter. Contrasting with results in Table 6 for all individuals, the peak in prey numbers at Five Mile Beach in spring was absent, supporting the earlier suggestion that many of the Wallucina assimilis recorded there do not contribute to the available prey resource. The exclusion of ‘Bivalves - Other’ or ‘Polychaetes - Other’ had little affect on overall density totals or patterns of variation amongst bays. The mean total density of ≥ 10 mm individuals per season was highest at South Arm, closely followed by Lauderdale. This differed from the data for all individuals which indicated the highest density of prey species at Lauderdale followed by Mortimer Bay, and suggests that a higher

42 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay portion of prey were smaller than the size consumed by birds at these two locations compared with South Arm. All sets of results confirm that the Ralphs Bay locations provide the highest density of prey species suitable for the Pied Oystercatcher. Since many of the prey species taken by other waders were not measured, they are not included in the ≥ 10 mm dataset, but the polychaetes were a food source for many of the wader species (Harrison 2008) and hence the results reported below for that prey type are applicable to these waders.

Pooled data for taxonomic groups of prey species (Table 10) reveal that highest densities of bivalves ≥ 10 mm were recorded at Lauderdale, closely followed by Barilla Bay in summer and winter. This again indicates that while Five Mile Beach recorded the highest densities across all seasons on the basis of individuals of all sizes, a large portion of these were smaller than the size consumed by waders. As reported for data including all individuals, densities of polychaetes were relatively even across bays in spring. In summer and winter they were highest at South Arm followed by Mortimer Bay, as opposed to the result recorded using data for all individuals. This indicates that while both of these bays have high densities of polychaete prey species, the most abundant polychaete prey that were suitable for wader consumption during the survey period were at South Arm.

The gastropod Salinator fragilis occurred at highest densities at Lauderdale in summer and in spring, and at South Arm in winter. Prey species ≥ 10 mm were dominated numerically in all seasons by polychaetes at Mortimer Bay, South Arm, Pipeclay Lagoon and Orielton Lagoon, and by bivalves at Lauderdale and Five Mile Beach. Densities of polychaetes and bivalves were however fairly similar at Lauderdale during winter and, in particular, spring. At Barilla Bay, densities of polychaetes dominated during spring, however subsequent domination of bivalves in summer and winter indicates a large recruitment of bivalves into the ≥ 10 mm size range following spring. In bays where S. fragilis was measured, this gastropod consistently contributed a lower count than the bivalve and polychaete total counts.

These results are consistent to a large extent with the results for data including individuals of all sizes; however the higher density of bivalves than polychaetes at Lauderdale during summer and winter is inconsistent with the data reported in Table 7. This suggests that a large portion of polychaetes recorded at Lauderdale during the survey were smaller than the size generally consumed by birds.

When the ≥ 10 mm density dataset was pooled across seasons, numbers of bivalves were highest overall at Lauderdale, followed by Barilla Bay (Table 11), as opposed to the highest total recorded at Five Mile Beach for individuals of all sizes. Wallucina assimilis, which was the dominant bivalve at Five Mile Beach using all individuals, only contributed a very small percentage of the ≥ 10 mm bivalves in this bay. Anapella cycladea was the dominant bivalve for ≥ 10 mm individuals in all bays except Mortimer Bay and South Arm, where Katelysia scalarina was more common. In these two bays, the low density of A. cycladea in samples may reflect steeper upper shores and hence reduced habitat for this predominantly high-shore species, since analysis of tide height data (Figure 17) indicated that the majority of these two bays were located in the two lowest shore tide categories. The density of K. scalarina was still highest at Lauderdale, as was the density of A. cycladea, although the latter was nearly as abundant at Barilla Bay. Conversely, on the basis of all individuals, Barilla Bay recorded by far the highest density of A. cycladea (Table 8) indicating that many animals collected there were too small to be available as prey to waders.

On the basis of the pooled seasonal data for ≥ 10 mm individuals, the highest overall density of polychaetes was recorded at South Arm followed by Mortimer Bay (Table 11). This is similar to the result using all individuals, except that Mortimer Bay recorded the highest densities due to a larger number of < 10 mm individuals than at South Arm. It is notable also that while Olganereis edmonsi was the dominant species in these two bays on the basis of all individuals, Nephtys australiensis dominated counts of ≥ 10 mm animals. Given that O. edmonsi was not abundant in the spring survey, these data indicate that a major recruitment event occurred for this species subsequent

43 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 9 Mean abundance per core sample of wader prey species individuals ≥ 10 mm length (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon).

Spring 2006 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 0.82 1.61 2.31 0.00 0.35 0.84 0.11 Katelysia scalarina Bivalvia (Mollusca) 0.07 0.39 0.20 0.35 0.00 0.08 0.16 Tellina deltoidalis Bivalvia (Mollusca) 0.07 0.00 0.08 0.00 0.04 0.00 0.09 Eumarcia fumigata Bivalvia (Mollusca) 0.02 0.00 0.01 0.05 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.04 0.03 0.00 0.00 0.03 0.00 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.04 0.00 0.00 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.00 0.00 0.05 0.00 0.00 0.00 0.02 Nephtys australiensis Polychaeta (Annelida) 0.73 0.04 1.20 1.30 0.81 0.77 1.66 Leitoscoloplos normalis Polychaeta (Annelida) 1.11 0.82 0.99 1.55 0.04 0.41 0.18 Olganereis edmonsi Polychaeta (Annelida) 0.02 0.04 0.01 0.05 0.00 0.19 0.14 Polychaetes – Other * Polychaeta (Annelida) 0.36 0.57 0.21 0.35 0.46 0.89 0.39 Salinator fragilis # Gastropoda (Mollusca) N/A N/A 0.21 N/A N/A 0.16 0.20 Total (excl. #) 3.20 3.54 5.09 3.65 1.69 3.20 2.75 Total (excl. # and *) 2.84 2.96 4.83 3.30 1.23 2.31 2.34 Summer 2007 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 3.30 1.43 2.44 0.00 0.08 0.58 0.07 Katelysia scalarina Bivalvia (Mollusca) 0.02 0.14 1.09 0.70 0.00 0.02 0.27 Tellina deltoidalis Bivalvia (Mollusca) 0.09 0.00 0.08 0.00 0.00 0.00 0.02 Eumarcia fumigata Bivalvia (Mollusca) 0.09 0.00 0.03 0.00 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.02 0.04 0.00 0.00 0.00 0.02 0.00 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.00 0.03 0.00 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.02 0.00 0.03 0.00 0.00 0.00 0.00 Nephtys australiensis Polychaeta (Annelida) 0.11 0.00 0.61 1.10 0.19 0.23 2.27 Leitoscoloplos normalis Polychaeta (Annelida) 0.00 0.71 0.03 0.10 0.00 0.25 0.16 Olganereis edmonsi Polychaeta (Annelida) 0.02 0.04 0.19 1.15 0.00 0.44 4.16 Polychaetes – Other * Polychaeta (Annelida) 0.16 0.57 0.04 0.15 0.12 0.19 0.41 Salinator fragilis # Gastropoda (Mollusca) N/A N/A 0.45 N/A N/A 0.17 0.18 Total (excl. #) 3.84 2.93 4.54 3.20 0.38 1.72 7.36 Total (excl. # and *) 3.66 2.36 4.48 3.05 0.27 1.53 6.95 Winter 2007 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 2.90 2.25 2.33 0.00 0.45 0.55 0.66 Katelysia scalarina Bivalvia (Mollusca) 0.08 0.18 0.82 0.60 0.00 0.06 0.73 Tellina deltoidalis Bivalvia (Mollusca) 0.02 0.00 0.11 0.03 0.28 0.00 0.07 Eumarcia fumigata Bivalvia (Mollusca) 0.04 0.00 0.00 0.00 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.06 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.02 0.00 0.00 0.00 0.00 0.03 0.07 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.00 0.02 0.07 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.00 0.00 0.04 0.00 0.00 0.00 0.02 Nephtys australiensis Polychaeta (Annelida) 0.82 0.00 1.69 2.80 0.94 0.84 2.75 Leitoscoloplos normalis Polychaeta (Annelida) 0.04 0.00 0.10 0.10 0.00 0.05 0.02 Olganereis edmonsi Polychaeta (Annelida) 0.04 0.11 0.60 1.37 0.04 1.14 1.48 Polychaetes – Other * Polychaeta (Annelida) 0.60 0.50 0.13 0.93 0.55 0.39 0.30 Salinator fragilis # Gastropoda (Mollusca) N/A N/A 0.36 N/A N/A 0.25 0.45 Total (excl. #) 4.56 3.04 5.85 5.90 2.32 3.06 6.09 Total (excl. # and *) 3.96 2.54 5.68 4.97 1.77 2.67 5.77 Mean total per season (excl. #) 3.87 3.17 5.16 4.25 1.47 2.66 5.40 Mean total per season (excl. # and *) 3.49 2.62 4.99 3.77 1.09 2.17 5.02

44 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 10 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each bay, on the basis of individuals ≥ 10 mm (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon).

Season Taxonomic Group B F L M O P S Spring 2006 Total bivalves (all) 0.98 2.07 2.68 0.40 0.38 0.95 0.39 Total bivalves (excluding 'Bivalves - Other') 0.98 2.07 2.63 0.40 0.38 0.95 0.36 Total polychaetes (all) 2.23 1.46 2.41 3.25 1.31 2.25 2.36 Total polychaetes (excluding 'Polychaetes - Other') 1.86 0.89 2.20 2.90 0.85 1.36 1.98 Total gastropods N/A N/A 0.21 N/A N/A 0.16 0.20 Summer 2007 Taxonomic Group B F L M O P S Total bivalves (all) 3.55 1.61 3.68 0.70 0.08 0.61 0.36 Total bivalves (excluding 'Bivalves - Other') 3.52 1.61 3.65 0.70 0.08 0.61 0.36 Total polychaetes (all) 0.30 1.32 0.86 2.50 0.31 1.11 7.00 Total polychaetes (excluding 'Polychaetes - Other') 0.14 0.75 0.83 2.35 0.19 0.92 6.59 Total gastropods N/A N/A 0.45 N/A N/A 0.17 0.18 Winter 2007 Taxonomic Group B F L M O P S Total bivalves (all) 3.06 2.43 3.32 0.70 0.79 0.64 1.55 Total bivalves (excluding 'Bivalves - Other') 3.06 2.43 3.28 0.70 0.79 0.64 1.52 Total polychaetes (all) 1.50 0.61 2.53 5.20 1.53 2.42 4.55 Total polychaetes (excluding 'Polychaetes - Other') 0.90 0.11 2.40 4.27 0.98 2.03 4.25 Total gastropods N/A N/A 0.36 N/A N/A 0.25 0.45

Table 11 Pooled mean abundances per core sample across seasons for wader prey species in each bay on the basis of individuals ≥ 10 mm (Bays: L = Lauderdale, M = Mortimer Bay, S = South Arm, P = Pipeclay Lagoon, F = Five Mile Beach, B = Barilla Bay, O = Orielton Lagoon).

Spring 2006 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 7.01 5.29 7.08 0.00 0.87 1.97 0.84 Katelysia scalarina Bivalvia (Mollusca) 0.17 0.71 2.11 1.65 0.00 0.16 1.16 Tellina deltoidalis Bivalvia (Mollusca) 0.18 0.00 0.26 0.03 0.32 0.00 0.18 Eumarcia fumigata Bivalvia (Mollusca) 0.15 0.00 0.04 0.05 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.06 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.04 0.07 0.03 0.00 0.00 0.08 0.07 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.04 0.05 0.07 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.02 0.00 0.12 0.00 0.00 0.00 0.05 Total bivalves (all) 7.58 6.11 9.67 1.80 1.25 2.20 2.30 Total bivalves (excluding *) 7.56 6.11 9.56 1.80 1.25 2.20 2.25 Nephtys australiensis Polychaeta (Annelida) 1.66 0.04 3.51 5.20 1.94 1.84 6.68 Leitoscoloplos normalis Polychaeta (Annelida) 1.15 1.54 1.11 1.75 0.04 0.70 0.36 Olganereis edmonsi Polychaeta (Annelida) 0.09 0.18 0.80 2.57 0.04 1.77 5.77 Polychaetes – Other # Polychaeta (Annelida) 1.12 1.64 0.38 1.43 1.13 1.47 1.09 Total polychaetes (all) 4.02 3.39 5.80 10.95 3.15 5.78 13.91 Total polychaetes (excluding #) 2.90 1.75 5.42 9.52 2.02 4.31 12.82 Salinator fragilis Gastropoda (Mollusca) - Total N/A N/A 1.03 N/A N/A 0.58 0.84

Species contributing Total A. cycladea and K. ~90% of Pied scalarina and polychaetes 11.21 9.39 14.99 12.60 4.02 7.91 15.91 Oystercatcher prey Total A. cycladea and K. scalarina and polychaetes (excluding #) 10.08 7.75 14.61 11.17 2.89 6.44 14.82

45 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay to the spring survey but that a portion of animals recorded in summer and winter were still too small to provide wader food. This was particularly notable at Mortimer Bay, where the disparity between O. edmonsi counts in the ‘all individuals’ and ‘≥ 10 mm individuals’ datasets was greatest. In the ≥ 10 mm individuals, N. australiensis was the most abundant species in samples from all remaining bays, with the exception of Five Mile Beach, where Leitoscoloplos normalis was most abundant. These results for other bays are consistent with findings for the dataset including all individuals, except that O. edmonsi was the most abundant polychaete species in the Pipeclay Lagoon samples when all individuals were included. Apart from South Arm and Mortimer Bay, Lauderdale recorded a higher density of polychaetes than other bays, although Pipeclay Lagoon recorded a similar value when all uncommon as well as common polychaete species were included in calculations. Consistent with data for individuals of all sizes, pooled data across seasons indicated that the gastropod Salinator fragilis reached highest densities at Lauderdale (Table 11).

Pooled data for the prey items that comprise ~90% of the Pied Oystercatcher diet (i.e. bivalves Anapella cycladea and Katelysia scalarina and the polychaetes) recorded the highest density at South Arm, closely followed by Lauderdale, and then Mortimer Bay on the basis of the ≥ 10 mm individuals (Table 11). Data incorporating all individuals also indicated highest densities in these three bays, but Mortimer Bay had recorded the highest total count (Table 8). This difference is due primarily to the high density of Olganereis edmonsi at Mortimer Bay which included a large proportion of < 10 mm animals. Consistent with data incorporating all individuals, A. cycladea and K. scalarina contributed a much larger proportion of ≥ 10 mm prey species counts at Lauderdale (61%) compared with Mortimer Bay (13%) and South Arm (13%). The percentage contribution of these bivalves increased for all three bays on the basis of the ≥ 10 mm data; however the biggest increase (24%) was recorded at Lauderdale. This supports earlier comments regarding the high concentration of food suitable for the Pied Oystercatcher within Ralphs Bay. Polychaetes are also a major food source for other wader species, while the bivalves A. cycladea and K. scalarina are generally not, with the exception of the Sooty Oystercatcher (Harrison 2008). Data above indicate that available resources relating to the polychaete component of the diet for other wader species also occur in greater densities in Ralphs Bay than remaining parts of the study area. Following Ralphs Bay sites, Pipeclay Lagoon and then Barilla Bay recorded the highest densities of polychaetes within the size range generally consumed by waders.

Multi-dimensional scaling (MDS) analysis was also performed using the seasonal density data for individuals ≥ 10 mm, with the resulting plot presented in Figure 18. The stress statistic of 0.14 for the plot indicates reliable depictions of similarities amongst bays and seasons. Note that the data included in this analysis were limited to bivalve and polychaete species individually listed in Table 9, since the gastropod Salinator fragilis was not measured in samples from all bays. The MDS analysis plot presented below also excluded species in the ‘Bivalves – Other’ and ‘Polychaetes – Other’ categories, however the analysis re-run including these prey categories produced a very similar plot. The results of the analysis are also very similar to those for the dataset including all individuals, with Orielton Lagoon differentiated from all other bays, and Lauderdale forming an intermediate group in the centre of the plot. SIMPER analysis indicated again that the more depauperate Orielton Lagoon samples were unique due to a low density of a range of prey species; Table 9 reveals lower densities of the bivalves Anapella cycladea and Katelysia scalarina and polychaetes Olganereis edmonsi and Leitoscoloplos normalis than in most other bays.

Consistent with data for all individuals, the MDS plot indicates that seasonal differences in prey assemblages are small compared with inter-bay differences. The three seasonal datapoints for each bay generally formed a grouping that was separated from groupings for other bays (Figure 18). In the broad grouping of bays on the left side of the plot, Lauderdale, Pipeclay Lagoon, South Arm and Barilla Bay (except in summer) formed a distinct subgroup, while Mortimer Bay and Five Mile Beach were more dissimilar. SIMPER analysis indicated that Mortimer Bay samples were characterised by lower densities of Anapella cycladea than the Lauderdale/other subgroup; in fact no specimens of A. cycladea ≥ 10 mm were detected, although this species was documented as a food source for the Pied Oystercatcher in Mortimer Bay (Harrison 2008). Some of the samples from non-grid sites surveyed to help inform the foraging surveys and target A. cycladea (sites 11, 12, 25) (refer to Section 3.3.1) did contain a solitary A. cycladea individual ≥ 10 mm, however only the uniformly dispersed grid sites were included in the data analysis to

46 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay prevent bias caused by targeting specific areas. Five Mile Beach was distinct from the Lauderdale/other subgroup due to a low density of the polychaete Nephtys australiensis ≥ 10 mm, with this species only recorded (in low numbers) in spring (Table 9), and reduced densities of the polychaete Olganereis edmonsi. The bivalve Wallucina assimilis had a much smaller role in differentiating Five Mile Beach from other bays than in the analysis incorporating animals of all sizes collected, since the density of this species was much reduced when only ≥ 10 mm animals were considered.

M-W Stress: 0.14 B F M-Su S-Su O-Sp M-Sp S-Sp L M S-W L-W O-W P-W L-Su O P P-Sp P-Su B-Sp O-Su L-Sp B-W F-Sp S

F-Su B-Su

F-W

Figure 18 MDS plot of mean densities of prey species individuals ≥ 10 mm for bays in each season surveyed (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007. Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm).

Data for the ≥ 10 mm dataset were further analysed at the level of site, with sites categorised according to tide height as described earlier for the ‘all individuals’ dataset (Figure 19). While there was again a high level of overlap amongst sites sampled at different tidal heights, those from the highest tide level (red symbols) tended to concentrate in a portion of the plot and there was little overlap between these and sites located at the lowest tide height (dark blue symbols). SIMPER analysis revealed that this was due primarily to elevated densities of Anapella cycladea and Salinator fragilis higher on the shore, while the density of Nephtys australiensis increased on the lowest part of the shore. The wide scatter of the Lauderdale sites (opaque circles) in Figure 19 indicates that this location was highly representative of the prey assemblages found across the wider study area.

The dataset for ≥ 10 mm animals collected at grid survey sites was further assessed to document the size frequency distributions of animals in the size range consumed by birds. Size frequency histograms are presented in Figure 20 to Figure 26 for each of the bivalves Anapella cycladea and Katelysia scalarina, and the polychaetes Nephtys australiensis, Leitoscoloplos normalis and Olganereis edmonsi, and for all other bivalves pooled and all other polychaetes pooled. Note that, consistent with data prepared for the carrying capacity model (see Section 3.5.3.1), a size class indicated as 10-14 mm, for example, corresponds to all animals from 10 mm through to < 15 mm. There was little value in presenting separate graphs for other bivalve species listed in the tables above due to the very small samples sizes of individuals ≥ 10 mm.

The number of sample sites varied amongst the bays, as indicated in the size frequency histogram figures, and hence these histograms are presented in order to compare relative contributions of size classes rather than overall counts.

