CCAMLR

A stock assessment of the Patagonian toothfish (Dissostichus eleginoides) at Kerguelen Islands (CCAMLR Division 58.5.1) was undertaken using the modelling software CASAL, based on different statistical and biological datasets: abundance estimation from the POKER 1 (2006) and 2 (2010) surveys, standardized CPUE of commercial fisheries, tag releases and recoveries by length bin,  commercial catch-at-length data... CASAL is a simple, single-sex, single-area population model. The spatial complexity in the fishery is modeled using separate fishing selectivity functions depending on the fishing zone and the type of fishing vessels (trawlers, longliners). The fishing zone for the longliners is divided into four zones (North, East, South, Skiff Bank) and into two depth zones: shallow < 1,500m; deep > 1,500m. Commercial catch are integrated in the model by CCAMLR season. A weighted combination of datasets was integrated using the effective sample sizes calculated at the level of each haul. An iteratively estimated process error was applied to the length frequency data. With an initial biomass of about 218,000 tons, the modelling tends to present results which are consistent with the stock assessments undertaken by the Australian scientific team at Heard and McDonald Islands (division 58.5.2) and over the Kerguelen Plateau. The biomass long-term projection, done for the Patagonian toothfish with a simulated 5,100 tons catch by longliners, fulfils the CCAMLR management rules.  Research studies aiming at collecting more biological data and getting a better understanding of the population spatial complexity should be continued to consolidate the model.

The long-term environmental monitoring has been provided the insight into the integral structure of marine ecosystem in a poorly investigated coastal area of Argentine Island Archipelago The structure and functioning of the local biota has a specific response of environmentally different involved elements to a series of limiting factors. Mass phyto- and zoobenthos and macro plankton species accumulate toxic heavy metals. The pollution inhibits normal reproduction of Antarctic krill, the population recruitment of which is now owing to krill aggregations brought from other areas by sea currents. Krill recruitment rate and the local abundance maximums are the determining food factors for natural consumers of the krill.

During fishing trip of F/V «Jung Woo 3» (Republic of Korea) in the Ross Sea over 29 species were found in the stomachs of the Antarctic toothfish. The main forage organisms for the toothfish were Macrourus whitsoni, fish of the family Channichthyidae, mainly Chionobathyscus dewitti, and squid, including Psychroteuthis glacialis. Fish of the family Nototheniidae, mainly Trematomus loennbergi, were dominant in the toothfish nutrition at SSRU “J” at the shelf in the vicinity of the Ross Ice Shelf. In that area the shrimp Notocrangon antarcticus played an important role in the toothfish nutrition. Cannibalism was not observed for the Antarctic Toothfish. The average points of the stomach contents at various SSRUs correlate positively with the average catches per day. Preys toothfish had length from 8 to 75 cm. Average size of victims was varied but  only average size of the ice squid was constant. in different SSRU.