CCAMLR

This paper presents an update of the assessment of toothfish (Dissostichus spp.) in Subarea 48.4. The Subarea is divided into two management regions and assessed using a CASAL assessment of D. eleginoides in the northern region and a simple Petersen biomass estimate derived for D. eleginoides and D. mawsoni in the southern region. The CASAL model structure used to assess the stock in 2011 has been retained although a small number of changes have been made to try to improve the fit of the model and to reduce the dependency on a relatively small amount of data. These changes comprise the addition of catch at age information for 2011, a minor change to the initial parameters of the selection pattern and the inclusion of additional information on size at age. CASAL estimates of stock size, harvest rate and recruitment are similar to those of last year’s assessment. B₀ is estimated at around 1,690 tonnes and B₂₀₁₂/B₀ at around 88%. Sustainable yield, calculated in accordance with the CCAMLR decision rules, is 63 tonnes for D.eleginoides in the northern region whilst sustainable yield calculated from the Petersen biomass estimates of Dissostichus spp. in the southern region and application of the gamma value (0.038) determined for toothfish in Subarea 48.3 was 52 tonnes. Options for the future development of the assessment of toothfish in Subarea 48.4 are considered.

• Genetic identification of grenadiers taken as bycatch in the toothfish longline fishery at South Georgia was compared with results of morphological identifications made by scientific observers and fisheries biologists.
• There was generally good agreement between methods although issues exist in the ability to morphologically distinguish between M. carinatus and M. holotrachys.
• Four species of Macrourus were identified genetically in the Southern Ocean and confirmed the presence of a recently described new species M. species.
• M. holotrachys was indistinguishable genetically from the Northern hemisphere species, M. berglax.
• There is a clear latitudinal separation of Macrourus species in the Southern Ocean.
• Latitudinal gradients in Macrourus distribution at the South Sandwich Islands reflect the patterns observed in toothfish spp.

Lepidonotothen squamifrons (Family Nototheniidae) is a demersal Southern Ocean endemic fish. Historically a commercially targeted species and common as bycatch, changes to CCAMLR fisheries regulations in 1989 have meant it is now only caught in sub-area 48.3 during research surveys. Data collected during groundfish surveys at South Georgia and Shag Rocks from 1986 to 2012 were analysed to investigate distribution, size, maturity, and diet. Distribution was patchy with aggregations in specific ‘hotspots’ to the east of Shag Rocks and the west of South Georgia. Reliable biomass estimates were not possible due to this skewed distribution creating large confidence intervals, but length-frequency analysis showed recognisable cohort progression and a trend of increasing size over time indicating a potential recovery of the stock. Mean length at first maturity for males and females (37-38cm ) was very similar to that described for the Indian Ocean basin population. Stomach content analysis (2005 - 2012) showed a varied diet dominated by salps/tunicates, but with ontogenetic and depth variations in prey composition. Enhanced knowledge of L. squamifrons in this region will be valuable in future research on habitat and foodweb modelling and spatial marine management.

Data from a seven-year (2002-2008) ichthyoplankton sampling programme in Cumberland Bay, South Georgia, sub-Antarctic (54.25^oS, 36.5^oW) were analysed to assess temporal changes in larval fish diversity and abundance. Larvae of twenty two species, representing nine families, were identified although three, Krefftichthys anderssoni (Myctophidae), Lepidonotothen nudifrons/T.hansoni (Nototheniidae) and C. gunnari (Channichthyidae), dominated abundance in all years. Significant seasonal and interannual differences in the larval fish assemblage were revealed by multivariate analyses (nMDS, ANOSIM, SIMPER). Multiple regression analyses indicated that larval abundance within Cumberland Bay was not significantly correlated with local SST or primary productivity.  Estimates of larval growth are provided for 5 abundant species. Considerable inter-specific differences in relative larval growth rate were recorded but interannual variability within species was small. However, in C. gunnari, multiple larval cohorts, representing a protracted spawning season, were observed to grow at different rates and this may be related to temperature and /or food availability. A comparison with historical growth data from South Georgia suggests there has been little change in growth rate for the main species over the last three decades.

Parasites are one of an integral part of any ecosystem and unfortunately knowledge about this ecological group in Antarctica is very scared. Partial geographical and ecological isolation of Antarctic circumpolar ecosystem plays its role on existence of endemic forms of animals, including parasites, which sometimes have unpredictably large sizes and distribution. The best example of it – Lophoura szidati. In this work we conclude the results of preliminary analysis of collected parasites of Antarctic fishes that were caught during longline fishing in seasons 2010/11 and 2011/12 in Subareas 88.1, 58.4 and 48.6.