47 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Stress: 0.16 Spring 2006

Stress: 0.12 Summer 2007 B1 B2 B3 B4

F2 F3 F4 L1

L3 L2 L4 M3

M4 O2 O3 P1

P2 P3 P4 S2

S3 S4

Stress: 0.14 Winter 2007

Figure 19 MDS plots of mean densities of prey species for sites in each bay and in each season surveyed in accordance with tide height category and only including ≥ 10 mm individuals (Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm; Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore).

48 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 12 indicates mean size for each of the above species and pooled groups in each bay to further facilitate comparisons of available prey sizes during the survey period. Where no ≥ 10 mm individuals of a certain species or pooled group were recorded in samples from a bay, the entry in the table is ‘N/A’. The variable sample sizes associated with these means can be seen from the variation in counts for animals ≥ 10 mm indicated by the size frequency histograms. The more detailed analysis of data for Lauderdale (Section 4.2.2) also examines the relationship between size and tide height for each species to determine if animal size may be related to the tidal gradient. This analysis was limited to Lauderdale, since a larger number of sites at various tidal heights was examined at this location and hence it provides the best assessment of whether these two parameters may be related.

The size frequency histograms for the bivalve Anapella cycladea indicate the dominance of the 15-19 mm size category, particularly in the final winter survey, at Lauderdale, Five Mile Beach and Orielton Lagoon (Figure 20). In contrast, the dominance of the 10-14 mm size class at Barilla Bay suggests a more recent recruitment event at that location. On the basis of invertebrate grid samples, the mean size of this species was largest at South Arm, followed by Pipeclay Lagoon (Table 12).

Mean size of Katelysia scalarina was also greatest at South Arm, except in spring where a small number of animals at Mortimer Bay included some large individuals, and the population was dominated by the 30-34 and 35-39 mm size categories (Figure 21). This species exhibited relatively low levels of recent recruitment in most bays, with the exception of Lauderdale and Mortimer Bay where the populations were dominated by animals in the range of 10-24 mm. The spike in animal numbers in the 20-24 mm size class at Lauderdale during the final winter survey reflects the growth of animals which contributed to smaller size classes in the previous seasons. While Lauderdale K. scalarina had a lower mean size than most other bays (Table 12), its high recruitment levels combined with higher mean density (Table 8, Table 11) suggest it to be an important food resource at this location.

Size frequency data for other pooled bivalve species are presented in Figure 22, although it is difficult to interpret recruitment patterns due to these plots being based on a range of less common species which may exhibit variable recruitment and growth patterns within locations. The largest individuals typically consisted of Tellina deltoidalis, while the largest mean size of these pooled species was recorded at South Arm followed by Lauderdale in spring, Lauderdale in summer (with the exception of Mortimer Bay, based on a very small sample size in non-grid samples) and Orielton Lagoon in winter (Table 12).

Most recent recruitment of the polychaete Nephtys australiensis into the ‘available’ size range was recorded at the three Ralphs Bay locations and at Pipeclay Lagoon, as indicated by spikes in numbers for the smallest available size classes (Figure 23). Particularly high numbers in winter at Lauderdale and Mortimer Bay are at least partially an artefact of the larger numbers of grid sample sites at those locations during the winter survey. The size data suggest that this species contributes little to the available prey resource at Five Mile Beach, consistent with its overall low density at this location (Table 8, Table 11). The mean size of N. australiensis showed considerable seasonal variation, and there was no clear trend for it to be larger in particular bays. The high mean size estimate at Five Mile Beach in spring (Table 12) was based on one animal only and therefore does not provide comparable data to those based on larger sample sizes in other bays.

The polychaete Leitoscoloplos normalis also exhibited a high level of seasonal variation in mean size at each particular bay, such that there was no clear relationship between size and geographical location. This species included occasional large worms in the size range of 55 to 69 mm at several locations. There was evidence of recent recruitment for this species at Barilla Bay, Lauderdale, Five Mile Beach and Pipeclay Lagoon during the spring survey; however densities of ≥ 10 mm animals were much reduced during subsequent surveys (Figure 24).

49 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

140 140

120 120

100 Barilla Bay 100 Five Mile Beach 80 80

Frequency n = 44 (s)

Frequency n = 28 60 60 n = 50 (w) 40 40 20 20

0 0 10-14 15-19 20-24 25-29 30-34 35-39 10-14 15-19 20-24 25-29 30-34 35-39

Size class (mm) Size class (mm)

140 140

120 Lauderdale 120

100 100 Orielton Lagoon

80 n = 80 (s) 80 n = 26 (s)

60 n = 121 (w) Frequency 60 n = 47 (w)

Frequency 40 40

20 20

0 0 10-14 15-19 20-24 25-29 30-34 35-39 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm) Size class (mm)

140 140 120 120

100 100 Pipeclay Lagoon South Arm 80 80

60 60 n = 64 Frequency n = 44

Frequency 40 40

20 20

0 0 10-14 15-19 20-24 25-29 30-34 35-39 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm) Size class (mm)

120 Spring 2006 100

40 Summer 2007 20

0 10-14Winter15- 20-24 25- 30-34 35-2007 19 29 39

Figure 20 Size frequency histograms for the bivalve Anapella cycladea in each bay, with data provided for the three seasons surveyed. Note that no A. cycladea ≥ 10 mm were recorded from Mortimer Bay grid samples. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable.

50 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

50 50

40 40

n = 44 (s) n = 28 30 Barilla Bay n = 50 (w) 30 Five Mile Beach

Frequency Frequency 20 20

10 10

0 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 10-14 15-19 20-24 25-29 30-34 35-39 40-44 Size class (mm) Size class (mm)

50 50

40 40 Mortimer Bay Lauderdale 30 n = 80 (s) 30 n = 20 (s) n = 121 (w) n = 30 (w) 20 Frequency 20 Frequency 10 10

0 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 10-14 15-19 20-24 25-29 30-34 35-39 40-44 Size class (mm) Size class (mm)

50 50

40 40

South Arm 30 Pipeclay Lagoon 30 n = 64 n = 44 20 20 Frequency Frequency 10 10

0 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 10-14 15-19 20-24 25-29 30-34 35-39 40-44 Size class (mm) Size class (mm)

120 Spring 2006 100

40 Summer 2007 20 0 10-14Winter15- 20-24 25- 30-34 35-2007 19 29 39

Figure 21 Size frequency histograms for the bivalve Katelysia scalarina in each bay, with data provided for the three seasons surveyed. Note that no K. scalarina ≥ 10 mm were recorded from Orielton Lagoon samples. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable.

51 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

10 10 10

8 8 8 Barilla Bay

Five Mile Beach

6 Barilla Bay 6 6 n = 44 (s) n = 28 4 4 4 n = 50 (w) Frequency Frequency Frequency 2 2 2

0 0 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 45-49 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 10-14 15-19 20-24 25-29 30-34 35-39 40-44 Size class (mm) Size class (mm) Size class (mm)

10 10

8 Lauderdale 8 Mortimer Bay

6 6 n = 80 (s) n = 20 (s)

n = 121 (w) Frequency 4 4 n = 30 (w) Frequency 2 2

0 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm) Size class (mm)

10 10

8 8 Orielton Lagoon Pipeclay Lagoon

6 6 n = 26 (s) n = 64

4 n = 47 (w) Frequency 4 Frequency

2 2

0 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm) Size class (mm)

10

8 South Arm 120 Spring 2006 6 n = 44 100

40 Summer 2007 20 4 0 10-14 15- 20-24 25- 30-34 35- Frequency Winter 2007 19 29 39 2

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm)

Figure 22 Size frequency histograms for the other bivalve species (pooled) in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable.

52 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Barilla Bay Five Mile 100 100

80 80

y 60 y 60 Barilla Bay Five Mile Beach n = 44 (s) 40 40 n = 28 Frequenc Frequenc n = 50 (w) 20 20

0 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 Size class (mm) Size class (mm) Lauderdale Mortimer Bay 100 100

80 80

y 60 y 60 Lauderdale Mortimer Bay n = 80 (s) 40 40 n = 20 (s) Frequenc n = 121 (w) Frequenc n = 30 (w) 20 20

0 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 Size class (mm) Size class (mm)

Orielton Pipeclay Lagoon 100 100

80 80 Orielton Lagoon Pipeclay Lagoon y 60 n = 26 (s) y 60 n = 47 (w) n = 64 40 40

Frequenc Frequenc

20 20

0 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 Size class (mm) Size class (mm)

South Arm Bay 100

80

y 60 South Arm n = 44 120 Spring 2006 40 100

Frequenc 40 Summer 2007 20 20 0 10-14Winter15- 20-24 25- 30-34 35-2007 19 29 39 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 Size class (mm)

Figure 23 Size frequency histograms for the polychaete Nephtys australiensis in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable.

53 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Barilla Bay Five Mile 50 50

40 40

y y 30 Barilla Bay 30 Five Mile Beach

20 n = 44 (s) 20 Frequenc Frequenc n = 28 n = 50 (w) 10 10

0 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 Size class (mm) Size class (mm)

Lauderdale Mortimer Bay 50 50

40 40

y y 30 Lauderdale 30 Mortimer Bay n = 80 (s) 20 20 n = 20 (s) Frequenc n = 121 (w) Frequenc n = 30 (w) 10 10

0 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 Size class (mm) Size class (mm)

Orielton Pipeclay Lagoon 50 50

40 40 y 30 y 30 Orielton Lagoon Pipeclay Lagoon 20 n = 26 (s) 20 n = 64

Frequenc Frequenc n = 47 (w) 10 10

0 0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 Size class (mm) Size class (mm) South Arm Bay 50

40 120 Spring 2006 100 y 30 South Arm 40 Summer 2007 20

0 20 10-14Winter 15- 20-24 25- 30-34 35-2007 19 29 39 Frequenc n = 44 10

0

10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 Size class (mm)

Figure 24 Size frequency histograms for the polychaete Leitoscoloplos normalis in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable.

54 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Barilla Bay Five Mile 90 90 80 80 70 70

y 60 y 60 50 Barilla Bay 50 Five Mile Beach 40 n = 44 (s) 40 n = 28 Frequenc

Frequenc 30 n = 50 (w) 30 20 20 10 10 0 0

10-14 25-29 40-44 55-59 70-74 85-89 10-14 25-29 40-44 55-59 70-74 85-89 100-104 115-119 130-134 145-149 160-164 175-179 190-194 205-209 100-104 115-119 130-134 145-149 160-164 175-179 190-194 205-209 Size class (mm) Size class (mm)

Lauderdale Mortimer Bay 90 90 80 80 70 70

y 60 y 60 50 Lauderdale 50 Mortimer Bay 40 40 n = 80 (s) n = 20 (s) Frequenc 30 Frequenc 30 n = 121 (w) n = 30 (w) 20 20 10 10 0 0

10-14 25-29 40-44 55-59 70-74 85-89 10-14 25-29 40-44 55-59 70-74 85-89 100-104 115-119 130-134 145-149 160-164 175-179 190-194 205-209 100-104 115-119 130-134 145-149 160-164 175-179 190-194 205-209 Size class (mm) Size class (mm)

Orielton Pipeclay Lagoon 90 90 80 80 70 70

y 60 y 60 50 Orielton Lagoon 50 Pipeclay Lagoon 40 40 n = 26 (s) Frequenc Frequenc n = 64 30 30 20 n = 47 (w) 20 10 10 0 0

10-14 25-29 40-44 55-59 70-74 85-89 10-14 25-29 40-44 55-59 70-74 85-89 100-104 115-119 130-134 145-149 160-164 175-179 190-194 205-209 100-104 115-119 130-134 145-149 160-164 175-179 190-194 205-209 Size class (mm) Size class (mm) South Arm Bay 90 80 70 y 60 120 Spring 2006 50 South Arm 100 40 40 Summer 2007 20

Frequenc 30 0 n = 44 10-14Winter15- 20-24 25- 30-34 35-2007 19 29 39 20 10 0

10-14 25-29 40-44 55-59 70-74 85-89 100-104 115-119 130-134 145-149 160-164 175-179 190-194 205-209 Size class (mm)

Figure 25 Size frequency histograms for the polychaete Olganereis edmonsi in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable.

55 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Barilla Bay Five Mile 30 30

25 25

y 20 y 20 Barilla Bay 15 15 Five Mile Beach n = 44 (s) n = 28 Frequenc 10 Frequenc 10 n = 50 (w) 5 5

0 0

10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 100-104 110-114 120-124 130-134 140-144 150-154 100-104 110-114 120-124 130-134 140-144 150-154 Size class (mm) Size class (mm) Mortimer Bay Lauderdale 30 30

25 25

y 20 y 20

15 Mortimer Bay 15 Lauderdale n = 20 (s) n = 80 (s)

Frequenc 10 Frequenc 10 n = 30 (w) n = 121 (w) 5 5

0 0

10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94

100-104 110-114 120-124 130-134 140-144 150-154 100-104 110-114 120-124 130-134 140-144 150-154 Size class (mm) Size class (mm)

Orielton Pipeclay Lagoon 30 30

25 25 y 20 y 20 Orielton Lagoon Pipeclay Lagoon 15 15

Frequenc n = 26 (s) Frequenc 10 10 n = 64 n = 47 (w) 5 5 0 0

10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 100-104 110-114 120-124 130-134 140-144 150-154 100-104 110-114 120-124 130-134 140-144 150-154 Size class (mm) Size class (mm)

South Arm Bay 30

25

y 20 120 Spring 2006 South Arm 100 15

40 Summer 2007 20

Frequenc 10 0 n = 44 10-14Winter15- 20-24 25- 30-34 35-2007 19 29 39 5

0

10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 100-104 110-114 120-124 130-134 140-144 150-154 Size class (mm)

Figure 26 Size frequency histograms for other polychaetes (pooled) in each bay, with data provided for the three seasons surveyed. n = number of core samples, with separate values for spring/summer (s) and winter (w) where applicable.

56 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 12 Mean sizes (mm) of prey species in each bay based on measured individuals ≥ 10 mm in grid samples. Red highlighted values indicate surrogate data based on non-grid sites where grid samples contained no individuals ≥ 10 mm.

Spring 2006 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 15.6 16.3 19.5 22.8 17.1 20.3 23.3 Katelysia scalarina Bivalvia (Mollusca) 23.4 23.4 20.5 31.3 N/A 26.4 28.9 Bivalves – Other Bivalvia (Mollusca) 34.1 10.5 35.6 16.3 21.4 10.4 38.8 Nephtys australiensis Polychaete (Annelida) 19.8 36 21.5 22.5 12.7 21.6 15.6 Leitoscoloplos normalis Polychaete (Annelida) 16.3 18.7 15.3 27.5 10 18.8 19.9 Olganereis edmonsi Polychaete (Annelida) 34 31 27 16 N/A 16.8 21.3 Polychaetes – Other Polychaete (Annelida) 23.7 23.1 27.6 39.7 12.1 17.1 16.3 Salinator fragilis Gastropoda (Mollusca) - - 11.6 - - 10.6 10.3

Summer 2007 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 14.3 17.1 19 21.4 17.6 20.7 24 Katelysia scalarina Bivalvia (Mollusca) 26.3 21 15.5 16.6 N/A 11.4 31.2 Bivalves – Other Bivalvia (Mollusca) 19.5 10 23.5 36.7 N/A 10.1 14 Nephtys australiensis Polychaete (Annelida) 25.4 N/A 15.2 21 24.6 24.1 21.1 Leitoscoloplos normalis Polychaete (Annelida) N/A 35.3 11.5 10.5 N/A 22.7 16.4 Olganereis edmonsi Polychaete (Annelida) 32 22 39.8 19.2 N/A 24.5 19.1 Polychaetes – Other Polychaete (Annelida) 25 19.4 38.7 34 57 37.3 21.6 Salinator fragilis Gastropoda (Mollusca) - - 11.8 - - 12.3 10.6

Winter 2007 - Species Taxonomic Group B F L M O P S Anapella cycladea Bivalvia (Mollusca) 14.4 16.1 18.4 25.7 19.3 19.9 21.1 Katelysia scalarina Bivalvia (Mollusca) 20.3 22.6 18.3 20.3 N/A 23.9 29.1 Bivalves – Other Bivalvia (Mollusca) 20.8 10 23 20.4 27.5 10.4 26.4 Nephtys australiensis Polychaete (Annelida) 30 N/A 19.8 16 33 25 18.3 Leitoscoloplos normalis Polychaete (Annelida) 25.6 N/A 26 27 N/A 28 53 Olganereis edmonsi Polychaete (Annelida) 73 33 70 58 14 33 52.4 Polychaetes – Other Polychaete (Annelida) 27 20 27 21 23 23 36.2 Salinator fragilis Gastropoda (Mollusca) - - 11.5 - - 11.7 11.5

The polychaete Olganereis edmonsi exhibited a major recruitment event at South Arm demonstrated by a spike in numbers during summer, however like Leitoscoloplos normalis, demonstrated reduced densities in the following winter survey. These data suggest that some polychaete species exhibit fast growth rates and large fluctuations in density over short periods of time. Olganereis edmonsi was common and included animals over a wide size range at Lauderdale, Mortimer Bay and Pipeclay Lagoon as well as South Arm, whilst contributing less to prey counts at Barilla Bay, Five Mile Beach and Orielton Lagoon (Figure 25). Mean size of this species was highest at Lauderdale in spring and summer, whilst in winter it achieved high mean sizes at Barilla Bay, Lauderdale, Mortimer Bay and South Arm. The data for the latter three locations are considered most accurate since they are based on large sample sizes, whilst only two individuals were included in calculations for Barilla Bay (see Figure 25). Additional (pooled) polychaete species contributed to the potential prey resource in all bays, with recent recruitment recorded at all locations, particularly at Pipeclay Lagoon during spring (Figure 26). Occasional very large individuals up to ~200 mm were recorded, whilst the highest mean sizes for pooled ‘other’ polychaetes were recorded at Mortimer Bay and Lauderdale in spring and summer, as well as Pipeclay Lagoon in summer, and at South Arm in Winter (Table 12).

57 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Size frequency histograms were not constructed for the gastropod Salinator fragilis, since all specimens ≥ 10 mm fell in the 10-14 mm size category. Mean sizes were calculated for the three bays where individuals were measured; Lauderdale, South Arm and Pipeclay Lagoon (southern end only; Zone 3 in Figure 15g). Mean size was fairly uniform across the three bays in winter, whilst data for other seasons suggested a smaller size at South Arm (Table 12).

Sediment characteristics are an important determinant of benthic infauna community composition and were investigated in conjunction with the spring invertebrate surveys. Redox potential measurements, particle size distributions and core descriptions were performed for approximately every second invertebrate sampling site in each bay. The raw data collected have been presented in the appendices of the estuarine and marine ecology technical report (Aquenal 2008b) and are not repeated here. Whilst that report did also provide an interpretation of the results of the sediment analyses in relation to community health indices, a summary of results is also included here to facilitate interpretation of the wader prey species data.

Core descriptions indicated that sediments in most bays consisted of brown sand at the surface and grey sand from depths of ~ 20 mm, with the exception of grey mud (silt) being recorded at the surface and in deeper sediments at Orielton Lagoon. There was also some evidence of finer sediments at shallow depths at Barilla Bay, and occasional black streaks were recorded in deeper sections of cores from most bays, suggesting anoxic conditions at depth. Sediment particle size reflects the nature of sediment inputs resulting from local geology or the broader catchment, and also levels/consistency of water flow. Sites located higher in estuaries and less exposed to wave action accumulate fine sediments, while those exposed to greater wave action and less direct catchment inputs have coarser sediments.

