3.12.6 Deep-water Fisheries Resources south of 63°N These resources are assessed on a bi-annual basis and 2000 is clarified below in an answer to NEAFC and Coop. Res. Rep. 242 (2000) includes an overview of Norwegian requests for further information. these resources and their status. The advice given in 3.12.6.a Answer to Special Request on the Management of Deep-water Species NEAFC requested ICES to consider the following with Use of life history parameter as a basis for regards to deep-sea species: management a) Characterize and classify the most important As noted above management should be based on deep-sea species (listed in Annex 2 in the population dynamic information. However, for deep- request) according to their life history strategies water species such data are largely lacking and much of and rank them by vulnerability to exploitation the scientific basis for management must therefore be together with more well known deep-sea species, taken from the general biology of the species. There is a e.g., redfish and Greenland halibut; well-developed theoretical framework on life history b) Clarify advice statements for stocks where little dynamics as a basis for scientific advice on exploitation. biological information is available in order to generate consistency in advice (as outlined in ICES has used life history parameters to rank the Annex I pt 1-3 of the request); species according to productivity which, according to c) Give established reference points used as basis the theoretical framework should be informative guides for statements on stock status (as outlined in on vulnerability to exploitation: Annex I pt 5 in the request); and d) Provide advice on how to improve data- S For a given fishing mortality, stocks of lower collecting systems and advice on appropriate productivity will decrease faster than more improvement for monitoring deep-sea resources productive stocks. (as outlined in Annex I pt 6 of the request). S Norway requested ICES: Once depleted, the more productive species will be able to rebuild more quickly. To evaluate the present assessment approach of treating different species of deep-water sea fish Vulnerability includes many factors in addition to resources as one unit. species life history. Some factors are biological, e.g. aspects of species biology like shoaling, migrations, habitat preferences, whereas others reflect the fisheries, This is essentially the same request as a) above. e.g., markets for the species and fleet capacity. Many Answers to the two requests are therefore combined in deep-water species are widely distributed, and features this section of the ICES advice on fishery management. of their life history may not be constant across their range or may change in response to exploitation. For Answer to point a) of the NEAFC request and to these reasons life history parameters are useful, but not Norway perfect guides to sustainable management. However, because the most and best information is available on ICES considers that evaluation of stock status on each life histories they are the primary guide at this time. species should be done based on the population dynamics of that specific species and that all deep-water Below, deep-water species are ranked by their life species should not be treated as having the same history parameters, which are indicators of productivity. population dynamics. ICES has in its advice assessed As noted above this means that those stocks ranked as the stocks individually based on available data. The more vulnerable will be those stocks for which ranking requested by NEAFC further enlightens the detrimental impacts of fishing will be more difficult to differences in population dynamics among deep-water reverse. species. ICES Cooperative Research Report No. 246 625 Ranking the deep-water species according to life the lowest fraction of the virgin biomass. Less history parameters vulnerable species were assigned higher ranks. Where the biological parameters were considered to be quite Annex II of the NEAFC lists the following species: similar between two or more species the same rank was assigned. The available data did not allow ranking of all species (or species groups) according to all parameters. Common Name Scientific Name The species with no data are listed at the top of the Blue ling Molva dypterygia tables and given no rank (as indicated by “?”). Some Ling Molva molva parameters may be highly correlated. For example, Tusk Brosme brosme longevity, growth rate and natural mortality are most Roundnose grenadier Coryphaenoides often derived from the same data, or they may rely upon rupestris the same, unverified, assumptions. It is then to be Black scabbardfish Aphanopus carbo expected that these different parameters provide the Greater silver smelt Argentina silus same species ranking. Orange roughy Hoplostethus atlanticus Red sea bream