Results of histological analysis of gonads of female and male Antarctic toothfish Dissostichus mawsoni caught in the Bellingshausen Sea in 2011- 2012 seasons are presented. Morphological indices of females and males, age, indices of gonads, fecundity, and condition by Fulton are described. In the Bellingshausen Sea the Antarctic toothfish had deferred reproductive ability compared with other subareas of the Pacific Antarctic studied previously, it was detected a low share of females with the ovaries at the stage of vitelligenous growth of oocytes (diameter 1.41-1.61 mm), and males with maturing spermatogonia. The individual absolute fecundity was 0.11-0.47 million eggs, relative fecundity –26-29 eggs per g.

Available catch, effort, catch-at-size and tagging data for Statistical Subarea 48.6 are analysed to provide preliminary assessments for Dissostichus mawsoni and D. eleginoides separately in Subarea 48.6 north of 60°S (the combined SSRUs 48.6A and 48.6G). A preliminary assessment for D. mawsoni in Subarea 48.6 south of 60°S (the combined SSRUs 48.6B through 48.6E) is given in an Appendix. An age-structured production model approach with a deterministic recruitment is applied.  Age is linked to size via a simple von-Bertalanffy equation in which variance in catch-at-length for a given age is proportional to the mean length at that age.  The model makes provision for IUU catches, insofar as this is possible given the available information.  Actual assumptions are set out in this document.  CPUE data are standardised using GLMs prior to their use in the assessments.  A simple accounting equation is used to keep track of the number of tagged animals in the population and to predict the number of recaptures per year.  The method includes recaptures for the year of release.  The tagging likelihood term is based on the Poisson mass distribution function.  The bulk of the model parameters are held constant at levels reported for other better researched toothfish stocks.

This paper presents a revised plan for research fishing by the Koryo Maru 11 for the 2012/13 fishing season, and revises and replaces WG-SAM-12/21.  The proposed research fishing is limited to Statistical Subarea 48.6.  Preliminary assessments of Dissostichus spp. stocks in Subarea 48.6 north of 60°S (SSRUs 48.6A and 48.6G) and south of 60°S (SSRUs 48.6B, 48.6C, 48.6D and 48.6E) were conducted by OLRAC-SPS (2012) – tabled at WG-FSA-12 as a separate paper. The research plan presented here draws on the results presented by OLRAC-SPS (2012) and addresses knowledge gaps highlighted by that analysis.  The preliminary assessment indicates that the historic precautionary maximum catch limit of 200 tonnes of Dissostichus spp. for Subarea 48.6 north of 60°S is sustainable and precautionary, and suggests that the historic precautionary maximum catch limit of 200 tonnes of Dissostichus spp. for Subarea 48.6 south of 60°S may be sustainable.  Therefore the historic maximum catch limits are assumed for this research plan.

In 2011/2012, a French vessel conducted its first exploratory fishing campaign in division 58.4.3a. In order to achieve a robust stock assessment that would provide advice on catch limits according to CCAMLR decision rules, it is suggested to continue the research program for the next three years. This paper is a revised proposal of WG-SAM-12/14 encouraged by 2012 SAM working group for a resubmission. The present research plan proposes to continue the mark-recapture experiment and to collect detailed catch, effort and biological data with a nearly same survey design as in the 2012. It will include a total of 28 research hauls. The objective of the experiment is to better understand the distribution of the metapopulation of toothfish centered on the Kerguelen-Heard-Crozet sector.

In 2011, AAD, the Fisheries Research and Development Corporation and Australian fishing industry conducted a joint project to study the reproductive dynamics of Patagonian toothfish (Dissostichus eleginoides) around Heard Island and the McDonald Islands (HIMI, Division 58.5.2). Gonadosomatic data was available for 12 563 individuals. The histology of male and female gonads was also analysed from specimens collected in 2011. This data confirms that toothfish spawn between July and August across a large latitudinal range along the deep slope of the Kerguelen Plateau. A comparison of macroscopic staging of gonad development with histological analysis showed macroscopic characteristics often failed to distinguish spent or resting mature animals (as confirmed by the presence of post-ovulatory follicles) from first maturing animals, and that even large mature fish may not spawn every year. As a result, the conventional method of estimating size at maturity, with stage 3 or above (according to the Kock and Kellerman (1991) scale) being assessed as mature, did not provide realistic estimates. A modified method, defining stage 2 or above as  ‘mature’, offset by two years to account for the duration of the maturation process, provided more realistic estimates. The revised ogives were shown to have a significant impact on the estimates of stock status relative to those used previously that were derived from studies of other populations of toothfish.