The results of particle size analyses and redox measurements are presented as box plots at sediment depths of 1 cm, 4 cm and 10 cm (or deepest depth that probe could be penetrated, up to 10 cm) in Figure 27 and Figure 28 respectively. The boxes define the 25th and 75th percentiles separated by the median value, whilst the box ‘whiskers’ reflect the minimum and maximum values except where there are outliers. Outside (X) and far outside (O) values are indicated and whiskers adjusted to extend a maximum of 1.5 times the inter-quartile range where these outliers were present.

In shallow sediments surveyed in the current study, low levels of coarse material (>2 mm) were recorded across the entire study area with average values ranging from 1% at Mortimer Bay to 4.9 % at Pipeclay Lagoon, and Lauderdale recording 3.3%. In most bays, there were occasional pockets of coarse material which comprised up to ~ 10-20% of the sediment samples, accounting for some of the higher values reflected in Figure 27. Percentage contributions of coarse sand (2->0.5 mm) were also low, ranging from an average of 0.8% at Orielton Lagoon and South Arm to 3.5% at Five Mile Beach, while Lauderdale recorded just 1%. Again, there were pockets of higher volumes of coarse sand, particularly at Barilla Bay, Five Mile Beach and Pipeclay Lagoon (Figure 27). Across both of these coarse size categories, Five Mile Beach recorded the highest average contribution (7.8%), followed by Pipeclay Lagoon (7.1%), while Lauderdale recorded 4.3%, and South Arm and Orielton Lagoon recorded the lowest values of all bays sampled (1.9% and 2.5% respectively).

Fine-medium sands (0.5-0.063 mm) formed the majority of the sediment, with percentage contribution averaging between 88% and 97% in most bays but declining to 73% in Orielton Lagoon. Relative to other areas, this lagoon recorded a significantly higher percentage of fine material (≤0.063 mm) (Figure 27), averaging at 24% and ranging from 15-33% across sites surveyed. Elsewhere, the contribution of fine silt/clay material was low and varied from an average of 0% at Mortimer Bay to 7.2% at Lauderdale. Similar to Mortimer Bay, most sites at Five Mile Beach and Pipeclay Lagoon recorded no fine silty material, but one site sampled at each location recorded an elevated value (~30%) thus influencing the mean values. Lauderdale and Barilla Bay were similar in recording fairly widespread low levels of fine material, with occasional elevated values at one or two sites.

58 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

25

20 >2mm

15

10 5 % Volume 0 B F L M O P SA

15 2->0.5mm 10

5 % Volume

0 B F L M O P SA

100 90 80 70 60

% Volume 50 0.5->0.063mm 40 30 B F L M O P SA

60 ≤0.063mm 50 40 30 20

% Volume 10 0

B F L M O P SA

Bay Figure 27 Box plots for particle size categories (>2 mm = coarse material - e.g. gravel, 2 mm–>0.5 mm = coarse sand, 0.5 mm->0.063 mm = fine to medium sand, ≤0.063 mm = silt/clay) at sites in each bay (refer to Bay name abbreviations in the Figure 28 caption).

59 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Redox potential values indicate the level to which sediments are oxygenated, with negative values indicative of anoxia. Anoxic conditions at the sediment surface or in very shallow sections of the sediment profile are generally associated with organic enrichment, however many sediments quickly become anoxic at depth due to reduced flushing. Measurements recorded here at 1 cm depth were consistently high (>400 mV) at Pipeclay Lagoon, Five Mile Beach and South Arm but were lower and more variable in other bays. Lowest values were recorded at Orielton Lagoon and Barilla Bay, the areas most affected by freshwater and catchment inputs, as well as at Mortimer Bay (Figure 28).

At 4 cm depth, values remained positive and showed a high level of overlap amongst bays, although lower median values were recorded at Orielton Lagoon, South Arm and Mortimer Bay. At Lauderdale, only one site just south of the proposed development site recorded a negative value at 4 cm depth. However, at 10 cm depth, median redox values in most bays were negative, with values as low as nearly -400 mV recorded at some Lauderdale sites. This is consistent with the observation of black streaks in cores noted above. At Lauderdale, 15 of 20 cores collected recorded negative values, reflecting widespread anoxia at 10 cm depth. The least anoxic values at this depth were in fact recorded at Orielton Lagoon. The reason for this is difficult to infer, particularly as catchment inputs and reduced tidal flows in the lagoon would be expected to increase the level of anoxia. It may be that the sandflats there remain exposed to air for longer periods and hence remain oxic to greater depths.

When relating the above sediment and prey species results, it is clear that Orielton Lagoon is differentiated from other bays on the basis of finer sediments and reduced densities of main prey species, particularly the bivalve Katelysia scalarina and polychaetes Olganereis edmonsi and Leitoscoloplos normalis. Whilst increasing the survey area in the lagoon during winter to improve coverage of the intertidal sandflat resulted in higher counts of prey species, density estimates were depressed compared with other bays during all seasons.

Sediment profiles in other bays were similar and do not provide a strong basis for explaining variation in prey species densities, although there are some similarities between patterns of variation in sediment characteristics and prey assemblages. For example, Five Mile Beach and Pipeclay Lagoon had very similar sediment profiles, with approximately 7-8% coarse material/sand, 90% fine-medium sand and an absence of fine silt/clay material except at occasional sites. MDS plots indicated that Five Mile Beach samples were differentiated from others due to a higher density of the bivalve Wallucina assimilis and lower density of certain polychaete species; however the bay with the most similar assemblages to Five Mile Beach was Pipeclay Lagoon (Figure 16 and Figure 18).

In Ralphs Bay, sediments were generally low in coarse material/sand and fines, with medium-fine sands dominating. The only differences amongst Ralphs Bay locations were a higher level of coarse material at Lauderdale due to rubble at the northern end, and a lower level of fines at Mortimer Bay which may be because of its greater exposure to prevailing winds and hence wind/wave disturbance. The three bays which recorded very little fine material (< 0.063 mm), Pipeclay Lagoon, Five Mile Beach and Mortimer Bay tended to occupy the left hand side of the MDS plots (Figure 16 and Figure 18), although Mortimer Bay summer and winter samples including individuals of all sizes were more similar to the ‘central’ group that incorporated Lauderdale. While SIMPER analysis suggests that bays on the left side were generally characterised by reduced densities of Anapella cycladea, this was not true of Five Mile Beach and there is no clear relationship between prey species density and the absence of fine < 0.063 mm sedimentary material.

60 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

500 400 300 200 100 0 -100 1 cm Depth -200 Redox Potential (mV) B F L M O P SA

400 300 200 100 0 -100 4 cm Depth -200 Redox Potential (mV) B F L M O P SA

500 400 300 10 cm Depth 200 100 0 -100 -200 -300

Redox Potential (mV) -400 B F L M O P SA Bay

Figure 28 Box plots for redox potential values at 1 cm, 4 cm and ~10 cm (or greatest depth possible to a maximum of 10 cm) depths in sediment core samples (Bays: B = Barilla Bay; F = Five Mile Beach; L = Lauderdale; M = Mortimer Bay; O = Orielton Lagoon; P = Pipeclay Lagoon; S = South Arm).

61 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

4.2.2 Variation at Lauderdale

The complete invertebrate dataset for Lauderdale is included in Appendix 11 of the estuarine and marine ecology technical report prepared for the IIS (Aquenal 2008b) and not repeated here, while mean prey species abundance data per core sample for the three survey zones N1, N2 and S (N1 = original proposed development site, N2 = northern part of sandflats south of N1, S = southern sandflats; see Section 3.3.2) are provided below in Table 13 for each season surveyed. As described in Section 4.2.1 for comparisons amongst bays, prey species were limited to those targeted by the invertebrate surveys and included a total of thirteen prey species. For animals ≥ 10 mm (see later, Table 16), which better reflect available wader prey resources than datasets including individuals of all sizes, data is again included for pooled groupings of other less common bivalve and polychaete species.

Mean densities are indicated in Table 13 on the basis of grid sites only, and on the basis of grid sites combined with additional sites sampled to target particular habitats or survey areas as described in Section 3.3.2. These data do not take into consideration the size of the individuals, and hence may include individuals outside the size range observed in wader diets. As indicated in Section 4.2.1, they are therefore more indicative of total ‘potential’ prey resources through the year rather than total available resources at the particular time of each survey.

On the basis of data for individuals of all sizes (Table 6), and considering both the dataset for grid sites and the dataset for combined grid sites/additional sites, average number of individuals across all prey species per core and survey zone ranged from 7.0 to 14.3 in spring, 18.2 to 35.79 in summer and 14.32 to 24.1 in winter. In spring and winter, the mean lowest density was consistently recorded in N1, whiles values at N2 and S were comparable. N1 also recorded the lowest densities in summer although counts were similar to those recorded at S, with much higher counts recorded at N2. Across all three seasons, N2 recorded the highest average density of prey species individuals (24.0), followed by S (19.7-20.1) and N1 (13.4-16.1) (Table 13).

Pooled data for taxonomic groups of prey species (Table 14) reveals that highest densities of bivalve prey species were recorded at S in all seasons, whilst the highest densities of polychaetes were consistently recorded at N2. Spatial variation in crab densities varied seasonally, with highest numbers at N2/S in spring, N1 in summer and S in winter. The gastropod Salinator fragilis recorded highest densities at N2 in spring and summer and at S in winter.

When the same dataset was pooled across seasons, it was again apparent that densities of bivalves were highest overall at S, while densities of polychaetes were highest at N2 (Table 15). Salinator fragilis reached highest densities overall at N2, closely followed by S, while crab densities were very similar in the three survey zones and varied between the two datasets containing either grid sites only or combined grid/additional sites. At S, the high density of bivalves was due to elevated numbers of Anapella cycladea, whilst the other common bivalve at Lauderdale, Katelysia scalarina, was most abundant in N2 followed by N1. The high densities of polychaetes at N2 were due to elevated numbers of both Nephtys australiensis and Olganereis edmonsi in summer and winter, and slightly higher counts of Leitoscoloplos normalis in spring compared with the other two survey zones (Table 13, Table 15). N1 also recorded high densities of polychaetes, with N. australiensis and O. edmonsi recording elevated counts in summer and winter.

For the Pied Oystercatcher, the bivalves Anapella cycladea and Katelysia scalarina together with the polychaetes comprised ~90% of the total count of observed dietary items for Pied Oystercatchers during foraging surveys (Table 1). The combined average density of these species was greatest at N2 (45.9), with lower and comparable values recorded at N1 (32.0-38.2) and S (33.3-34.4) (Table 15).

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Table 13 Mean abundance per core sample of wader prey species in each Lauderdale survey zone (N1, N2 and S) including all individuals collected in core samples.

Spring 2006 - Species Taxonomic Group Grid sites only Including additional sites N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 1.50 2.96 3.94 4.13 6.28 Katelysia scalarina Bivalvia (Mollusca) 1.03 1.21 0.56 0.84 1.00 Tellina deltoidalis Bivalvia (Mollusca) 0.12 0.04 0.33 0.08 0.22 Eumarcia fumigata Bivalvia (Mollusca) 0.06 0.00 0.00 0.03 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 0.22 0.00 0.67 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.00 0.06 0.00 0.03 Nephtys australiensis Polychaeta (Annelida) 1.29 1.50 1.44 1.14 1.19 Leitoscoloplos normalis Polychaeta (Annelida) 0.91 2.86 2.06 1.75 1.72 Olganereis edmonsi Polychaeta (Annelida) 0.03 0.04 0.06 0.05 0.06 Paragrapsus gaimardii Decapoda (Crustacea) 0.00 0.11 0.06 0.05 0.11 Mictyris platycheles Decapoda (Crustacea) 0.00 0.00 0.00 0.00 0.00 Salinator fragilis Gastropoda (Mollusca) 2.06 3.96 3.33 2.00 3.06 Total 7.00 12.68 12.06 10.06 14.33 Summer 2007 - Species Taxonomic Group N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 1.15 3.07 6.72 4.63 7.03 Katelysia scalarina Bivalvia (Mollusca) 1.15 1.86 0.67 0.95 0.75 Tellina deltoidalis Bivalvia (Mollusca) 0.03 0.07 0.17 0.02 0.17 Eumarcia fumigata Bivalvia (Mollusca) 0.94 0.11 0.00 0.50 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 0.89 0.00 1.11 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.25 0.00 0.00 0.00 Nephtys australiensis Polychaeta (Annelida) 3.62 5.82 1.44 3.38 1.44 Leitoscoloplos normalis Polychaeta (Annelida) 0.56 0.89 2.17 0.83 1.39 Olganereis edmonsi Polychaeta (Annelida) 7.71 7.00 0.83 5.17 1.03 Paragrapsus gaimardii Decapoda (Crustacea) 0.18 0.00 0.06 0.20 0.36 Mictyris platycheles Decapoda (Crustacea) 0.00 0.07 0.00 0.00 0.00 Salinator fragilis Gastropoda (Mollusca) 3.50 16.64 11.28 5.53 8.08 Total 18.82 35.79 24.22 21.20 21.36 Winter 2007 - Species Taxonomic Group N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 1.07 2.46 8.57 4.32 8.03 Katelysia scalarina Bivalvia (Mollusca) 2.17 3.41 1.09 1.73 1.22 Tellina deltoidalis Bivalvia (Mollusca) 0.02 0.29 0.13 0.02 0.13 Eumarcia fumigata Bivalvia (Mollusca) 0.07 0.00 0.02 0.04 0.02 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 0.54 0.00 1.28 Soletellina biradiata Bivalvia (Mollusca) 0.07 0.13 0.00 0.04 0.00 Nephtys australiensis Polychaeta (Annelida) 6.20 5.98 1.59 5.71 1.53 Leitoscoloplos normalis Polychaeta (Annelida) 0.58 0.48 1.15 0.73 0.92 Olganereis edmonsi Polychaeta (Annelida) 3.00 6.36 1.00 2.79 0.80 Paragrapsus gaimardii Decapoda (Crustacea) 0.03 0.09 0.11 0.10 0.11 Mictyris platycheles Decapoda (Crustacea) 0.02 0.00 0.00 0.01 0.00 Salinator fragilis Gastropoda (Mollusca) 1.10 4.27 9.89 1.37 9.31 Total 14.32 23.46 24.09 16.88 23.34 Mean total per season 13.38 23.98 20.12 16.05 19.68

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Table 14 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each Lauderdale survey zone (N1, N2 and S) including all individuals collected.

Grid sites only Including additional sites Season Taxonomic Group N1 N2 S N1 S Spring 2006 Total bivalves 2.71 4.21 5.11 5.08 8.19 Total polychaetes 2.24 4.39 3.56 2.94 2.97 Total crabs 0.00 0.11 0.06 0.05 0.11 Total gastropods 2.06 3.96 3.33 2.00 3.06

Summer 2007 Total bivalves 3.26 5.36 8.44 6.09 9.06 Total polychaetes 11.88 13.71 4.44 9.38 3.86 Total crabs 0.18 0.07 0.06 0.20 0.36 Total gastropods 3.50 16.64 11.28 5.53 8.08

Winter 2007 Total bivalves 3.38 6.29 10.35 6.17 10.67 Total polychaetes 9.78 12.82 3.74 9.23 3.25 Total crabs 0.05 0.09 0.11 0.11 0.11 Total gastropods 1.10 4.27 9.89 1.37 9.31

Table 15 Pooled mean abundances per core sample across seasons for wader prey species in each Lauderdale survey zone (N1, N2 and S) including all individuals collected.

Grid sites only Including additional sites Species Taxonomic Group N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 3.71 8.50 19.23 13.07 21.34 Katelysia scalarina Bivalvia (Mollusca) 4.34 6.48 2.31 3.53 2.97 Tellina deltoidalis Bivalvia (Mollusca) 0.16 0.39 0.63 0.12 0.51 Eumarcia fumigata Bivalvia (Mollusca) 1.07 0.11 0.02 0.58 0.02 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 1.65 0.00 3.06 Soletellina biradiata Bivalvia (Mollusca) 0.07 0.38 0.06 0.04 0.03 Total bivalves 9.35 15.86 23.90 17.34 27.92 Total A. cycladea and K. scalarina 8.06 14.98 21.54 16.60 24.31

Nephtys australiensis Polychaeta (Annelida) 11.11 13.30 4.48 10.23 4.17 Leitoscoloplos normalis Polychaeta (Annelida) 2.05 4.23 5.37 3.31 4.03 Olganereis edmonsi Polychaeta (Annelida) 10.74 13.39 1.89 8.01 1.88 Total polychaetes 23.90 30.93 11.74 21.55 10.08

Mictyris platycheles Decapoda (Crustacea) 0.02 0.07 0.00 0.01 0.00 Paragrapsus gaimardii Decapoda (Crustacea) 0.21 0.20 0.22 0.35 0.58 Total crabs 0.23 0.27 0.22 0.36 0.58

Salinator fragilis Gastropoda (Mollusca) 6.66 24.88 24.50 8.90 20.45 Total gastropods 6.66 24.88 24.50 8.90 20.45

Species contributing Total A. cycladea and ~90% of Pied K. scalarina and Oystercatcher prey polychaetes 31.96 45.91 33.28 38.15 34.39

64 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

The results of multi-dimensional scaling (MDS) analysis using mean seasonal data for each survey zone, incorporating all prey species individuals (i.e. all sizes) in core samples, are presented in the MDS plot in Figure 29. The stress statistic of 0.07 indicates reliable depictions of similarities amongst bays and seasons. There was evidence of similar seasonal variation at N1 and N2, with the spring season differentiated from the other two seasons surveyed. SIMPER analysis indicated that this was due to increased densities of Olganereis edmonsi and Nephtys australiensis, and to a lesser extent Salinator fragilis, in summer and winter. There was less evidence of seasonal variation at S, with a high level of similarity between the three seasonal datasets. The S survey zone was differentiated from N1 and N2 on the basis of elevated densities of Anapella cycladea. Note that Figure 29 only includes data for grid sites; however a similar result was obtained when the additional sites were included in the analysis.

Stress: 0.07 N1-Sp N1

N2-Sp N1-Su N1-W N2

S-Sp N2-W

S-W S N2-Su S-Su

Figure 29 MDS plot of mean densities of prey species for Lauderdale survey zones in each season surveyed, based on grid survey sites (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007).

Further MDS analyses were conducted using grid sites and additional sites surveyed to assess relationships of wader prey species with benthic habitat type and tide height, with the resulting stress statistic values ranging from 0.14 to 0.17 indicating reliable depictions of similarities (Figure 30, Figure 32). Habitats at Lauderdale are dominated by sand, with rocky habitats primarily limited to the very northern part of the proposed development site (Figure 3) and seagrass only found in the very southern sandflats near East Marsh Lagoon (Figure 4). The MDS plots in Figure 30, which distinguish amongst the different habitat types sampled, therefore include a lower representation of rocky and seagrass habitats compared with sandy habitats by virtue of availability. The seasonal plots suggest that the predominant sand habitat encompassed the majority of prey assemblage types at Lauderdale, although there were several outlying values for sites with seagrass, rock/sand and dense rocky rubble habitats. The four seagrass sites grouped on one side of the plot, with SIMPER analysis indicating that this habitat type had higher densities of Anapella cycladea than other habitats. The next highest densities of A. cycladea were recorded at sand/pebble and then dense rubble habitats at N1, with the relatively high numbers recorded explaining why these two habitats also grouped on one side of the plot with seagrass sites. The sand/rock sites were more scattered in the plot and included occasional outliers that were different to all other sites surveyed. On the basis of SIMPER analysis, these outliers can be attributed to depauperate prey species assemblages, with some samples for example containing no Nephtys australiensis and reduced densities of other species such as Leitoscoloplos normalis and Katelysia scalarina.

