CCAMLR

At the CCAMLR meeting in 2012, the Commission welcomed the offer of Germany to take the lead in developing a Weddell Sea MPA for consideration in 2014. Subsequently, the German Federal Ministry of Food, Agriculture and Consumer Protection tasked the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research to compile and analyse scientific data for identifying areas which require particular protection in the Weddell Sea. Work under this project started mid-April 2013. This progress report is based on WG-EMM-13/22 which was submitted to WG-EMM 2013 in Bremerhaven, Germany. Germany intends to update the Scientific Committee on the actual state of our project, particularly on the main proceeds of a national data workshop held in Bremerhaven early September 2013. The main objectives of this document are (i) to propose the planning area of our evaluation study, (ii) to provide an update on the data situation, (iii) to draw attention to the forthcoming (early April 2014) international expert workshop on the planning of a Weddell Sea MPA.

A multi-year plan for research by Japan and South Africa aimed at yielding a tag-based assessment of the Dissostichus resource in statistical Subarea 48.6 was adopted in 2012 and formulated in CM 41-04. This paper presents a revised work plan for the South African contribution to the second year of this research in 2013/14 and is to be read in conjunction with WG-SAM-13/11.

The local densities of Champsocephalus gunnari  observed in the 2013 survey are compared with those observed in 1994-1997. A significant increase in densities across 24 sites previously sampled was found. The comparison of the length distribution functions suggests that the stock depletion in the early 1990’s was due to recruitment collapse, probably a consequence of overfishing.

The stock of Antarctic toothfish in the CCAMLR subarea 48.4 was estimated using as the Petersen method as  640 tonnes. Application of the harvest rate used for D. eleginoides in Subarea 48.3 (γ = 0.038) gives yields of 24 t for the Antarctic toothfish in the region vs. previous estimation of 30 tonnes.

The present report re-analyses data regarding CPUE for both species of toothfish in northern area of 48.6 (SSRU 48.6A, 48.6G). This report is a re-analysis of the CPUE time series proposed in previous work (SAM 13/29) which includes all those comments and suggestions made in the last SAM meeting. Here, the  length of the line was used as effort unit and also high CPUE values reported by a Korean Vessel (Insung No 7) were further investigated by applying extreme value analysis. Antarctic and Patagonian toothfish presented a high proportion with sets in which both species are present, and thus, an analysis of catch intention was implemented by using multivariate statistical approach of the catch composition. Standardisation of CPUE was done by using Generalised Additive Models (GAM) considering temporal and location factors. A mix model using vessel nationality as random variable was also implemented.  These improvements did not change the CPUE time series in Antarctic Toohthfish and only produces minor changes in Patagonian toothfish. We believe extreme value analysis provides a useful tool to evaluate anomalous CPUE.  The same conclusion with previous work arise, the CPUE have little or none information as index of abundance and thus, it is highly recommendable to continue with the collection of the data by scientific observed and tagging and release program.

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.