CCAMLR

Information on biological aspects of the finfish catches obtained in the survey of BIP Dr.  E L  Holmberg, conducted around Shag Rocks and the South Georgias Islands in April-May 2013, is presented. A total of 25 tows were taken, catches comprised sixteen finfish species, being Champsocephalus gunnari, Chaenocephalus aceratus, Notothenia rossii, Pseudochaenichthys georgianus, Patagonotothen brevicauda guntheri and Gobionotothen gibberifrons, the most frequents. The highest fish densities were found in the shelf of the South Georgias Islands. Total lengths ranged from 4 to 55 cm, 7 to 63 cm, 9 to 51 cm, 31 to 78 cm, 11 to 20 cm and 4 to 43 cm for C. gunnari, C. aceratus, P. georgianus, N. rossii, P. brevicauda guntheri and G. gibberifrons, respectively. Males and females showed a similar population structure, in a relation 1:1 in all the species analyzed.

Two length-weight relationships were estimated for C. gunnari and C. aceratus; for specimens below and above 11 cm TL. Statiscally significant differences were found between them (ANCOVA p<0.05). Length at first maturity (L50) was estimated in 26.87 cm for C. gunnari for the pooled data. No significant differences were found between males and females. Juveniles of several species were present in significant numbers.

This report presents a summary of the work conducted onboard and a preliminary description of the results obtained during the research survey. The cruise started on april 26th and returned to Mar del Plata the 21st may 2013.

The work was conducted in the CCAMLR statistical area 48.3 and its main objective was to obtain information on the status of the stocks of Chamsocephalus gunnari and Notothenia rossii.

Diet components and trophic interactions in five demersal fish caught around of South Georgia’s waters was determined. Data were obtained from samples of Champsocephalus gunnari, Chaenocephalus aceratus, Pseudochaenichthys georgianus, Notothenia rossii and Dissostichus eleginoides, on a cruise carried out during the month of May 2013, on board of RV DY Eduardo L. Holmberg (INIDEP), at depths from 74 to 240 m. Prey Specific Index of Importance (%PSIRI) by each prey in each predator and, trophic level of all predators, was determined. Cluster Analysis was implemented based on diet components of all predators. Crustaceans were dominant prey group for C. gunnari and N. rossi, whereas C. aceratus and P. georgianus shows a diet where crustaceans and fishes had similar values of %PSIRI and D. eleginoides ate only fishes. Hyperiids and euphausiids were main prey among crustacean group. Demersal fishes identify as prey, were main prey for all analyzed predators, principally those to correspond to Channichthyidae and Nototheniidae families. All analyzed predators showed values of trophic levels that located as secondary level predators. Cluster analysis shows a grouping between C. gunnari and N.rossii, whose principal preys was hyperiids and mysids and close them, C. aceratus with zooplankton and fishes in similar proportions. Both D. eleginoides and P. georgianus, which not formed any group, shows diets mainly ichthyophagous and, in the case of P.georgianus, secondarily carcinophagous.

The reproductive biology of C.gunnari, C. aceratus and P.georgianus was studied on samples taken around South Georgias and Shag Rocks. The macroscopic analysis indicated the presence of totally mature females of three species (with hydrated oocytes). C. gunnari, C. aceratus and P. georgianus  This not only confirms the spawning time of C.gunnari in South Georgias and Shag Rocks, but also suggests spawning of P.georgianus and C.aceratus. C. gunnari batch fecundity showed a potential fit to size and a lineal fit to weight and ranged from 2,500 (27 cm TL) to 21,300 (54 cm TL) hydrated oocytes. Batch fecundity values for P.georgianus and C.aceratus showed a lineal fit to size and weight, they ranged between 6,600 (47 cm TL) and 8,400 (52 cm TL) hydrated oocytes and 7,800 (55 cm TL) and 14,400 (63 cm TL) hydrated oocytes respectively. Mean relative fecundity values were 21 oocytes/g for C.gunnari and 7 oocytes/g for C.aceratus and P.georgianus. In the case of C.gunnari and P.georgianus, it was observed that relative fecundity decreased with increasing length and weight of the females. Diameter and dry weight of C.gunnari’s hydrated oocytes showed a positive relationship with female size.

In this contribution we report the presence of 6 vulnerable marine ecosystems (VME) around the South Georgias archipelago (CCAMLR Subarea 48.3). These areas, which  are proposed for inclusion in the CCAMLR VME registry, were detected during a research cruise performed by the National Institute of Fishery Research and Development (INIDEP) and the Argentine Antarctic Institute (IAA) during April-May of 2013. VMEs were established from the finding of high densities of indicator taxa through a specific sampling performed with dredge. Two indicator taxonomic groups (Porifera and Ascidiacea) dominated the biomass and were primarily responsible of reaching the proposed threshold of 10kg/1200 m² but other 11 indicator groups were also recorded. Despite the use of different gears, standardization of densities necessary to determine which areas are considered VME allowed us compare the information presented here with previous reports in the same area. Thus, owing to high diversity and abundance of indicators taxa, at least six areas around South Georgias should be considered as VME to minimize the risks caused by fishing activity in the area of the CCAMLR convention.

An accurate history of catch is an important input into the assessment of toothfish stocks, and uncertainty or bias in the amount of catch from an area must be taken into account in the assessment of a stock.

In 2013, Korea held a workshop on the anomalous CPUE data reported from some Korean vessels in data-poor exploratory fisheries (Delegation of Korea 2013). That paper requested that the data be analysed for the development and testing of plausible hypotheses to account for its inherent patterns.

One plausible hypothesis is that the catches were not reported proportionally from the areas where they were taken. For the purposes of developing an alternative catch history for these SSRUs, we use these data regarded as anomalous, along with that from other vessels fishing in the same area and season to illustrate a method for re-adjusting catches that may be area-misreported. We do this by using a standardised CPUE from these vessels to develop an estimate of the amount of catch that could plausibly be area-misreported on these vessel trips across the areas fished.

This allows the calculation of possible alternative catches in areas where reports may not reflect catches. In illustrating this approach to the vessels with anomalous CPUE, we can develop alternative catch histories that can be used to assess the sensitivity for assessments of toothfish.

We detail the procedure followed to check the Ross Sea CCAMLR fisheries data prior to using them in a stock assessment of Antarctic toothfish (Dissostichus mawsoni). The R codes used in this procedure have been made available to the Secretariat.

This paper proposes extending the trial of daytime setting of longlines between 15 and 30 April in the Patagonian toothfish longline fishery in CCAMLR Statistical Division 58.5.2 to encompass the 2013/14 and 2014/15 fishing seasons.  Extending the trial for a further two years will enable sufficient daytime fishing effort to occur in the trial period to ensure there is a proper basis for assessing whether to allow daytime fishing between 15 and 30 April on a permanent basis.