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Stress: 0.14

Spring 2006

Stress: 0.17 N1-S N1-R Summer 2007

N1-P N1-D

N2-S S-S

S-G

Stress: 0.15 Winter 2007

Figure 30 MDS plots of mean densities of prey species for habitats sampled in each Lauderdale survey zone (Habitats: S = unvegetated sand, G = seagrass, R = sand interspersed with rocks, P = sand interspersed with pebbles, D = dense rocky rubble).

66 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

In order to facilitate interpretation of data relating to tide height, the approximate boundaries of the four tidal height categories allocated in the current study are illustrated at Lauderdale in Figure 31, with category 1 representing the highest shore area immersed for the shortest period of the tidal cycle, and category 4 immersed for the longest. These categories were determined using the approach outlined in Section 3.3.1. The MDS analyses revealed some trends in prey species assemblages on the basis of frequency of tidal immersion. There was overlap in assemblages from the four tidal height categories, particularly in spring but to a far lesser extent in winter when a much larger number of sites was surveyed (Figure 32). Given that sites from the same tidal height but different survey zones tended to group together, this suggests that tide height has a greater role in determining the composition of prey species than does location on the sandflat (N1, N2, S).

SIMPER analysis indicated that sites highest on the shore and therefore immersed in water for the shortest period had the highest densities of Anapella cycladea and Salinator fragilis, as found in analyses for the various bays surveyed (Section 4.2.1). The differentiation of tide category 2 sites from the lowest shore sites (tide categories 3 and 4), which was most pronounced during winter, was due to higher densities of Katelysia scalarina, Olganereis edmonsi and S. fragilis, and slightly lower densities of Nephtys australiensis. The polychaete O. edmonsi became highly abundant in summer and winter, with this species tending to reach highest densities in tidal height category 2, followed by category 3. This suggests that O. edmonsi may have a preference for intermediate shore levels at Lauderdale.

All of the above data analyses for survey zones at Lauderdale were based on the complete dataset for prey species, including animals of all sizes. Similar analyses are presented below that are limited to animals ≥ 10 mm to describe more accurately the prey species resources considered ‘available’ to waders at the time of the surveys. The species included in these analyses are the same as those described in Section 4.2.1 for comparisons of bays, with additional less common bivalves and polychaetes within the size range consumed by waders included in the data analyses and allocated to the pooled categories of ‘Bivalve – Other’ or ‘Polychaete – Other’. Mean abundances per sample of animals in each survey zone are indicated in Table 16; as described in Section 4.2.1, the totals for each bay exclude the gastropod Salinator fragilis since size data for this species were not collected in all bays or all parts of bays.

The average number of individuals across all prey species per core incorporating datasets for grid sites only and for grid sites/additional sites, and including all bivalves and polychaetes, ranged from 3.7 to 9.2 in spring, 3.2 to 7.9 in summer and 4.1 to 6.6 in winter (Table 16). As with data for individuals of all sizes, lowest total mean densities of prey species in grid samples were recorded at N1. However, when all additional sites targeting particular habitats and representative tide levels within survey zones were included in the analysis, N1 recorded comparable total prey species densities. The additional sites included some mixed rock/sand habitats unique to N1, and several of these habitats appear to boost prey numbers within the zone.

Consistent with data for individuals of all sizes, pooled data for taxonomic groups of prey species (Table 17) reveal that highest numbers of ≥ 10 mm bivalve prey species were recorded at S in all seasons. However, while N2 again recorded the highest densities of polychaetes in spring, numbers were comparable or higher at N1 in summer and winter and at S in summer. This suggests that a large portion of polychaetes at N2 in these seasons were < 10 mm and therefore potentially not available to waders as prey. Densities of ≥ 10 mm polychaetes were reduced at survey zone S in winter compared with the other two zones (Table 17). Contrasting with data for individuals of all sizes, the gastropod Salinator fragilis recorded highest densities at S in all seasons, rather than just in winter. This indicates that a larger portion of animals at N2 were < 10 mm and therefore potentially not available as prey. N1 recorded consistently low counts of ≥ 10 mm S. fragilis, particularly in winter.

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Figure 31 Tide height categories allocated at Lauderdale to assess variation in prey species composition with level of tidal inundation.

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Stress: 0.14

Spring 2006

Stress: 0.17 1N1 2N1

3N1 4N1

1N2 2N2

3N2 4N2

1S 2S

Summer 2007

Stress: 0.15

Winter 2007

Figure 32 MDS plots of mean densities of prey species of all sizes at different tide heights in each Lauderdale survey zone (Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore).

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Table 16 Mean abundance per core sample of prey species ≥ 10 mm length at the Lauderdale survey zones.

Spring 2006 - Species Taxonomic Group Grid sites only Including additional sites N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 1.30 2.88 3.67 4.13 6.11 Katelysia scalarina Bivalvia (Mollusca) 0.27 0.23 0.11 0.18 0.33 Tellina deltoidalis Bivalvia (Mollusca) 0.00 0.00 0.33 0.02 0.22 Eumarcia fumigata Bivalvia (Mollusca) 0.00 0.04 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 0.11 0.00 0.14 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.07 0.08 0.00 0.03 0.00 Nephtys australiensis Polychaeta (Annelida) 1.13 1.23 1.33 0.98 1.03 Leitoscoloplos normalis Polychaeta (Annelida) 0.67 1.42 1.22 1.18 1.14 Olganereis edmonsi Polychaeta (Annelida) 0.03 0.00 0.00 0.07 0.11 Polychaetes – Other * Polychaete (Annelida) 0.27 0.23 0.17 0.15 0.11 Salinator fragilis # Gastropoda (Mollusca) 0.27 0.15 0.28 0.17 0.31 Total (excl. #) 3.73 6.12 6.94 6.75 9.19 Total (excl. # and *) 3.40 5.81 6.78 6.57 9.08 Summer 2007 - Species Taxonomic Group N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 1.16 2.27 5.50 3.97 6.33 Katelysia scalarina Bivalvia (Mollusca) 1.00 1.81 0.44 0.76 0.58 Tellina deltoidalis Bivalvia (Mollusca) 0.03 0.08 0.17 0.02 0.17 Eumarcia fumigata Bivalvia (Mollusca) 0.03 0.04 0.00 0.02 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.08 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.00 0.08 0.00 0.00 0.00 Nephtys australiensis Polychaeta (Annelida) 0.78 0.58 0.50 0.63 0.33 Leitoscoloplos normalis Polychaeta (Annelida) 0.00 0.00 0.11 0.02 0.08 Olganereis edmonsi Polychaeta (Annelida) 0.09 0.23 0.33 0.08 0.39 Polychaetes – Other * Polychaete (Annelida) 0.06 0.00 0.06 0.06 0.06 Salinator fragilis # Gastropoda (Mollusca) 0.13 0.65 0.83 0.10 0.78 Total (excl. #) 3.16 5.15 7.11 5.55 7.94 Total (excl. # and *) 3.09 5.08 7.06 5.48 7.89 Winter 2007 - Species Taxonomic Group N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 0.64 1.35 3.74 3.50 4.55 Katelysia scalarina Bivalvia (Mollusca) 0.67 0.80 0.37 0.58 0.53 Tellina deltoidalis Bivalvia (Mollusca) 0.02 0.13 0.11 0.02 0.08 Eumarcia fumigata Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.03 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.06 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.03 0.06 0.00 0.02 0.00 Nephtys australiensis Polychaeta (Annelida) 2.10 1.43 0.13 1.89 0.17 Leitoscoloplos normalis Polychaeta (Annelida) 0.05 0.06 0.13 0.08 0.11 Olganereis edmonsi Polychaeta (Annelida) 0.48 0.76 0.09 0.45 0.08 Polychaetes – Other * Polychaete (Annelida) 0.10 0.15 0.04 0.07 0.05 Salinator fragilis # Gastropoda (Mollusca) 0.00 0.11 0.83 0.01 0.84 Total (excl. #) 4.10 4.78 4.61 6.61 5.59 Total (excl. # and *) 3.97 4.57 4.57 6.52 5.55 Mean total per season (excl. #) 3.66 5.35 6.22 6.30 7.58 Mean total per season (excl. # and *) 3.49 5.15 6.13 6.19 7.51

70 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 17 Pooled mean abundances per core sample for wader prey taxonomic groups by season in each Lauderdale survey zone (N1, N2 and S) on the basis of individuals ≥ 10 mm.

Including Grid sites only additional sites Season Taxonomic Group N1 N2 S N1 S Spring 2006 Total bivalves (all) 1.63 3.23 4.22 4.37 6.81 Total bivalves (excluding 'Bivalves - Other') 1.57 3.15 4.22 4.33 6.81 Total polychaetes (all) 2.10 2.88 2.72 2.38 2.39 Total polychaetes (excluding 'Polychaetes - Other') 1.83 2.65 2.56 2.23 2.28 Total gastropods 0.27 0.15 0.28 0.17 0.31

Summer 2007 Total bivalves (all) 2.22 4.35 6.11 4.76 7.08 Total bivalves (excluding 'Bivalves - Other') 2.22 4.27 6.11 4.76 7.08 Total polychaetes (all) 0.94 0.81 1.00 0.79 0.86 Total polychaetes (excluding 'Polychaetes - Other') 0.88 0.81 0.94 0.73 0.81 Total gastropods 0.13 0.65 0.83 0.10 0.78

Winter 2007 Total bivalves (all) 1.36 2.39 4.22 4.13 5.19 Total bivalves (excluding 'Bivalves - Other') 1.33 2.33 4.22 4.10 5.19 Total polychaetes (all) 2.74 2.39 0.39 2.49 0.41 Total polychaetes (excluding 'Polychaetes - Other') 2.64 2.24 0.35 2.42 0.36 Total gastropods 0.00 0.11 0.83 0.01 0.84

Table 18 Pooled mean abundances per core sample across seasons for wader prey species in each Lauderdale survey zone (N1, N2 and S) on the basis of individuals ≥ 10 mm.

Grid sites only Including additional sites Species Taxonomic Group N1 N2 S N1 S Anapella cycladea Bivalvia (Mollusca) 3.09 6.51 12.91 11.60 16.99 Katelysia scalarina Bivalvia (Mollusca) 1.94 2.83 0.93 1.52 1.45 Tellina deltoidalis Bivalvia (Mollusca) 0.05 0.21 0.61 0.06 0.47 Eumarcia fumigata Bivalvia (Mollusca) 0.03 0.08 0.00 0.02 0.00 Laternula tasmanica Bivalvia (Mollusca) 0.00 0.00 0.00 0.00 0.00 Wallucina assimilis Bivalvia (Mollusca) 0.00 0.00 0.11 0.00 0.17 Soletellina biradiata Bivalvia (Mollusca) 0.00 0.13 0.00 0.00 0.00 Bivalves – Other * Bivalvia (Mollusca) 0.10 0.21 0.00 0.06 0.00 Total bivalves (all) 5.21 9.97 14.55 13.25 19.08 Total bivalves (excluding *) 5.11 9.76 14.55 13.19 19.08 Nephtys australiensis Polychaeta (Annelida) 4.02 3.23 1.96 3.50 1.53 Leitoscoloplos normalis Polychaeta (Annelida) 0.72 1.48 1.46 1.28 1.33 Olganereis edmonsi Polychaeta (Annelida) 0.61 0.99 0.42 0.60 0.58 Polychaetes – Other # Polychaete (Annelida) 0.43 0.38 0.27 0.28 0.21 Total polychaetes (all) 5.78 6.08 4.11 5.66 3.66 Total polychaetes (excluding #) 5.35 5.70 3.85 5.38 3.44 Salinator fragilis Gastropoda (Mollusca) 0.39 0.92 1.94 0.27 1.93 Total gastropods 0.39 0.92 1.94 0.27 1.93 Species contributing Total A. cycladea and K. scalarina ~90% of Pied and polychaetes 10.81 15.42 17.94 18.78 22.10 Oystercatcher prey Total A. cycladea and K. scalarina and polychaetes (excl. #) 10.38 15.04 17.68 18.50 21.88

71 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

When the same dataset was pooled across seasons, it was again apparent that densities of bivalves were highest overall at S, while numbers increased markedly at N1 when the additional non-grid samples were included in the analysis (Table 18). The species responsible for high densities of bivalves at S, and increased numbers at N1 through inclusion of additional sites, was Anapella cycladea. As found for the dataset including individuals of all sizes, Katelysia scalarina reached highest densities in N2 followed by N1 when only ≥ 10 mm individuals were considered. Reduced densities of K. scalarina at S were due primarily to low numbers in the southern part of this zone (= zone S2, Harrison 2008), as densities were fairly comparable in the narrower northern section (= zone S1, Harrison 2008). Across all seasons, densities of polychaetes were highest at N2, despite not being highest in this zone during all seasons. N1 also recorded high densities of polychaetes, with Nephtys australiensis the most abundant species in this zone and at N2 and S. Salinator fragilis was most abundant overall at S, closely followed by N2, the reverse of results reported for individuals of all sizes. This is indicative of the higher proportion of animals ≥ 10 mm at S, while N1 recorded lower total numbers (Table 15) and lower numbers of ≥ 10 mm animals than N1 and S (Table 18).

For the Pied Oystercatcher, the bivalves Anapella cycladea and Katelysia scalarina together with the polychaetes comprised ~ 90% of the total count of items consumed by Pied Oystercatchers during foraging surveys (Table 1). Data for prey species of all sizes indicated that the combined average abundance of these species per core sample was greatest at N2 (Table 15), however results for ≥ 10 mm animals indicates highest numbers at S (Table 18). Whilst analysis of grid site samples suggested lowest densities at N1, inclusion of the additional survey sites found that prey species densities at N1 were intermediate to those for N2 and S. This indicates that some of the areas targeted by the additional sampling have higher prey densities than the uniform grid samples, and suggests that the variety of habitats at N1 may help to increase the availability of prey.

The results of multi-dimensional scaling (MDS) analysis using mean seasonal data for each survey zone, incorporating only ≥ 10 mm individuals and only the grid survey sites, are presented in the MDS plot in Figure 33. The stress statistic of 0.08 indicates reliable depictions of similarities amongst survey zones and seasons. As found in the plot for data containing animals of all sizes, there was considerable overlap of prey assemblages at N1 and N2, whilst S formed a distinct subgrouping. SIMPER analysis indicated that S was again differentiated primarily because of higher densities of Anapella cycladea and Salinator fragilis, while slightly lower densities of Nephtys australiensis and Katelysia scalarina also contributed to differentiation of this survey zone. The patterns of similarity between seasonal datasets for ≥ 10 mm individuals at N1 and N2 are different to those described for the ‘all sizes’ dataset. In this case similarity levels were related more to season than location, since within-season variation was less than inter-seasonal variation between the two survey zones. This is consistent with findings for spring using all individuals, however the same analysis found patterns of similarity in winter and summer to be more closely related to location (N1 or N2) than season (Figure 29). Seasonal variation at these two survey zones using the ≥ 10 mm data can be attributed to a higher density of K. scalarina in summer, higher density of Leitoscoloplos normalis in spring, and a combination of reduced density of A. cycladea and increased density of N. australiensis in winter samples. This contrasts to some extent with species contributing to patterns of similarity in the dataset containing individuals of all sizes, and suggests that it is important to consider sizes available to the birds when assessing the composition of prey assemblages.

When the analysis was re-run including both grid and additional non-grid sites, the groupings in the resulting plot were more closely associated with survey zone location than described above. Zone S again formed a distinct grouping, but N1 did as well, while N2 was more seasonally variable (Figure 34). This modification to patterns of similarity was primarily due to higher densities of Anapella cycladea at the ‘additional’ sites surveyed at N1 in all seasons, whereby the plot provided a gradient in the density of this species, with higher, medium and lower densities at S, N1 and N2 respectively. N2 samples were similar to those at N1 in winter, but in other seasons they contained less A. cycladea, in summer they contained more Katelysia scalarina, and in spring they contained more Leitoscoloplos normalis.

72 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Stress: 0.08

N1-W N1

N1-Sp N2-Sp

N2 N2-W N2-Su

S-Su N1-Su S S-Sp S-W

Figure 33 MDS plot of mean densities of prey species for Lauderdale survey zones in each season surveyed on the basis of individuals ≥ 10 mm collected at grid sites (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007).

Stress: 0.08 S-W

S-Su N1 S-Sp

N1-Su

N1-W N2 N1-Sp N2-Su

N2-W

S N2-Sp

Figure 34 MDS plot of mean densities of prey species for Lauderdale survey zones in each season surveyed on the basis of individuals ≥ 10 mm collected at grid sites and additional non-grid sites (Seasons: Sp = Spring 2006; Su = Summer 2007; and W = Winter 2007).

73 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Further MDS analyses were conducted using grid sites and additional sites surveyed to assess relationships of wader prey species ≥ 10 mm with benthic habitat type and tide height, with the resulting stress statistic values ranging from 0.13 to 0.16 indicating reliable depictions of similarities (Figure 35, Figure 36). As indicated above, rocky and seagrass habitats are found in small areas of N1 and S respectively, whilst the dominant habitat type (sand) characterised most sites surveyed. The seasonal plots suggest that the predominant sand habitat encompassed the majority of prey assemblage types at Lauderdale although there were several outlying values for N1 sites with rock/sand and pebbles/sand habitats in spring (Figure 35). Habitats other than the predominant sand type grouped on one side of the plots and therefore only overlapped with a portion of the sand habitat sites. Patterns depicted in these habitat plots are relatively similar to those produced using data for all sizes of animals (Figure 30), with SIMPER analysis again indicating that the seagrass, sand/pebble and dense rubble habitats had higher mean densities of Anapella cycladea than the unvegetated sand sites. These habitats help to explain the higher density of A. cycladea at N1 and S once the additional non-grid sites were included in calculations of mean densities (Table 17, Table 18). They also had slightly lower densities of Nephtys australiensis than the majority of the sand sites. The sand/rock sites were more scattered in the plots and showed little differentiation from the sand sites in summer and winter. In spring, sites in this habitat formed a small cluster that overlapped with few other sites due to reduced densities of A. cycladea and N. australiensis and slightly higher densities of Leitoscoloplos normalis than all other habitats.

The MDS plots depicting similarities on the basis of tide height for the ≥ 10 mm dataset revealed a large degree of overlap between tide categories 2-4, whilst category 1 (highest on the shore), grouped on the right side of the seasonal plots (Figure 36). Sites from the same tide height category tended to group together, indicating that prey species composition was more closely related to tide level than to survey zone (N1, N2, S) on the Lauderdale sandflat. As found in the analyses for individuals of all sizes, SIMPER analysis indicated that sites highest on the shore had the highest densities of Anapella cycladea. The differentiation of tide category 2 sites from the lower shore sites recorded for analyses including all individuals, particularly in winter (Figure 32), was not recorded in the analyses limited to ≥ 10 mm animals. Category 2 sites still recorded higher densities on average of Olganereis edmonsi and Katelysia scalarina, and lower densities of Nephtys australiensis, but differences in numbers were small. This suggests that there is greater tidal variation in densities of small (< 10 mm) individuals of these species than in densities of larger individuals suitable as wader prey. Hence it appears that the primary differences in prey assemblages occur between the high shore category 1 area and the remaining lower part of the shore.

Mean sizes of main prey species and other pooled bivalves and polychaetes were calculated for each of the above tide height categories (1-4) across the entire Lauderdale sandflat on the basis of animals ≥ 10 mm (Table 19). Note that ‘N/A’ is indicated in the table where no ≥ 10 mm individuals of a particular species or pooled group were identified for the tide height category. All grid and non-grid sites were incorporated in calculations to maximise samples sizes for the different tide height categories. Anapella cycladea was generally only found in tide categories 1 and 2; the mean size of 35 mm indicated for tide category 3 in spring was based on one animal only and is therefore unlikely to provide accurate data on tidal variation in size. However there was a trend in this species for increased size lower in its tidal range during all seasons. Katelysia scalarina and other pooled bivalves were more widely distributed over the tidal range and exhibited no clear change in size in association with the tidal gradient.