Pagellus The estimated life history parameters used to rank the bogaraveo species are taken from the literature. Numbers given Greater forkbeard Phycis blennoides may have been estimated by different methodologies, Alfonsinos Beryx spp. have wide confidence intervals, or apply to local areas or environments. Where data are available from the ICES areas they were preferred. When no information was available information was extrapolated from other Available information on life history characteristics was areas. Parameter estimates from the Mediterranean, compiled, and the deep-water species were ranked where at least growth is clearly different, were not together with three reference species; redfish (Sebastes included in the analyses. marinus and S. mentella) and Greenland halibut (Reinhardtius hippoglossoides). The three reference In order to summarise the detailed information, a simple species have been exploited for an extensive period rank average was produced and the species (or species within the ICES area, and more data on their biology groups) were ordered (Table 3.12.6.a.1). This analysis is and population dynamics are available than for other of course crude. It should be emphasised that the deep-water species. The ranking was made on the basis underlying data are of variable quality and that new of several biological parameters: longevity, growth, information is needed for several species in order to natural mortality, fecundity, and length or age at first achieve a more reliable ranking. Nonetheless, the main maturity (Tables 3.12.6.a.2-6). Rank 1 is assigned to the pattern as indicated is believed to be robust. species for which the sustainable catch level should be 626 ICES Cooperative Research Report No. 246 Table 3.12.6.a.1 Summary of ranking of the deep-water species and the reference species redfish and Greenland halibut. A low rank means high vulnerability. Cases where no rank could be assigned due to lack of information are indicated by “?”. The overall rank in the rightmost column is an average of the available ranks in each row. Life history parameter Rank average Species Longevity Growth Natural Fecundity Length (? rate Mortality and age at ignored) first maturity Greater Forkbeard 4 ? ? ? ? ? Deep water squalid sharks: Centroscymnus 2 ? 1 1 2 1.5 coelolepis Centrophorus squamosus Orange roughy 1 1 1 4 1 1.6 Roundnose grenadier 2 3 2 3 2 2.4 Sebastes 3 2 2 4 2 2.6 Greenland halibut 4 3 3 3 3 3.2 Greater silver smelt 3 5 ? 2 3 3.3 Tusk 4 ? 2 6 3 3.8 Black scabbardfish 4 6 3 ? 3 4.0 Blue ling 3 ? ? 5 4 4.0 Ling 4 ? 3 5 4 4.0 Red (Blackspot) Seabream 4 4 ? 4 5 4.3 Beryx decadactylus 5 4 ? ? 5 4.7 Beryx splendens 5 5 ? ? 5 5.0 ICES Cooperative Research Report No. 246 627 Longevity and Swan, 1996; Mace et al., 1990). For orange roughy and Sebastes, radiometric dating of otolith cores has Estimates of longevity are based upon maximum age been carried out, and the results suggest longevity in observed from otolith readings (Table 3.12.6.a.2). For accordance with otolith growth zone readings (Fenton et several species age is difficult to determine and age al., 1991; Francis 1995; Kastelle et al., 2000; Smith et readings may not be validated. Although some al., 1995). validations have been attempted, satisfactory validations in the sense of Beamish and McFarlane (1983) are only Orange roughy, roundnose grenadier, and the deep- available for few deep-water species. For orange roughy water squalids have the longest life-spans. Most of the and roundnose grenadier, age validation has been other species have intermediate longevity (15-30 yrs), carried out, but results apply only to juveniles (Gordon but the Beryx species are relatively short-lived. Table 3.12.6.a.2 Deep-water species ranked according to longevity. Rank Species Longevity (years) Authors 1 Orange roughy 125 Annala and Sullivan, 1996; Tracey and Horn, 1999 2 Roundnose grenadier >60 Allain and Lorance, 2000; Bergstad, 1990; Kelly et al., 1997 2 Deep water squalid sharks Centroscymnus coelolepis - Centrophorus squamosus 60-70 Clarke, in press, and WD 3 Sebastes 45-50 Nedreaas, 1990 3 Blue ling ~30 Bergstad and Hareide 1996; Magnusson et al. 1997 3 Greater silver smelt ~35 Bergstad, 1993 4 Greenland halibut 15-20 ICES Arctic Fisheries WG 4 Ling ~20 Bergstad and Hareide 1996; Magnusson et al. 1997 4 Tusk ~20 (?) Bergstad and Hareide 1997; Magnusson et al. 1997 4 Black scabbardfish 8 Morales-Nin et al., 1996 12 from whole otoliths FAIR 1999; BASBLACK 2000 ~25 from sections 4 Red (Blackspot) Seabream 16 Menezes et al., 2001 4 Greater Forkbeard 15 ? FAIR 1999, Sub-t. 5.12, Doc.55 5 Beryx decadactylus 13 Krug et al.,1998 5 Beryx Splendens 11 Krug et al.,1998 Growth rate fit properly the same set of length-at-age data, especially when the full age range of the population is The k parameter of the von Bertalanffy growth equation not represented in the sample.