Leitoscoloplos normalis individuals ≥ 10 mm were more frequently recorded in tide categories 1 and 2 (i.e. none in categories 3 and 4 in summer and winter) but this may reflect the lower general density of this species at Lauderdale and the greatest survey intensity in high shore areas as a result of additional sampling in benthic habitats limited to that shore level. The mean size of 40 mm in tide category 4 in spring was based on one animal and therefore has limited accuracy. There was no clear tidal gradient in size of this species or Nephtys australiensis. Olganereis edmonsi was not abundant in spring and hence data for that season is of limited value in determining tidal height variation in size. In summer and winter, when this species became abundant, there was a trend for this species to increase in size lower on the shore.

74 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Stress: 0.16 Spring 2006

Stress: 0.13 Summer 2007 N1S N1R

N1P N1D

N2S SS

SG

Stress: 0.14 Winter 2007

Figure 35 MDS plots of mean densities of ≥ 10 mm prey species for habitats sampled in each Lauderdale survey zone (Habitats: S = unvegetated sand, G = seagrass, R = sand interspersed with rocks, P = sand interspersed with pebbles, D = dense rocky rubble).

75 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Stress: 0.16 Spring 2006

Summer 2007 Stress: 0.13 1N1 2N1

3N1 4N1

1N2 2N2

3N2 4N2

1S 2S

Stress: 0.14 Winter 2007

Figure 36 MDS plots of mean densities of ≥ 10 mm prey species at different tide heights in each Lauderdale survey zone (Tide height categories: 1 = highest on the shore; through to 4 = lowest on the shore).

76 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 19 Mean sizes (mm) of prey species for tidal height categories at Lauderdale based on individuals ≥ 10 mm in combined grid and non-grid samples (category 1 = highest on shore, category 4 = lowest; refer to Figure 31).

Spring 2006 - Species 1 2 3 4 Anapella cycladea 20.1 24.7 35 N/A Katelysia scalarina 27 24.9 21.2 18.5 Bivalves – Other 18.1 35.6 15.3 12.5 Nephtys australiensis 22.6 19.7 25.3 19.4 Leitoscoloplos normalis 16.7 16.4 14.2 40 Olganereis edmonsi 35.8 16 27 N/A Polychaetes – Other 29.1 12.5 34.2 16.5 Salinator fragilis 12 10.9 N/A N/A

Summer 2007 - Species 1 2 3 4 Anapella cycladea 19.5 23.6 N/A N/A Katelysia scalarina 15.2 14.6 16.7 15.2 Bivalves – Other 32.3 26.5 14.2 14.5 Nephtys australiensis 20.3 16 11.9 14.4 Leitoscoloplos normalis 13.7 22 N/A N/A Olganereis edmonsi 27.1 34 65 75 Polychaetes – Other 46 N/A 16 50 Salinator fragilis 12.1 N/A N/A N/A

Winter 2007 - Species 1 2 3 4 Anapella cycladea 19.5 23.1 N/A N/A Katelysia scalarina 17 18.6 19 N/A Bivalves – Other 17 26.1 23.8 N/A Nephtys australiensis 22 20 22 17 Leitoscoloplos normalis 27 10 N/A N/A Olganereis edmonsi 51 70 89 132 Polychaetes – Other 22 30 49 19 Salinator fragilis 11.7 N/A N/A N/A

The dataset for ≥ 10 mm animals collected at grid survey sites in the three Lauderdale survey zones were further assessed to document size frequency distributions within the size range consumed by birds. Size frequency histograms are presented in Figure 37 to Figure 43 for each of the bivalves Anapella cycladea and Katelysia scalarina, the polychaetes Nephtys australiensis, Leitoscoloplos normalis and Olganereis edmonsi, and for all other bivalves pooled and all other polychaetes pooled. Separate histograms were not prepared for Salinator fragilis, or for other individual less common bivalves, as described in Section 4.2.1. Table 20 indicates mean size for each of the above species and pooled groups in each survey zone to further facilitate comparisons of available prey sizes. Data from non-grid sites was incorporated in the table calculations to maximise sample sizes for estimates of mean sizes in each survey zone. Sample sizes were not uniform between survey zones, as indicated in the size frequency histogram figures, and hence comparisons should be based on relative contributions of size classes rather than total counts in size classes.

Anapella cycladea exhibited similar size distributions at N1 and N2, with the 20-24 mm size class dominating, whilst animals in S demonstrated a different recruitment cycle (Figure 37). Consistent with this, A. cycladea was typically smaller in S than in the two northern zones (Table 20). Katelysia scalarina also exhibited similar size distribution patterns at N1 and N2, although relative seasonal contributions varied in the dominant size classes

77 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

(Figure 38). Prior to winter, the population at S was missing one of the dominant size classes found in the northern zones (15-19 mm) and hence achieved a higher mean size (Table 20). However, given the relatively small sample sizes for this species and the seasonal variation observed, no clear trend can be established for variation in size amongst the survey zones.

The graphs for pooled other bivalves reflect the differentiation of bivalve assemblages in the south versus the north, with a contrasting size frequency distribution in survey zone S (Figure 39). This zone recorded a higher density of the bivalve Tellina deltoidalis, which contributed to the spike in numbers around the 35-39 mm size category that was not detected in the samples from the northern zones. This species typically occurred in high densities in the narrow ‘neck’ section of zone S (= Zone S1, Harrison 2008), within the area categorised as Lauderdale Patch 4 for the Pied Oystercatcher carrying capacity model (Figure 15f).

Higher densities of the mollusc Wallucina assimilis were recorded in S than in the northern zones in some seasons, primarily at the very southern end of the sandflat (i.e. Lauderdale Zone 5 in accordance with Figure 15f), although the majority were < 10 mm and therefore excluded from analyses. Bivalve species such as Soletellina biradiata, Eumarcia fumigata and Paphies erycinea occurred in relatively low numbers in samples, but were identified primarily in the two northern zones. There was no seasonally consistent pattern in size variation with survey zones (Table 20), an unsurprising result given that the pooled species are likely to have varying growth and recruitment patterns.

Nephtys australiensis was the most common polychaete in all survey zones and demonstrated similar size frequency distributions at N1 and N2, with the exception of the absence of occasional large individuals (> 30 mm) in spring and summer at N2 (Figure 40). This species recorded elevated densities in winter in both northern zones, suggesting high levels of recruitment during the latter part of the survey program. As described for Anapella cycladea, zone S seemed to comprise a separate sub-population with contrasting patterns of recruitment and growth. The very low densities of N. australiensis in small size classes in winter indicated that the recruitment event detected in the north had not occurred at the southern end of the sandflat. Larger mean sizes in S in summer and winter were therefore associated with low levels of recent recruitment (Table 20), rather than reflecting a higher occurrence of large individuals, although the largest maximum size was recorded in this zone.

Size frequencies for Leitoscoloplos normalis were relatively uniform across the three survey zones, with the two smallest 5 mm size classes dominating (Figure 41). Also consistent for the three survey zones was the recruitment of animals into the size range consumed by waders in spring, but with little subsequent evidence of recruitment in summer or winter. Mean size of this species was relatively uniform across the three survey zones (Table 20). However, patterns in the size distribution of Olganereis edmonsi were more like those for Nephtys australiensis, with elevated densities and recruitment into available prey size in winter in the northern zones N1 and N2 (Figure 42). While small numbers of large individuals were recorded in winter at Zone S, very few occurred in the smaller wader prey size classes. Animals ≥ 10 mm length occurred in consistently low densities in spring and summer in all three survey zones, during which time few individuals were recorded above 50 mm length. The size frequency distributions suggest that the recruitment event that caused elevated densities in winter at the northern end of the sandflat may have occurred earlier in N2 than N1, or else animals at N2 exhibited faster growth rates. This is revealed by the spike of animals around 90 mm size and the lower density of animals in the 10-60 mm range at N2. The maximum size recorded for O. edmonsi was a 208 mm individual at N1 in winter, representing the largest polychaete observed during the entire survey program. Mean sizes also suggest that this species was the largest polychaete species present on the sandflat, although this was most obvious when the species became abundant in winter (Table 20).

78 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale N1 250

200

n = 17 (s) 150 n = 30 (w)

100 Frequency

50

0 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm)

250

250 Spring 2006 200 Lauderdale N2 200 15 0 10 0 50 Summer 2007 n = 14 (s) 0 10 - 15 - 20- 25- 30- 35-

150 n = 28 (w) 14 Winter19 24 29 200734 39

100 Frequency 50

0 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm)

250

200 Lauderdale S

150

n = 9 (s) 100

Frequency n = 23 (w)

50

0 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm)

Figure 37 Size frequency histograms for the bivalve Anapella cycladea in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w).

79 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale N1 35

30

25

20 n = 17 (s) n = 30 (w) 15 Frequency 10

5

0 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm)

Lauderdale N2 35

30 250 Spring 2006 200 15 0 10 0 25 50 Summer 2007 n = 14 (s) 0 10 - 15 - 20- 25- 30- 35- 20 n = 28 (w) 14 Winter19 24 29 200734 39

15 Frequency 10

5

0 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm)

Lauderdale S 35

30

25

20 n = 9 (s) n = 23 (w) 15 Frequency 10

5

0 10-14 15-19 20-24 25-29 30-34 35-39 Size class (mm)

Figure 38 Size frequency histograms for the bivalve Katelysia scalarina in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w).

80 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale N1 6

5

4

3 n = 17 (s) n = 30 (w) Frequency 2

1

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm)

Lauderdale N2 6

250 Spring 2006 5 200 15 0 10 0 50 Summer 2007 n = 14 (s) 0 4 10 - 15 - 20- 25- 30- 35- n = 28 (w) 14 Winter19 24 29 200734 39 3

Frequency 2

1

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm)

Lauderdale S 6

5 n = 9 (s) 4 n = 23 (w)

3

Frequency 2

1

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm)

Figure 39 Size frequency histograms for the other bivalve species (pooled) in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w).

81 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale N1 80 70 60 50 40 n = 17 (s) n = 30 (w) Frequency 30 20 10 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 Size class (mm)

Lauderdale N2 80 70 250 Spring 2006 200 15 0 60 10 0 50 Summer 2007 n = 14 (s) 0 50 10 - 15 - 20- 25- 30- 35- n = 28 (w) 14 Winter19 24 29 200734 39 40

Frequency 30 20 10 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 Size class (mm)

Lauderdale S 80 70 60 50 40 n = 9 (s) n = 23 (w)

Frequency 30 20 10 0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 Size class (mm)

Figure 40 Size frequency histograms for the polychaete Nephtys australiensis in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w).

82 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale N1 30

25

20 n = 17 (s) 15 n = 30 (w)

Frequency 10

5

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm)

Lauderdale N2 30

250 Spring 2006 200 15 0 25 10 0 50 Summer 2007 n = 14 (s) 0 10 - 15 - 20- 25- 30- 35- 20 n = 28 (w) 14 Winter19 24 29 200734 39

15

Frequency 10

5

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm)

Lauderdale S 30

25

20

15 n = 9 (s)

Frequency 10 n = 23 (w)

5

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 Size class (mm)

Figure 41 Size frequency histograms for the polychaete Leitoscoloplos normalis in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w).

83 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale N1 6

5

4 n = 17 (s) 3 n = 30 (w)

Frequency 2

1

0 10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 100-104 110-114 120-124 130-134 140-144 150-154 160-164 170-174 180-184 190-194 200-204 Size class (mm)

Lauderdale N2 6 250 Spring 2006 200 15 0 10 0 50 Summer 2007 5 n = 14 (s) 0 10 - 15 - 20- 25- 30- 35- 4 n = 28 (w) 14 Winter19 24 29 200734 39

3

Frequency 2

1

0 10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 100-104 110-114 120-124 130-134 140-144 150-154 160-164 170-174 180-184 190-194 200-204 Size class (mm)

Lauderdale S 6

5

4 n = 9 (s) 3 n = 23 (w)

Frequency 2

1

0 10-14 20-24 30-34 40-44 50-54 60-64 70-74 80-84 90-94 100-104 110-114 120-124 130-134 140-144 150-154 160-164 170-174 180-184 190-194 200-204 Size class (mm)

Figure 42 Size frequency histograms for the polychaete Olganereis edmonsi in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w).

84 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale N1 5

4

3 n = 17 (s) 2 n = 30 (w) Frequency

1

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99

Size class (mm)

Lauderdale N2 250 Spring 2006 5 200 15 0 10 0 50 Summer 2007 n = 14 (s) 0 4 10 - 15 - 20- 25- 30- 35- n = 28 (w) 14 Winter19 24 29 200734 39 3

2 Frequency

1

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99

Size class (mm)

Lauderdale S 5

4

3 n = 9 (s) 2 n = 23 (w) Frequency

1

0 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99

Size class (mm)

Figure 43 Size frequency histograms for the other polychaete species (pooled) in each Lauderdale survey zone, with data provided for the three seasons surveyed. n = number of core samples collected in spring/summer (s) and winter (w).

85 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

As described above for the pooled bivalve group, comparisons of sizes for the pooled polychaete group are complicated by variable species compositions and associated life history attributes. The size frequency distributions demonstrated variation amongst the three survey zones, with spikes of smaller size classes in spring at N1 and to a lesser extent S, and in winter at N2. The species contributing to elevated densities of other polychaetes at N1 in spring included Magelona sp, Phyllodoce sp. and Gonianid sp., while the spike in the 10-14 mm size class in winter at N2 was caused by a range of species including Australonereis ehlersi, Euzonus sp. and Phyllodoce sp. The largest polychaete recorded in the pooled group was A. ehlersi, which accounted for the large individuals recorded during spring at N2. In survey zone S, the slightly increased numbers in spring consisted of Abarenicola affinis and Lumbrinerid sp. Mean sizes for the pooled polychaete group varied substantially amongst survey zones in spring and summer, whilst being uniform in winter. There was no clear trend for these species to attain larger sizes in any one survey zone.

Table 20 Mean sizes (mm) of prey species in Lauderdale survey zones based on individuals ≥ 10 mm in combined grid and non-grid samples.

Spring 2006 - Species Taxonomic Group N1 N2 S Anapella cycladea Bivalvia (Mollusca) 20.5 21.1 19.4 Katelysia scalarina Bivalvia (Mollusca) 23.1 21.8 26.2 Bivalves – Other Bivalvia (Mollusca) 21.3 13 25.3 Nephtys australiensis Polychaete (Annelida) 24.6 17.1 22.6 Leitoscoloplos normalis Polychaete (Annelida) 18 14 16.2 Olganereis edmonsi Polychaete (Annelida) 23.5 N/A 41 Polychaetes – Other Polychaete (Annelida) 19.1 47 17.8 Salinator fragilis Gastropoda (Mollusca) 11.6 11.2 12.5

Summer 2007 - Species Taxonomic Group N1 N2 S Anapella cycladea Bivalvia (Mollusca) 20.7 21.1 17.8 Katelysia scalarina Bivalvia (Mollusca) 15 15.3 16 Bivalves – Other Bivalvia (Mollusca) 37.2 17.2 34 Nephtys australiensis Polychaete (Annelida) 15.1 12.1 26.9 Leitoscoloplos normalis Polychaete (Annelida) 18 N/A 15 Olganereis edmonsi Polychaete (Annelida) 31.2 37.5 33.2 Polychaetes – Other Polychaete (Annelida) 33.5 N/A 58 Salinator fragilis Gastropoda (Mollusca) 11.2 11.2 12.8

Winter 2007 - Species Taxonomic Group N1 N2 S Anapella cycladea Bivalvia (Mollusca) 21 21 17.7 Katelysia scalarina Bivalvia (Mollusca) 17.3 19.8 17.1 Bivalves – Other Bivalvia (Mollusca) 23.7 21.5 25.2 Nephtys australiensis Polychaete (Annelida) 19 20 43 Leitoscoloplos normalis Polychaete (Annelida) 21 28 31 Olganereis edmonsi Polychaete (Annelida) 55 76 77 Polychaetes – Other Polychaete (Annelida) 26 33 27 Salinator fragilis Gastropoda (Mollusca) 10.2 10.8 11.9

86 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

While Section 4.2.1 provides an overview of sediment types at Lauderdale, the same dataset was further assessed to compare the survey zones N1, N2 and S. As described in Section 4.2.1, these data have also been described and included in raw format in the estuarine and marine ecology technical report (Aquenal 2008b) and the raw data are not repeated here.

No coarse material (>2 mm diameter) was recorded at any of the S sites, while most northern sites had small quantities of coarse material (average 4% in N1 and N2) (Figure 44). Volumes of coarse sand (2->0.5 mm) were low, while fine-medium sand (0.5-> 0.063 mm) formed the majority of sediment in all survey zones, although one site in N1 near the shoreline had fairly equal volumes of fine-medium sands and finer silt/clay material. In S, volumes of fine-medium sands were consistently in the 92-94% range, while they were more variable in N1 (46 to 100%) and N2 (74 to 97%). In the case of fines (<0.063 mm), volumes were low throughout in all areas, with the exception of the one N1 site mentioned above. In S, values were consistently 6-8%, while they were again more variable in N1 (0-47%) and N2 (0 to 11%).

Overall, the north zones provide slightly coarser and more variable sedimentary habitats that the south, where sediment profiles demonstrate very consistent particle size distributions (Figure 44). The dominance of sands and generally low levels of fines across all survey zones reflect the moderate levels of water movement resulting from regular tidal flushing. While S is most protected from wind and wave effects, it did not have substantially higher levels of fines than the northern zones on the basis of analyses presented here. However some more detailed particle size analyses of a small number of samples from the Lauderdale sandflats (see Technical Advice on Water 2007) revealed smaller percentile sediment sizes at the very southern end compared with the north, with the exception of some northern sites located very close to shore that may have been influenced by stormwater inputs. This suggests that sediments at the southern end are finer than in the more wind and wave exposed northern area of sandflat.

Redox potential profiles were similar in the three survey zones, with values of ~ 300-500 mV at 1 cm depth, reduced but mostly positive values at 4 cm depth and negative values in most samples at 10 cm depth (Figure 45). This is consistent with observations of black streaks in deeper sections of cores, reflecting anoxic conditions.

Subtle differences in particle size between the northern (N1 and N2) and southern (S) areas of the sandflat may help to explain some of the differences in prey species densities observed between these areas. On the basis of animals within the size range consumed by waders (≥10 mm length), the southern zone recorded higher densities and smaller sizes of the bivalve Anapella cycladea, higher densities of the gastropod Salinator fragilis and lower densities of the bivalve Katelysia scalarina. It also recorded reduced densities of polychaetes at certain times compared with the northern zones. For example, significant recruitment events for Olganereis edmonsi and Nephtys australiensis in N1 and N2, indicated by elevated numbers at the lowest end of the wader prey size range in winter, were not recorded in the southern zone. The southern end of the sandflat differs from the north in terms of wind and wave exposure, tidal elevation, levels of water movement and benthic habitats, such that particle size is only one contributing factor to differences observed in wader prey assemblages.

4.3 EPIBENTHIC FAUNA

Native blue mussels (Mytilus galloprovincialis) and feral Pacific oysters (Crassostrea gigas) were surveyed at Lauderdale, South Arm and Pipeclay Lagoon as described in Sections 3.3.3 and 3.4.2 to collect data on the densities and sizes of these species within observed Pied Oystercatcher foraging zones.

The mean densities of both species in each bay are indicated in Table 21 on the basis of all individuals counted and in Table 22 on the basis of individuals within the size range consumed by Pied Oystercatchers. The tables present

87 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

L1 100 N1 L3 L5 80 L7 L9 60 L11 L13 L14 40 L16

20 Cumulative volume (%)

0 2 0.5 0.063 <0.063 Particle size (mm)

100 N2 L19 80 L21 L22 60 L24 L27 L29 40 L30

20 Cumulative volume (%) 0 2 0.5 0.063 <0.063 Particle size (mm)

100 S

80 L33 L35 L37 60 L39 40

20 Cumulative volume (%) 0 2 0.5 0.063 <0.063 Particle size (mm)

Figure 44 Particle size distributions in intertidal core samples from sites in survey zones N1, N2 and S at Lauderdale.

88 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

600

500 N1 400 L1 L3 300 L5 200 L7 L9 100 L11 0 L13 Redox Potential (mV) 1 4 10 L14 -100 L16 -200

-300 Depth (cm)

600 500 N2 400

300 L19 200 L21 100 L22 0 L24 1 4 10 L27 -100

Redox Potential (mV) L29 -200 L30 -300 -400 -500 Depth (cm)

500

400 S 300

200 L33 100 L35 0 L37 1410L39 -100 Redox Potential(mV) -200

-300

-400 Depth (cm)

Figure 45 Redox potential values at sediment depths of 1 cm, 4 cm and ~10 cm (or greatest depth possible to a maximum of 10 cm) in intertidal core samples from sites in survey zones N1, N2 and S at Lauderdale.

89 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

density data for 5 m transect interval categories, averaged across transects, as well as mean density values across all transect interval categories. Note that density estimates calculated using the dataset limited to animals within the size range consumed by birds include a smaller number of transect interval categories because animals were not measured in all intervals (see Section 3.4.2).

Based on all animals observed, the mean density of oysters was low (< 1 per m2) at Lauderdale and South Arm, whilst comparatively high (> 5 per m2) at Pipeclay Lagoon. In contrast, densities of mussels were fairly uniform across the three bays, ranging from 1.2 to 1.8 per m2 (Table 21). It should be noted that the oyster/mussel foraging zone mapped at Pipeclay Lagoon on the basis of wader foraging observations was less than half the size of the zones mapped at Lauderdale and South Arm. When densities are applied to sizes of mussel/oyster beds, population sizes for mussels are therefore likely to be larger at Lauderdale and South Arm than Pipeclay Lagoon, while the population size of oysters is still estimated to be greatest at the latter location.

Harrison (2008) observed birds feeding on individuals 30-69 mm in the case of Crassostrea gigas and 23-82 mm for Mytilus galloprovincialis. To align with the 5 mm size classes incorporated in the carrying capacity model for the Pied Oystercatcher, the size range of M. galloprovincialis considered to comprise ‘available’ prey was adjusted slightly to 20-85 mm. When the density data were re-analysed just including animals within the prey size ranges observed by Harrison (2008), results for oysters were very different to those for animals of all sizes. Densities were very low at Lauderdale and Pipeclay Lagoon (< 0.1 per m2), and also low at South Arm (0.17 per m2) (Table 22). The densities indicate that a large portion of total animals observed at South Arm were within the range consumed by birds, whilst the majority of animals at Lauderdale and Pipeclay Lagoon were not. They also indicate that, at the respective time of the surveys, the largest total numbers of oyster prey were at South Arm on the basis of densities of suitable oysters as well as the size of the oyster bed. In contrast to oysters, densities of mussels within the size range consumed by birds depicted similar results to those for all individuals, with relatively uniform densities across bays, since a fairly high proportion of total animals occurred within the size range consumed by the birds. As indicated above, based on total area of the mussel bed in each bay, it is likely that the highest population sizes occur at Lauderdale and South Arm.

The variation in densities documented above is better understood by examining size frequency histograms for each bay, with results presented in Figure 46 for Crassostrea gigas and Figure 47 for Mytilus galloprovincialis. Sample sizes varied amongst bays, as indicated on the figures, and hence comparisons should be based on relative contributions of size classes rather than total counts for size classes. Size frequencies of C. gigas indicate that the majority of the oysters present at Lauderdale and Pipeclay Lagoon were larger than the size range observed as prey for Pied Oystercatchers (Figure 46). This is likely to be a limiting factor in terms of the birds utilising oysters as a food source. In contrast, at the time of surveying, a large portion of oysters measured at South Arm were within the size range consumed. It should be noted that, as described in Sections 3.1 and 3.3.3, epibenthic surveys at Lauderdale and Pipeclay Lagoon were conducted in July 2007 while the survey of South Arm was delayed until May 2008. It is therefore not possible to determine if the differences in patterns of recruitment between South Arm and the other two bays are due to location differences or interannual/seasonal variation. However if size distributions had been similar in all bays during winter 2007, a fairly major die-back event would have been required to explain the subsequent loss of animals > 70 mm at South Arm. Based on this, and observations of bird survey field staff who reported ‘low densities of oysters at South Arm’ during 2007, it is likely that there are typically less large and visually conspicuous oysters in that bay. Pipeclay Lagoon and Lauderdale had similar size frequency distributions, with highest numbers recorded in the 110-155 mm size range, although there was more evidence of recent recruitment at Lauderdale than at Pipeclay Lagoon. In contrast, the highest numbers at South Arm were recorded in the 35-70 mm range, coinciding almost exactly with the size range consumed by Pied Oystercatchers.

90 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 21 Mean densities of oysters and mussels based on animals of all sizes.

OYSTERS Lauderdale Pipeclay Lagoon South Arm Mean Mean Mean Transect interval count Density per m2 count Density per m2 count Density per m2 0-5 m 21.20 1.41 5.75 0.38 7.25 0.48 10-15 m 21.00 1.40 220.00 14.67 6.13 0.41 20-25 m 18.60 1.24 88.25 5.88 4.38 0.29 30-35 m 11.00 0.73 127.33 8.49 2.71 0.18 40-45 m 8.75 0.58 26.00 1.73 2.80 0.19 50-55 m 7.75 0.52 4.00 0.27 3.75 0.25 60-65 m 3.50 0.23 2.00 0.13 70-75 m 2.00 0.13 2.00 0.13 TOTAL 11.73 0.78 78.56 5.24 3.88 0.26

MUSSELS Lauderdale Pipeclay Lagoon South Arm Transect interval Mean Density per m2 Mean Density per m2 Mean Density per m2 0-5 m 49.60 3.31 1.00 0.07 23.50 1.57 10-15 m 47.40 3.16 19.00 1.27 23.88 1.59 20-25 m 37.00 2.47 25.75 1.72 23.50 1.57 30-35 m 20.50 1.37 54.67 3.64 19.86 1.32 40-45 m 9.50 0.63 45.00 3.00 14.40 0.96 50-55 m 14.25 0.95 19.00 1.27 15.75 1.05 60-65 m 3.00 0.20 15.00 1.00 70-75 m 12.50 0.83 8.00 0.53 TOTAL 24.22 1.61 27.40 1.83 17.99 1.20

Table 22 Mean densities of oysters and mussels based on animals within the size range consumed by Pied Oystercatchers.

OYSTERS Lauderdale Pipeclay Lagoon South Arm Transect interval Mean Density per m2 Mean Density per m2 Mean Density per m2 10-15 m 1.00 0.067 0.25 0.017 4.63 0.308 30-35 m 2.75 0.183 0.33 0.022 1.29 0.086 50-55 m 1.00 0.067 1.00 0.067 2.25 0.150 70-75 m 0 0 2.00 0.133 TOTAL 1.19 0.08 0.53 0.04 2.54 0.17

MUSSELS Lauderdale Pipeclay Lagoon South Arm Transect interval Mean Density per m2 Mean Density per m2 Mean Density per m2 10-15 m 32.60 2.173 3.50 0.233 23.00 1.533 30-35 m 17.00 1.133 24.00 1.600 19.57 1.305 50-55 m 11.50 0.767 20.00 1.333 15.00 1.000 70-75 m 12.00 0.800 7.50 0.500 TOTAL 18.28 1.22 15.83 1.06 16.27 1.08

91 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

The size frequency plots for the three bays were more uniform in the case of the mussel Mytilus galloprovincialis despite the variation in survey times described above. The majority of the mussels found in the survey areas werewithin the size range consumed by Pied Oystercatchers (Figure 47). This suggests that the mussels may provide a more reliable foraging resource, with a large percentage of animals available as prey due to their suitable size. This cannot be confirmed in the absence of longer term datasets that assess seasonal and annual variation in densities and size frequency distributions, however it is consistent with the Pied Oystercatchers feeding more frequently on mussels than on oysters during the foraging ecology surveys (Harrison pers. comm.).

Despite different survey periods, the size frequency distributions for mussels were similar at Pipeclay Lagoon and South Arm, with numbers peaking in the 60-75 mm range, although evidence of a recent recruitment event at Pipeclay Lagoon was virtually absent at South Arm. The higher counts at the latter bay at least partially represent a sampling artefact since the oyster/mussel foraging zone and corresponding sample size were larger at South Arm. Lauderdale also recorded recent recruitment, perhaps indicative of being surveyed at the same time as Pipeclay Lagoon, but was dominated by animals in smaller size classes than those in the other two bays. This depicts inter- bay variation in recruitment and/or growth patterns separate to seasonal or other temporal effects.

Mean sizes of measured oysters and mussels in each bay are indicated in Table 23. When calculations were based on all animals observed, the mean size of oysters was highest at Pipeclay Lagoon closely followed by Lauderdale, while South Arm oysters were considerably smaller. Sizes of mussels were more uniform, consistent with size frequency distributions, although there was a trend for larger sizes at South Arm and Pipeclay Lagoon. On the basis of animals within the size range consumed by Pied Oystercatchers, the mean size of oysters was highest at Pipeclay Lagoon, however South Arm oysters were comparable sizes to those at Lauderdale. Results for mussels were similar to those based on all individuals, with highest mean sizes at South Arm and Pipeclay Lagoon.

Overall the results indicate that oysters within the dietary size range of the Pied Oystercatcher occurred at higher densities at South Arm than at Lauderdale and Pipeclay Lagoon, whilst being of similar size to those at Lauderdale but slightly smaller than at Pipeclay Lagoon. Densities of suitably sized oysters were low in all bays. Densities of suitably sized mussels were much higher; 15 fold at Lauderdale, 30 fold at Pipeclay and six fold at South Arm compared with oysters. Mussels occurred at slightly higher densities, but were smaller on average, at Lauderdale compared with the other two bays. The size of the mussel/oyster bed is also important in understanding the total size of the prey resource, with the larger beds identified at South Arm and Lauderdale combined with the above results suggesting a considerably larger oyster population at South Arm and larger mussel populations at South Arm and Lauderdale compared with Pipeclay Lagoon. The role of different sampling periods in contrasting results for oysters at South Arm remains unclear, while human activities may affect the densities of oysters in Pipeclay Lagoon due to a regular clean-up program coordinated by the shellfish industry. This program is aimed at removing feral oysters since they are categorised as an introduced pest in Australia. It is likely that these activities are focussed more on public access areas rather than the wader foraging ground surveyed in the current study, however removal of oysters elsewhere is likely to influence recruitment levels across the wider lagoon.

92 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale 30

25 n = 15 20 y

15

Frequenc 10

5

0 15-19 25-29 35-39 45-49 55-59 65-69 75-79 85-89 95-99 105-109 115-119 125-129 135-139 145-149 155-159 165-169 175-179 185-189 195-199 205-209 215-219 Size class (mm)

Pipeclay Lagoon 30

25 n = 8

y 20

15

Frequenc 10

5

0 15-19 25-29 35-39 45-49 55-59 65-69 75-79 85-89 95-99 105-109 115-119 125-129 135-139 145-149 155-159 165-169 175-179 185-189 195-199 205-209 215-219 Size class (mm)

South Arm 30 Key Below prey size 25 n = 21 Wader prey

y 20 Exceed prey size 15

Frequenc 10

5

0 15-19 25-29 35-39 45-49 55-59 65-69 75-79 85-89 95-99 105-109 115-119 125-129 135-139 145-149 155-159 165-169 175-179 185-189 195-199 205-209 215-219 Size class (mm)

Figure 46 Size frequency histograms for the Pacific oyster Crassostrea gigas in each bay surveyed indicating the size classes within the prey size range of Pied Oystercatchers (‘Wader prey’). n = number of 5 m transect intervals surveyed.

93 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Lauderdale 80 70 60 n = 15

y 50 40

Frequenc 30 20 10 0 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99

Size class (mm)

Key Pipeclay Lagoon 80 Below prey size 70 Wader prey

60 n = 8 Exceed prey size

y 50 40

Frequenc 30 20 10 0 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99

Size class (mm)

South Arm 80 70 60 n = 21

y 50 40

Frequenc 30 20 10 0 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99

Size class (mm)

Figure 47 Size frequency histograms for the native blue mussel Mytilus galloprovincialis in each bay surveyed indicating the size classes within the prey size range of Pied Oystercatchers (‘Wader prey’). n = number of 5 m transect intervals surveyed.

94 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Table 23 Mean sizes of oysters and mussels based on all animals observed and animals within the dietary size range of the Pied Oystercatcher.

All animals

Bay Oysters Mussels Length (mm) n Length (mm) n Lauderdale 112.5 171 38.9 339 Pipeclay Lagoon 130.1 280 51.0 132 South Arm 64.5 87 61.6 409

Animals in the dietary size range of the Pied Oystercatcher

Bay Oysters Mussels Length (mm) n Length (mm) n Lauderdale 53.4 20 41.9 301 Pipeclay Lagoon 61.3 3 59.7 106 South Arm 52.9 59 61.6 396

5 SUMMARY AND DISCUSSION

An invertebrate sampling program was conducted to collect data on wader prey species at Lauderdale and in surrounding bays that may have links to the proposed Lauderdale Quay development zone. The bays surveyed included Mortimer Bay, South Arm, Pipeclay Lagoon, Five Mile Beach, Barilla Bay and Orielton Lagoon in addition to Lauderdale. Sampling was primarily designed to collect data required for a Pied Oystercatcher carrying capacity model (Atkinson and Stillman 2008), but also to provide data on prey species for other important waders identified in bird utilisation and foraging ecology surveys (Aquenal 2008a, Harrison 2008).

Through the foraging study of Harrison (2008) and examination of invertebrate samples collected here, it was determined that the ‘main prey’ species for the Pied Oystercatcher are the bivalves Anapella cycladea and Katelysia scalarina; and polychaetes Nephtys australiensis, Leitoscoloplos normalis and Olganereis edmonsi. The gastropod Salinator fragilis and epibenthic bivalves Mytilus galloprovincialis and Crassostrea gigas were identified as additional dietary items and have also been categorised as ‘main prey’ for the purpose of the invertebrate analyses. Bivalves and polychaetes were widespread as prey across the study area, while S. fragilis, M. galloprovincialis and C. gigas were identified to be important prey in a subset of the bays surveyed, including Lauderdale (Harrison 2008). The above species as well as less common benthic infauna bivalves and polychaetes contributed 98% of observed Pied Oystercatcher dietary items and were the species analysed in the current report and included as input for the carrying capacity model. Data collected related to their densities (abundance per sample), sizes and Ash Free Dry Masses (AFDMs), although analysis of the latter is included in the modelling report (Atkinson and Stillman 2008) and not presented here. Additional analysis was included for the density of the crabs Paragrapsus gaimardii and Mictyris platycheles which, together with the above species, contributed 75% of prey items for other waders.

Benthic infauna were surveyed using core samples from sites distributed using a grid design, consistent with sampling designs used elsewhere for similar carrying capacity modelling studies, with some additional sites sampled at Lauderdale to target particular habitats or facilitate comparisons between the northern proposed development zone and the southern sandflat. Benthic infauna were sampled during three seasons – spring, summer and winter – to

95 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay coincide with key aspects of the lifecycles of important wader species. Epibenthic mussels and oysters were sampled using a similar system based on evenly spaced transects and sample sites, however seasonal data are not available for these species due to their late identification as prey in a small number of areas. Data were also collected for physico-chemical sediment parameters (particle size distribution and redox potential) at representative benthic infauna sites, while sites were categorised on the basis of level of tidal inundation using tide height data collected to assess foraging habitat exposure for the Pied Oystercatcher carrying capacity model (refer to Atkinson and Stillman 2008). These environmental data were used to assist with the interpretation of the prey data.

The current report primarily describes trends in the distributions, densities and sizes of prey species for Pied Oystercatchers and other waders, and makes no attempt to estimate the total abundance or biomass of available prey resources in each bay or area surveyed. It is instead a descriptive background data report to the Pied Oystercatcher carrying capacity model study, the latter assessing total foraging resources and carrying capacity using the invertebrate density, size and AFDM data collected in the current study, as well as data on sandflat area and exposure, wader ecology and additional environmental variables. For other wader species, information on prey resources is limited primarily to the invertebrate density data presented here and the foraging data presented by Harrison (2008), since applicable carrying capacity models were not identified for these species. However polychaetes comprised a major prey type for both Pied Oystercatchers and many other waders; hence polychaete foraging resource estimates calculated by Atkinson and Stillman (2008) as part of the Pied Oystercatcher model provide information on the biomass distribution of this food source for other waders.

Trends in the invertebrate data are discussed below for comparisons amongst the seven bays surveyed, and amongst three survey zones at Lauderdale: N1 – corresponding to the majority of the proposed development site, N2 – the area to the south of N1 that is still north of the southern narrow channel, and S – the southern part of the sandflat. Two datasets were analysed for the benthic infauna wader prey species: 1) including animals of all sizes; and 2) including animals ≥ 10 mm, deemed to be ‘available’ as food to waders based on foraging observations. Results for the above two datasets were generally very similar, but several important differences were noted due to, for example, high densities of < 10 mm bivalves belonging to Wallucina assimilis at Five Mile Beach, and a considerably higher proportion of ≥ 10 mm polychaetes belonging to Olganereis edmonsi in summer and winter at South Arm. Recruitment patterns will affect availability of prey such as O. edmonsi, which as an adult reaches lengths greatly exceeding 10 mm, while only a small portion of W. assimilis individuals ever exceed 10 mm length and hence many individuals are ‘unavailable’ as prey regardless of recruitment. The results indicate the importance of considering size when sampling the densities of wader prey, and the discussion below focuses on data for prey that are within the ‘available’ size range, except where otherwise specified.

Prey species for the Pied Oystercatcher

Comparisons amongst bays

Across all seasons, the highest density of benthic infauna prey was recorded at Lauderdale, closely followed by Mortimer Bay, when all sizes of individuals were included. When only animals ≥ 10 mm were considered, the highest density was recorded at South Arm, closely followed by Lauderdale and then Mortimer Bay. The higher density at South Arm using ≥ 10 mm animals was due to the larger size of Olganereis edmonsi at this location as referred to above. These three Ralphs Bay locations therefore contained the highest total mean densities of Pied Oystercatcher prey species. Barilla Bay recorded the next highest mean density, while remaining bays recorded considerably lower values. Some seasonal variation was observed, with Lauderdale recording the highest prey densities in spring, South Arm recording the highest densities in summer, and Lauderdale, Mortimer Bay and South Arm all recording similarly elevated densities compared with other bays in winter.

96 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

While the invertebrate data presented here do not represent total biomass of available food, there are nevertheless some broad consistencies between the invertebrate prey densities and Pied Oystercatcher counts (Aquenal 2008a). As with available prey, the highest numbers of oystercatchers were recorded in Ralphs Bay. The largest aggregations occurred specifically at Lauderdale and South Arm, while numbers at Mortimer Bay were reduced but still higher than in most other bays. Lower bird counts at Mortimer Bay may be the result of reduced accessibility of food due to a steeper shore profile, or alternatively are associated with food quality and/or non-foraging resource variables such as disturbance.

For the Pied Oystercatcher prey species, average counts across seasons indicated highest densities of available (≥ 10 mm) bivalves at Lauderdale, followed by Barilla Bay, while densities of polychaetes were highest at South Arm followed by Mortimer Bay, and the gastropod Salinator fragilis reached highest densities at Lauderdale. Prey species were dominated numerically in all seasons by polychaetes at Mortimer Bay, South Arm, Pipeclay Lagoon and Orielton Lagoon, and by bivalves at Lauderdale and Five Mile Beach, while the dominant prey group varied seasonally at Barilla Bay. While bivalves dominated counts at Lauderdale, densities of polychaetes and bivalves were fairly similar at this location during winter and, in particular, spring.

Anapella cycladea was the dominant bivalve for ≥ 10 mm individuals in all bays except Mortimer Bay and South Arm, where Katelysia scalarina was more common. In these two bays, the absence or low density of available A. cycladea in samples may reflect steeper upper shores and hence reduced habitat for this predominantly high-shore species. The density of K. scalarina was still highest at Lauderdale, followed by Mortimer Bay and then South Arm, while ≥ 10 mm A. cycladea was most common at Lauderdale and Barilla Bay, followed by Five Mile Beach. Average densities of the main prey polychaete species Nephtys australiensis, Leitoscoloplos normalis and Olganereis edmonsi across seasons were highest at South Arm or Mortimer Bay. The three Ralphs Bay locations recorded higher densities of N. australiensis than all other bays, whilst the same was true for O. edmonsi except for a higher density at Pipeclay Lagoon than at Lauderdale. Leitoscoloplos normalis was the least common of the three species overall, but recorded highest densities at Five Mile Beach after Mortimer Bay. These results indicate that the highest densities of all individual benthic infauna main prey species were consistently found in one or more of the Ralphs Bay locations, although the bivalve A. cycladea was most common at Lauderdale and reached similarly high densities at Barilla Bay.

Using density and species composition data, multivariate analyses were used to assess patterns of similarity amongst bays in prey species assemblages. These analyses indicated that seasonal variation was small compared with inter- bay variation. Lauderdale occupied a central position in multidimensional scaling (MDS) plots, suggesting that it is ‘intermediate’ with relation to prey assemblage composition across the wider study area. Lauderdale, South Arm, Pipeclay Lagoon and Barilla Bay formed a broad sub-group, reflecting similar assemblages in these bays. Mortimer Bay was dissimilar due to the absence of the bivalve ≥ 10 mm Anapella cycladea from samples, while Five Mile Beach also separated from the above sub-group above due to low densities of the polychaetes Nephtys australiensis and Olganereis edmonsi. Orielton Lagoon was highly dissimilar to all other bays since it consistently recorded the lowest total densities of prey species and had reduced densities of the bivalves A. cycladea and Katelysia scalarina (the latter absent from all ≥ 10 mm samples) and polychaetes O. edmonsi and Leitoscoloplos normalis. The lagoon represents a highly modified system, with tidal flushing limited by causeway construction and water quality influenced by catchment inputs from the Orielton Rivulet, which help to explain the dissimilar prey assemblage. While previous remediation works to increase the size of culverts have improved flushing and environmental health of the lagoon (e.g. Davies et al. 2006), abundances of prey species are still likely to be below natural levels.

Further multivariate analyses using individual sample site data were analysed on the basis of four categories of shore height determined using tidal data. While there was considerable overlap amongst sites sampled at different tidal heights, those from the highest tide level supported higher densities of Anapella cycladea and Salinator fragilis, while the polychaete Nephtys australiensis tended to occur at higher densities at the lowest tide level. This suggests

97 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay that some species are not evenly dispersed across the tidal gradient, in which case their availability will vary depending on tidal state.

In addition to the above assessments of prey density and community composition, data on size of prey were examined for each bay. Mean size was calculated for each main prey species and grouping of less common bivalves and polychaetes, but these values can vary with recruitment patterns and hence size frequency distributions were also assessed. Using the grid data for ≥ 10 mm individuals, the bivalve Anapella cycladea recorded the largest mean size at South Arm, followed by Pipeclay Lagoon, while the lowest mean size at Barilla Bay was the result of a higher level of recent recruitment. While the two former bays were dominated by a larger size class than other areas, they supported relatively low densities of A. cycladea, suggesting that this species comprised a less common but potentially more energetically profitable prey item. Of the sites where A. cycladea was common (Lauderdale, Barilla Bay and Five Mile Beach), the largest mean size was recorded at Lauderdale. Mean size of the bivalve Katelysia scalarina was also greatest overall at South Arm, a site which recorded a relatively high density of this species (highest behind Lauderdale and Mortimer Bay), while the smallest mean size in Ralphs Bay was recorded at Lauderdale. The latter partially reflects a large and more recent recruitment at Lauderdale, however large animals > 30 mm were more abundant per sample at Mortimer Bay and South Arm. Katelysia scalarina reaches larger adult sizes than A. cycladea, with the former species achieving sizes of ~ 40 mm length in some bays, while the latter species did not exceed 30 mm, with the exception of one individual (35 mm).

Mean sizes of polychaete prey species were influenced to a large extent by recruitment patterns and seasonal fluctuations. For example, Nephtys australiensis reached highest densities at the three Ralphs Bay locations due in part to high levels of recent recruitment into the smallest ‘available’ size categories, a finding which also resulted in low mean sizes for these locations. Leitoscoloplos normalis generally recorded reduced mean sizes in spring when it was common and had high recruitment levels, while recording larger mean sizes in subsequent seasons when it was rare and represented by a small number of larger individuals. A large recruitment event resulted in elevated densities of Olganeresi edmonsi at South Arm in summer, but also resulted in a reduced mean size, while a high mean size was recorded the following winter as the population became dominated by smaller numbers of large individuals. In other bays, densities of O. edmonsi were much lower but mean sizes were frequently larger due to reduced recruitment into the smaller ‘available’ size categories. These results indicate the importance of considering both density and size data when estimating the extent of the available foraging resource. Note that the more detailed analysis of data for Lauderdale (see below) also examined trends in size with relation to level of tidal inundation. This analysis was limited to Lauderdale, since a larger number of sites at various tidal heights were examined at this location and hence it provides the best assessment of whether prey size and tidal height may be related.

No detailed analysis of the relationship between benthic infauna wader prey and sediment characteristics was performed, since broad sediment indicators showed a high level of similarity across all bays except Orielton Lagoon. Bays were dominated by fine-medium sands, with low levels of coarse material, coarse sand and fine silt/clay material. However sediments at Orielton Lagoon were finer, with a larger portion of silt/clay (24%) than in other bays (0-7%). These finer sediments are likely to be due to reduced water movement and particulate inputs from the catchment, as described above, and contribute to the dissimilar prey communities recorded in the lagoon. There were subtle differences amongst locations in Ralphs Bay, with a higher level of coarse material at Lauderdale due to rubble at the northern end and an absence of fines at Mortimer Bay that may be due to greater exposure to prevailing winds and hence wind/wave disturbance. However, on the basis of data for all bays, there was no evident link between these minor differences in sediment profile and densities of the main prey species. The same is true of redox potential; most values were positive at depths of 1 and 4 cm, however negative median values at 10 cm depth in all bays are indicative of anoxic conditions and reflect the relatively sheltered conditions of sandflat habitats.

Surveys of epibenthic oysters Crassostrea gigas and mussels Mytilus galloprovincialis were conducted at Lauderdale (north), South Arm and Pipeclay Lagoon (north), the primary areas where these species were identified

98 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay as prey for Pied Oystercatchers (Harrison 2008). Species-specific minimum and maximum sizes of ‘available’ prey were determined for these species based on foraging observations, with C. gigas growing to a larger size (maximum 220 mm) than M. galloprovincialis (maximum 100 mm) and including a larger portion of individuals deemed too large to be available to birds. Surveys found that densities of available oysters were low in all three bays, but particularly at Lauderdale and Pipeclay Lagoon (<0.1 per m2). Densities of available mussels were similar in all three bays and consistently ~ 1 per m2, with the available prey individuals comprising a large portion of the total population. The mean size of available oysters was highest at Pipeclay Lagoon, while for mussels it was shared between South Arm and Pipeclay Lagoon. The size of the oyster/mussel bed is also important in understanding the total extent of the prey resource, with the bed at Pipeclay Lagoon less than half the size of the beds mapped at Lauderdale and at South Arm. While survey timing differed between the bays and no seasonal data are available, the results suggest that the mussels may provide a more reliable foraging resource than oysters, consistent with slightly higher uptake rates for mussels (Harrison pers. comm.). Of the three bays assessed, the prey density and bed areas suggest that total numerical availability of oysters/mussels may be greatest at South Arm, although their availability at that location may be more tidally limited due to a steeper shore profile. This is indicated by the findings of Harrison (2008) who reported concurrent higher tides and absence of feeding on oysters and mussels at South Arm during winter, whilst feeding on these prey continued at the other two locations.

The proportional contributions of prey types to the total prey assemblage in invertebrate samples (current study) can be compared with data on proportional contributions of these prey types to the diet (Harrison 2008) to assess whether the birds exhibit prey selectivity or forage in accordance with availability. The foraging and invertebrate surveys were conducted concurrently in winter 2007, but sampled in different years for the spring and summer surveys. For the latter seasons, inter-annual variation in prey availability may also affect uptake rates by birds, although it is notable that most of the differences observed between availability and uptake were as applicable during winter as during the other seasons. For example, the bivalve Katelysia scalarina reached higher densities at Lauderdale and Mortimer Bay than in other bays, however it still contributed a small proportion of total available prey items (13-14%) compared with the proportion of consumed items (~40%) during all seasons. This suggests that there may be selectivity for this bivalve on the basis of its larger adult size and therefore energetic profitability (Harrison 2008). To a lesser degree there was also evidence of selectivity for this species in other bays, particularly Barilla Bay and Pipeclay Lagoon.

In contrast, while Anapella cycladea comprised nearly 50% of available prey items at Lauderdale, it only contributed 20% of consumed prey items, with similar findings at Barilla Bay. Elsewhere, predation on this species was relatively consistent with its level of availability, except at Orielton Lagoon where data suggests selectivity for this species and other less common bivalves, possibly due to the virtual absence of Katelysia scalarina. Polychaetes were the preferred prey at South Arm and Pipeclay Lagoon, consistent with them also being the most available prey. They were also the most numerically available prey at Mortimer Bay and Orielton Lagoon, but did not dominate the diet due to preferences for K. scalarina and A. cycladea respectively (see above). Five Mile Beach was the only bay where the overall mean availability of benthic infauna prey items correlated directly with the proportions of consumed items.

The different survey methodology used for epibenthic oysters and mussels prevents direct comparisons of proportional components of available and consumed prey, however it is notable that these species contributed the highest percentage of dietary items at South Arm (Harrison 2008), the bay that also appears to contain the largest combined population numbers. The mussels and oysters provide more food mass per individual than other prey types, however their lower numbers and increased handling time are likely to explain their small numerical contribution to dietary items (0-2%; Harrison 2008). The issue of energetic profitability is discussed by Harrison (2008) and provides a basis for selectivity of certain prey types. The combined invertebrate and dietary data emphasise the need to consider prey density, size, and energetic value when determining the relationship between

99 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay availability and uptake. The carrying capacity model of Atkinson and Stillman (2008) provides the tool for combining these datasets to assess the overall availability of foraging resources.

Comparisons amongst Lauderdale survey zones

Across all seasons, total mean abundance of available (≥ 10 mm) prey in benthic infauna grid samples was highest in the southern zone S, intermediate at N2 and lowest at N1. There was no clear pattern in seasonal variation, with mean prey densities slightly elevated in winter at N1, but depressed at N2 and S. Based on the uniformly dispersed grid sites, the data suggest overall an increase in total densities of available prey from north to south on the Lauderdale sandflat. Inclusion of additional sites targeting rocky habitats at N1 and seagrass habitat at S found that mean prey densities remained highest at S, however values at N1 exceeded those at N2 as a result of increased counts of the bivalve Anapella cycladea. This may be due in part to the rocky habitats being located primarily in the highest shore zone, the tidal habitat preferred by A. cycladea (see below), but also partly due to increased suitability of other environmental conditions. The relatively small area occupied by the rocky habitats (~ 15% of N1) suggests that prey densities based on the grid sites are more representative for the survey zone as a whole, although the increased exposure time for high shore areas indicates a higher contribution to foraging resources relative to shore area occupied.

Pooled data for taxonomic groups of prey species revealed that polychaete and bivalve prey were present in almost equal proportions in N1 grid samples, while there was a decline in the proportional contribution of polychaetes and increase in the contribution of bivalves when moving south through zones N2 and S. The gastropod Salinator fragilis contributed a relatively small percentage of overall prey numbers (3-9%), but also contributed a larger proportion of total prey items towards the southern end of the sandflat. The highest densities of bivalves and the gastropod S. fragilis occurred in zone S in all seasons, with the elevated bivalve counts being primarily responsible for the highest prey densities in S overall (above). Densities of bivalves and S. fragilis were consistently lowest in N1, with the exception of S. fragilis in spring. While the percentage contribution of polychaetes declined from N1 through to S, total mean density of polychaetes was quite similar across all three survey zones in spring and summer, while in winter densities declined at S and remained high at both of the northern zones. The major zonal differences recorded therefore are a higher density of bivalves towards the southern end of the sandflat, and contrasting seasonal shifts in polychaete density between the northern and southern zones.

The species responsible for the north-south gradient in bivalve density at Lauderdale was Anapella cycladea. This was the most abundant bivalve species, and was particularly abundant in the seagrass patch opposite East Marsh Lagoon. Katelysia scalarina was present in lower densities overall, but recorded highest densities in N2 followed by N1, with considerably reduced counts at S. Within S, lower densities were primarily recorded in the southern area opposite East Marsh Lagoon (= Zone S2, Harrison 2008), while counts in the narrower northern section (= Zone S1, Harrison 2008) were more comparable to those in the northern zones. This species therefore did not follow the north-south trend in density demonstrated by A. cycladea. In fact, the total mean density of K. scalarina in spring was highest at N1, whilst being highest at N2 in the other seasons. The next most common bivalve species, Tellina deltoidalis, contributed only a small percentage of total prey items (0.4-3.0%) and followed the same north-south trend in density as A. cycladea, with elevated numbers of large animals recorded in the narrow northern section of Zone S. Size data revealed that mean size of collected A. cycladea was smallest in zone S and comparable in N1 and N2 as a result of variable recruitment between the north and south. There were no clear seasonal or spatial trends in size of K. scalarina, a species that achieved larger maximum sizes than A. cycladea but not larger mean sizes due to higher densities of recent recruits into ‘available’ size categories. Overall, bivalves sampled consisted of more numerous but smaller A. cycladea at the southern end of the sandflat, and more numerous K. scalarina at the northern end.

100 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

The most abundant polychaete at Lauderdale in all survey zones was Nephtys australiensis, although both it and Olganereis edmonsi declined in density towards the southern end. This in conjunction with the elevated numbers of Anapella cycladea explain why the proportional contribution of polychaetes to total mean prey count was reduced in zone S. As found for A. cycladea, N. australiensis demonstrated similar size frequency distributions at N1 and N2, while zone S samples demonstrated contrasting patterns of growth and/or recruitment. Larger mean sizes of N. australiensis at S during summer and winter were primarily due to the absence of the recruitment events observed at N1 and N2. A major recruitment of O. edmonsi also occurred in winter at N1 and N2, but not at S. Overall, data indicate reduced densities of polychaetes at the southern end of the sandflat primarily due to reduced N. australiensis and lower seasonal recruitment of O. edmonsi.

Multivariate analysis incorporating the entire available (≥ 10 mm) benthic infauna prey assemblage at Lauderdale grid sites indicated considerable overlap between N1 and N2, whilst S formed a distinct subgrouping due to the higher densities of Anapella cycladea and Salinator fragilis, and lower densities of Nephtys australiensis and Katelysia scalarina, as described above. Seasonal variation in prey community composition was reduced at S compared with the northern zones, with N1 and N2 demonstrating similar changes with season. The benthic habitat in all areas is dominated by sand, however subtle differences in levels of coarse material and sizes of sand fractions may help to explain the differentiation of S, which is most protected from wind and wave effects. In addition, tidal height data indicate that a very high proportion of zone S occurs in the highest shore category (i.e. lowest level of tidal inundation), the favoured tidal habitat of A. cycladea, compared with N1 and N2. It is notable that targeted sampling of the seagrass habitat specific to zone S found that bivalves (A. cycladea primarily) continued to dominate the prey assemblage, in fact even more so. In contrast, targeted sampling of the rocky habitats specific to N1 recorded a change in dominance, with bivalves numerically dominant over polychaetes, the reverse of findings for the more extensive sand habitats of N1. This reflects a patchier distribution and wider diversity of prey assemblages at N1.

Multivariate analysis of site-level data on the basis of tide height recorded a high level of overlap amongst the three lower shore tide categories across the survey zones, with the highest shore category differentiated on the basis of higher densities of Anapella cycladea, as described for analyses comparing the various bays (see above). This bivalve was generally only found in the two highest tidal categories, and there was a general trend for reduced size in the highest part of its tidal range. Katelysia scalarina and other grouped, less common bivalves were more widely distributed and had more uniform sizes across the tidal gradient. Olganereis edmonsi was only abundant in summer and winter, during which there was a trend for this species to increase in size lower on the shore. The trend for the polychaete Nephtys australiensis to be more abundant at the lowest tide level, noted from the dataset including all bays, was not evident in Lauderdale data. Overall, the analysis of data by tide height at Lauderdale suggests that A. cycladea reaches higher densities higher on the shore, while both this species and the polychaete O. edmonsi are larger on average in the lowest parts of their respective tidal ranges.

Epibenthic mussels and oysters were only surveyed in zone N1 (see section comparing bays, above), since they do not form beds in N2 or S. These larger prey types are therefore only available in N1 and contribute further to the differentiation of prey resources between the northern and southern ends of the Lauderdale sandflat.

Comparisons with foraging data of Harrison (2008) indicate that for the pooled datasets including all seasons, feeding on the bivalve Anapella cycladea was in proportion with its availability at N1 (27-29%) but low (14%) relative to its availability at N2 and S (38-63%). In contrast, the proportion of the diet contributed by Katelysia scalarina (31% at S, 40% at N1, 51% at N2) was much higher than its proportional contribution to invertebrate prey counts (5% at S to 17% at both N1 and N2). Feeding on polychaetes was low at N1 and N2 (~ 20%) compared with availability (36-51%), but high (46%) relative to availability at S (20%). As noted for inter-bay comparisons, inter- annual variation may be a contributing factor in summer and spring comparisons due to timing of surveys, however differences in diet and availability were also detected between the concurrent winter datasets.

101 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Harrison (2008) concluded that Katelysia scalarina, which achieves larger adult sizes than Anapella cycladea, is selected by Pied Oystercatchers on the basis of its higher energetic profitability, with feeding averaged across all seasons being most frequent in the northern zones N1 and N2 and the northern narrow section of zone S (= Zone S1, Harrison 2008) where it was most common. Mussels and oysters are also more profitable than smaller food items and are only available in N1. It appears that in the southern part of zone S, where the larger, higher energetic value items are less available, the birds may find it more profitable to eat polychaetes than the small A. cycladea which have a greater handling time than worms and contain less flesh than the larger bivalves at the northern end. Harrison (2008) found that the southern section of zone S opposite East Marsh Lagoon was rarely used for foraging during summer, which may be associated with higher shore elevation and hence susceptibility to drying. The wider range of shore elevations at N1, N2 and the northern section of Zone S indicate a more reliable year-round supply of food for Pied Oystercatchers, while the broad range of sedimentary substrata in N1 suggests that this zone provides the highest diversity of prey assemblages.

Prey species for other waders

The foraging surveys of Harrison (2008) found that the diet of larger waders such as the Eastern Curlew (and Greenshank, but low sample size) consisted almost entirely of the crab Paragrapsus gaimardii. Intermediate sized waders such as Curlew Sandpiper, Bar-tailed Godwit, Whimbrel and Grey-tailed Tattler consumed high quantities of polychaetes (75-100%), but also P. gaimardii and other items in lower frequencies. The diet of the Sooty Oystercatcher was similar to that of the Pied Oystercatcher, however the former species took a higher proportion of polychaetes overall (73%; compared with ~ 40% for Pied Oystercatchers). It consumed lower numbers of the bivalves Katelysia scalarina, Anapella cycladea, mussels, other bivalves, crabs (P. gaimardii, Mictyris platycheles), the gastropod Salinator fragilis and other items, consistent with the Pied Oystercatcher diet. Smaller waders, including the Red-capped Plover, Red-necked Stint, and Double-banded Plover, also fed on polychaetes, but consumed similar or larger numbers of crustaceans dominated by amphipods.

On the basis of the above, availability of the crab Paragrapsus gaimardii is most important for the Eastern Curlew, whilst polychaetes numerically dominate the diets of intermediate waders and also contribute a considerable portion of prey for smaller waders. A discussion of the availability of these prey items is provided below for the different bays and survey zones at Lauderdale. Harrison (2008) noted dietary overlap between Pied Oystercatchers and other waders, particularly in the case of polychaetes but also for other less frequent food items. Overlap was smallest in the case of the Eastern Curlew, since P. gaimardii contributed a very minor portion (0.2%) of the Pied Oystercatcher diet.

The crab Paragrapsus gaimardii was counted in samples but not measured, since it was not a consideration for the Pied Oystercatcher model. Data to assess the availability of prey for the Eastern Curlew are therefore limited to density values, which provide an indication of the distribution of food resources but may include some individuals too small to be available as prey. Paragrapsus gaimardii was not recorded in invertebrate samples from Orielton Lagoon, while it was recorded in low densities at South Arm in summer, Mortimer Bay in spring, Barilla Bay in winter, and Five Mile Beach in spring and winter. Lauderdale and Pipeclay Lagoon were the only bays where P. gaimardii was collected in all three seasons, however this could in part be a reflection of sampling intensity since these bays contained the largest number of sampling sites (except for Orielton Lagoon in winter).

Where it was recorded, the mean abundance of Paragrapsus gaimardii per sample was in the range of 0.02-0.09. Given the low density of this species, there is likely to be a high level of stochastic noise in the density dataset. The mobile nature of the species – particularly in the case of larger individuals within the upper size range eaten by Eastern Curlews – and its diurnal variation in habitat utilisation (during the day it frequently lives under shells, but at night follows the edge of the tide) are likely to contribute to this noise. This may in part explain why the data on

102 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay the availability of P. gaimardii contrast with the foraging data, since the latter recorded Eastern Curlews feeding on this species during all seasons at Orielton Lagoon, the only bay where P. gaimardii was not recorded from any invertebrate samples, and at Five Mile Beach during summer. These discrepancies highlight difficulties in sampling low density, mobile invertebrate species, and also indicate the very selective nature of the Eastern Curlew diet.

While data collected for Paragrapsus gaimardii are therefore not highly informative with relation to spatial variation in availability of Eastern Curlew prey, the pertinent consideration for the Lauderdale IIS is the finding that the Eastern Curlews primarily utilise other bays for foraging (Orielton Lagoon, Five Mile Beach, Barilla Bay; Aquenal 2008a, Harrison 2008), although Lauderdale does provide suitable food and low numbers of birds have been observed foraging in zones N1, N2 and S (Aquenal 2008a). Invertebrate data suggest that densities of P. gaimardii are relatively uniform across the Lauderdale survey zones, although numbers were elevated in samples from the rocky habitats in N1. They were also highly elevated in the seagrass habitat at S, however seagrass typically fosters many juvenile P. gaimardii that may be too small to provide food for Eastern Curlews.

In the case of intermediate and smaller waders, the majority of the diets were dominated numerically by polychaetes, whilst being supplemented by large numbers of amphipods in smaller species. The section above on Pied Oystercatchers has already provided a detailed discussion on the availability of polychaetes and hence only a brief summary is provided here in relation to other waders. The invertebrate samples recorded the highest densities of available (i.e. ≥ 10 mm) polychaetes overall at South Arm and Mortimer Bay, followed by Lauderdale and Pipeclay Lagoon. However, all bays support populations of available polychaetes and hence provide potential food, with numbers per invertebrate sample averaged across all seasons ranging from 1.1 to 4.6.

While the Ralphs Bay locations recorded the highest available mean densities of polychaetes, the combined studies of Aquenal (2008a) and Harrison (2008) recorded the intermediate/small waders foraging in all bays, although in Mortimer Bay only the Sooty Oystercatcher (aside from the Pied Oystercatcher) was observed (Aquenal 2008a). There was no clear relationship between polychaete availability and the distribution of foraging waders, since some bays that recorded comparatively low densities of polychaetes (e.g. Orielton Lagoon) were found to be particularly important foraging sites. In these cases, high foraging pressure exerted by waders may depress prey numbers across the sandflats, particularly during the summer migrator season. It is also notable that the smaller waders appear to infrequently utilise Mortimer Bay for foraging even though invertebrate samples collected there contained a high density of polychaetes. The modelling of Atkinson and Stillman (2008) includes estimations of total available polychaete resources, based on density, size, AFDM and sandflat exposure, and hence provides a more detailed analysis of polychaete food availability in the various bays than presented here. Nevertheless, it appears likely that habitat utilisation by intermediate and small waders is influenced by a range of environmental and ecological factors and cannot be predicted on the basis of mean prey densities alone.

At Lauderdale, invertebrate samples recorded seasonally reduced densities of polychaetes at the southern end of the sandflat. This is consistent with the finding that the majority of the intermediate and smaller waders feeding at Lauderdale were observed in the northern zones. While surveys found that these waders more frequently utilised N1 than N2 (Aquenal 2008a), there was no clear difference in polychaete resources between these zones on the basis of mean density and size data.

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6 REFERENCES

Aquenal (2008a) Wader utilisation surveys in and around Lauderdale. Lauderdale Quay Proposal. Report for Cardno Pty Ltd and Walker Corporation Pty Ltd.

Aquenal (2008b) Marine and estuarine ecology literature review and field survey program. Lauderdale Quay Proposal. Report for Cardno Pty Ltd and Walker Corporation Pty Ltd.

Aquenal and Biosis (2008) Nocturnal wader surveys in and around Lauderdale. Lauderdale Quay Proposal. Report for Cardno Pty Ltd and Walker Corporation Pty Ltd.

Atkinson and Stillman (2008) Carrying capacity modelling for the Pied Oystercatcher at Lauderdale and surrounding sites. Lauderdale Quay IIS studies. British Trust for Ornithology and Bournemouth University. Report for Cardno Pty Ltd and Walker Corporation Pty Ltd.

Clarke, K.R. (1993) Non-parametric multivariate analyses of changes in community structure. Australian Journal of Ecology 18: 117-143.

Davies, P., Cook, L. and Sloane, T. (2006) Orielton Lagoon: Changes in the benthic macroinvertebrate community between 1999 and 2005. Freshwater Systems, Aquatic Environmental Consulting Service. Report to Sorell Council.

Faith, D.P., Munching, P.R. and Belbin, L. (1987) Compositional dissimilarity as a robust measure of ecological distance. Vegetation 69: 57-68.

Harrison (2008) Foraging ecology of the Pied Oystercatcher and other waders at Lauderdale and surrounding sites. Lauderdale Quay Proposal. Report for Cardno Pty Ltd and Walker Corporation Pty Ltd.

Marsh, J.A. (1982) Aspects of the ecology of three salt marshes of the Derwent region and an investigation into the role of the burrowing crab Heliograpsus haswelliams. Hons. Thesis, Zoology Department, University of Tasmania, Hobart.

Technical Advice on Water (2007) Preliminary sediment review – Ralphs Bay and East Marsh Lagoon. January 2007. Report prepared for Aquenal Pty Ltd.

West, A., McGrorty, S., Caldow, R., Durell, S., Yates, M. and Stillman, R. (2006) Sampling macro-invertebrates on intertidal flats to determine the potential food supply for waders. Centre for Ecology and Hydrology, Natural Environment Research Council, England.

Woodward, I. (1985) The structural dynamics of a tidal flat mollusc community. Unpublished PhD Thesis, Department of Zoology, University of Tasmania.

104 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Appendix 1 Geographical coordinates (WGS84) of intertidal benthic infauna sampling sites.

Bay Site Easting Northing Bay Site Easting Northing Lauderdale L1 538323 5249193 Lauderdale L52 540010 5247158 Lauderdale L2 538514 5249249 Lauderdale L53 539407 5247465 Lauderdale L3 538706 5249306 Lauderdale L54 539436 5247370 Lauderdale L4 538898 5249363 Lauderdale L55 539464 5247273 Lauderdale L5 539090 5249420 Lauderdale L56 539541 5247192 Lauderdale L6 538571 5249058 Lauderdale L57 539833 5247436 Lauderdale L7 538763 5249115 Lauderdale L58 539780 5247263 Lauderdale L8 538955 5249171 Lauderdale L59 539268 5249044 Lauderdale L9 539147 5249228 Lauderdale L60 539263 5248885 Lauderdale L10 538820 5248923 Lauderdale L61 539330 5249010 Lauderdale L11 539012 5248979 Lauderdale L62 539344 5248962 Lauderdale L12 539203 5249036 Lauderdale L63 539364 5249073 Lauderdale L13 539395 5249093 Lauderdale L64 539488 5249005 Lauderdale L14 538877 5248731 Lauderdale L65 539348 5247507 Lauderdale L15 539068 5248788 Lauderdale L66 539214 5249355 Lauderdale L16 539260 5248844 Lauderdale L67 539022 5249298 Lauderdale L17 539452 5248901 Lauderdale L68 538830 5249242 Lauderdale L18 538933 5248539 Lauderdale L69 538638 5249185 Lauderdale L19 539125 5248596 Lauderdale L70 539271 5249164 Lauderdale L20 539317 5248653 Lauderdale L71 539079 5249107 Lauderdale L21 539509 5248709 Lauderdale L72 538887 5249050 Lauderdale L22 538990 5248347 Lauderdale L73 538695 5248994 Lauderdale L23 539182 5248404 Lauderdale L74 539519 5249029 Lauderdale L24 539374 5248461 Lauderdale L75 539327 5248972 Lauderdale L25 539566 5248518 Lauderdale L76 539136 5248915 Lauderdale L26 539047 5248156 Lauderdale L77 538944 5248858 Lauderdale L27 539239 5248212 Lauderdale L78 538752 5248801 Lauderdale L28 539431 5248269 Lauderdale L79 539384 5248780 Lauderdale L29 539622 5248326 Lauderdale L80 539192 5248723 Lauderdale L30 539296 5248021 Lauderdale L81 539001 5248667 Lauderdale L31 539487 5248078 Lauderdale L82 539441 5248588 Lauderdale L32 539352 5247829 Lauderdale L83 539249 5248532 Lauderdale L33 539410 5247637 Lauderdale L84 539057 5248474 Lauderdale L34 539466 5247446 Lauderdale L85 538866 5248418 Lauderdale L35 539523 5247253 Lauderdale L86 539498 5248397 Lauderdale L36 539715 5247310 Lauderdale L87 539306 5248340 Lauderdale L37 539907 5247367 Lauderdale L88 539114 5248283 Lauderdale L38 539580 5247062 Lauderdale L89 538923 5248226 Lauderdale L39 539772 5247119 Lauderdale L90 539555 5248205 Lauderdale L40 539963 5247175 Lauderdale L91 539363 5248148 Lauderdale L41 539021 5249331 Lauderdale L92 539171 5248091 Lauderdale L42 539170 5249351 Lauderdale L93 539420 5247956 Lauderdale L43 539273 5249140 Lauderdale L94 539228 5247899 Lauderdale L44 539309 5249193 Lauderdale L95 539476 5247764 Lauderdale L45 539332 5249247 Lauderdale L96 539285 5247708 Lauderdale L46 539329 5249111 Lauderdale L97 539533 5247573 Lauderdale L47 539352 5249161 Lauderdale L98 539341 5247516 Lauderdale L48 539444 5249131 Lauderdale L99 539782 5247438 Lauderdale L49 539458 5249077 Lauderdale L100 539590 5247381 Lauderdale L50 539979 5247239 Lauderdale L101 539398 5247324 Lauderdale L51 540022 5247208 Lauderdale L102 539839 5247246

105 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Bay Site Easting Northing Bay Site Easting Northing Lauderdale L103 539647 5247189 South Arm SA17 538246 5237584 Lauderdale L104 539455 5247132 South Arm SA18 538246 5237334 Lauderdale L105 539895 5247054 South Arm SA19 538246 5237084 Lauderdale L106 539704 5246997 South Arm SA20 538246 5236834 Pipeclay Lagoon P1 542010 5244237 South Arm SA21 538246 5236583 Pipeclay Lagoon P2 542360 5244238 South Arm SA22 538246 5236334 Pipeclay Lagoon P3 542710 5244237 Orielton Lagoon O2 543410 5263116 Pipeclay Lagoon P4 542010 5243887 Orielton Lagoon O3 543410 5263016 Pipeclay Lagoon P5 542360 5243887 Orielton Lagoon O4 543410 5262916 Pipeclay Lagoon P6 542710 5243887 Orielton Lagoon O5 543510 5263216 Pipeclay Lagoon P7 543410 5243537 Orielton Lagoon O6 543510 5263116 Pipeclay Lagoon P8 542010 5243187 Orielton Lagoon O7 543610 5263116 Pipeclay Lagoon P9 542710 5243188 Orielton Lagoon O8 543610 5263016 Pipeclay Lagoon P10 543060 5243187 Orielton Lagoon O9 543710 5263016 Pipeclay Lagoon P11 543410 5243187 Orielton Lagoon O10 543710 5262916 Pipeclay Lagoon P12 541660 5242837 Orielton Lagoon O11 543810 5263016 Pipeclay Lagoon P13 542519 5242858 Orielton Lagoon O12 543810 5262916 Pipeclay Lagoon P14 543060 5242837 Orielton Lagoon O13 543910 5262916 Pipeclay Lagoon P15 541660 5242488 Orielton Lagoon O14 544010 5262615 Pipeclay Lagoon P16 542360 5242487 Orielton Lagoon O15 543910 5262615 Pipeclay Lagoon P17 542838 5242480 Orielton Lagoon O16 544010 5262716 Pipeclay Lagoon P18 543060 5242487 Orielton Lagoon O17 543910 5262716 Pipeclay Lagoon P19 542360 5242137 Orielton Lagoon O18 544010 5262816 Pipeclay Lagoon P20 542710 5242137 Orielton Lagoon O19 543910 5262816 Pipeclay Lagoon P21 543060 5242138 Orielton Lagoon O20 543810 5262816 Pipeclay Lagoon P22 543410 5242137 Orielton Lagoon O21 543710 5262816 Pipeclay Lagoon P23 543760 5242137 Orielton Lagoon O22 543610 5262916 Pipeclay Lagoon P24 543760 5241788 Orielton Lagoon O23 543510 5263016 Pipeclay Lagoon P25 542360 5241437 Orielton Lagoon O24 543510 5262916 Pipeclay Lagoon P26 543410 5241437 Orielton Lagoon O25 543510 5262816 Pipeclay Lagoon P27 543760 5241437 Orielton Lagoon O26 543510 5262715 Pipeclay Lagoon P28 542710 5241087 Orielton Lagoon O27 543510 5262615 Pipeclay Lagoon P29 543060 5241087 Orielton Lagoon O28 543510 5262515 Pipeclay Lagoon P30 543410 5241087 Orielton Lagoon O29 543510 5262415 Pipeclay Lagoon P31 542710 5240737 Orielton Lagoon O30 543510 5262315 Pipeclay Lagoon P32 543060 5240738 Orielton Lagoon O31 543510 5262215 Pipeclay Lagoon P33 542609 5244185 Orielton Lagoon O32 543410 5262215 South Arm SA1 535246 5237084 Orielton Lagoon O33 543410 5262315 South Arm SA2 535246 5236834 Orielton Lagoon O34 543410 5262415 South Arm SA3 535246 5236584 Barilla Bay B1 539113 5259634 South Arm SA4 535246 5236334 Barilla Bay B2 539463 5259634 South Arm SA5 535246 5236084 Barilla Bay B3 539813 5259634 South Arm SA6 536246 5236834 Barilla Bay B4 540163 5259634 South Arm SA7 536246 5236584 Barilla Bay B5 539113 5259284 South Arm SA8 536246 5236334 Barilla Bay B6 539463 5259284 South Arm SA9 536246 5236084 Barilla Bay B7 539813 5259284 South Arm SA10 536246 5235834 Barilla Bay B8 540163 5259284 South Arm SA11 537246 5236584 Barilla Bay B9 540863 5259284 South Arm SA12 537246 5236333 Barilla Bay B10 539113 5258934 South Arm SA13 537246 5236084 Barilla Bay B11 539463 5258934 South Arm SA14 537246 5235834 Barilla Bay B12 539813 5258934 South Arm SA15 537246 5235583 Barilla Bay B13 540163 5258934 South Arm SA16 538246 5237834 Barilla Bay B14 540513 5258934

106 Aquenal Pty Ltd Surveys of Wader Prey Species Lauderdale Quay

Bay Site Easting Northing Bay Site Easting Northing Barilla Bay B15 540863 5258934 Barilla Bay B16 539113 5258584 Barilla Bay B17 539463 5258584 Barilla Bay B18 539813 5258584 Barilla Bay B19 540163 5258584 Barilla Bay B20 540513 5258584 Barilla Bay B21 539813 5258234 Barilla Bay B22 540163 5258234 Barilla Bay B23 540163 5259984 Barilla Bay B24 539813 5259984 Barilla Bay B25 539813 5260334 Five Mile Beach F1 542062 5259541 Five Mile Beach F2 541954 5259315 Five Mile Beach F3 542405 5259099 Five Mile Beach F4 542297 5258874 Five Mile Beach F5 542189 5258649 Five Mile Beach F6 542856 5258883 Five Mile Beach F7 542748 5258658 Five Mile Beach F8 542640 5258433 Five Mile Beach F9 543307 5258667 Five Mile Beach F10 543199 5258442 Five Mile Beach F11 543091 5258217 Five Mile Beach F12 543758 5258451 Five Mile Beach F13 543650 5258226 Five Mile Beach F14 544317 5258461 Five Mile Beach F15 542723 5258266 Mortimer Bay M1 538121 5242260 Mortimer Bay M2 537931 5242098 Mortimer Bay M3 537740 5241936 Mortimer Bay M4 537550 5241774 Mortimer Bay M5 538606 5241687 Mortimer Bay M6 538416 5241526 Mortimer Bay M7 538225 5241364 Mortimer Bay M8 538901 5240954 Mortimer Bay M9 538710 5240792 Mortimer Bay M10 538519 5240631 Mortimer Bay M11 538875 5240424 Mortimer Bay M12 538862 5240368 Mortimer Bay M13 538174 5241810 Mortimer Bay M14 538367 5241970 Mortimer Bay M15 537985 5241649 Mortimer Bay M16 537309 5242060 Mortimer Bay M17 537119 5241897 Mortimer Bay M18 538848 5241402 Mortimer Bay M19 538660 5241236 Mortimer Bay M20 538469 5241075 Mortimer Bay M21 538955 5240503 Mortimer Bay M22 538765 5240345 Mortimer Bay M23 538322 5242161 Mortimer Bay M24 538566 5241891 Mortimer Bay M25 538771 5241601

107 Aquenal Pty Ltd