CCAMLR

Ocean circulation has been identified as a major process controlling the distribution of biological material in marine systems.  Large-scale transport by the Antarctic Circumpolar Current (ACC), the Ross and Weddell Gyres, and the Antarctic Coastal Current can promote spatially complex population structure in the Southern Ocean through advection.  Antarctic silverfish (Pleuragramma antarcticum), a pelagic, neutrally buoyant notothenioid fish species, are distributed around the shelf systems of Antarctica and are considered an important species rivaling krill as prey for many birds, seals, whales, and other fish. We asked whether silverfish are distributed in independent, discrete populations along the shelf systems of the Southern Ocean or whether the large-scale circulation has led to connectivity among populations.  Hypotheses were tested by measuring the chemistry, trace elements and stable isotopes, in silverfish otoliths, and comparing the chemistry with simulated particle transport using a high resolution circulation model.  The results showed strong heterogeneity indicating four separate populations: i) in the Ross Sea, ii) on the southern Antarctic Peninsula in Marguerite Bay and off Charcot Island, iii) off Joinville Island, and iv) around the South Orkney Islands. This suggested that silverfish are not transported by the ACC, shelf processes on the West Antarctic Peninsula (WAP), or along the Weddell Front.  Using the circulation model, we built spatially explicit predictions of advective supply to areas along the WAP, and examined how interactions between silverfish life history and the Antarctic Coastal Current may structure assemblages over the continental shelf.

Information about fish species composition from region near the Ukrainian Antarctic Station «Akademik Vernadsky» (Argentine Islands, Antarctic Peninsula) during wintering 2007-2008 is presented. The quantitative indexes of different species fishes and the analysis of their dominant groups were studied. New fishes subdominant was registry with help our researches. Trematomus bernacchii was subdominant in the previous years, but during our researches Notothenia rosii prevailed already. Biological and morphometrical analyses of two groups Notothenia coriiceps from the Meek-Penola Channel and near the west coast of Grotto Island are conducted. It is exposed, that these two groups of fish species divided, probably, on the different population. Somatic indexes did not show considerable changeability, except for hepato-somatic. Individuals of both groups’ species of fish had the low indexes of adiposeness and fatness.

This work is prepared in accordance with recommendation of 4.18 WG-SAM-12 about submitting of data on fishing gears` construction that was used on Russian longliners Sparta” and “Chio Maru №3”. The trotline of a special design that was used is formed of main floating line and fastened lines with hooks and weight. This design allows avoiding fish injuries outside the mouth cavity and catching of VME-organisms to a large extent, because at the presented design of a longline each line with a weight (“barandija”) has bunch of 5-10 snoods with hooks and length of a snood is 30-40 cm or sometimes less and when fish eats the bait and trying to get away making chaotic movements, it won`t be hooked by the body because of the shortened snood.

Population-genetic structure of Antarctic toothfish (Dissostichus mawsoni) was investigated not once during the last decade and before, but in this work we present our data on DNA-analysis of recent samplings of toothfish from CCAMLR Subareas – 88.1, 58.4.1, 58.4.2 and 48.6. Our findings show difference with publishes data for several genes and present new view onto toothfish population genetic structure. Our results, based on analysis of nuclear genetic markers presented in Kuhn and Gaffney, 2008, do not support genetic differentiation of samples from Ross Dependency. Difference in allelic frequency with previously published data was also found for several loci.

Commercial exploitation of fish stocks around Elephant Island and the lower South Shetland Islands ceased after the 1989/90 season. One of the larger and most abundant species in the area, Gobionotothen gibberifons, was only lightly exploited compared to more northerly fishing grounds such as South Georgia. Six surveys were conducted by the US and Germany from 1998 to 2012 to investigate if and to what extent Antarctic fish stocks recover from exploitation and how natural causes may add to man-made perturbations on a fish stock by recruitment failure as one of them.

Data from the 1980’s and 1990’s (1983, 1985, 1986, 1987, 1996 and 1998: Kock, 1986, Kock 1987, Kock, 1998, Jones et al., 1998) demonstrated that recruitment of G. gibberifrons was normal. Recruitment began to decline substantially at the turn to the 2000’s. In 2012, the proportion of immature fish (<30 cm) in the population was less than 10%. Recruitment failure was restricted to Elephant Island and the lower South Shetland Islands. Surveys in the Antarctic Peninsula in 2006 and in the South Orkney Islands in 2009 demonstrated normal recruitment. What caused a number of years of very low recruitment around Elephant Island and the lower South Shetland Islands is still unknown.

The marbled notothenia (Notothenia rossii) was the first species targeted by commercial fishing in the Southern Ocean. The species has been heavily fished around South Georgia and Iles Kerguelen in the first half of the 1970’s and at Elephant Island in 1979/80. The closure of the fishery for this species was one of the first conservation measures the ‘Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR)’ adopted in 1985. Fish biomass within a CCAMLR Subarea or Division or part of it, is commonly estimated by targeting a number of species including N. rossii simultaneously in the same survey.  Surveys are conducted under the assumption that the target fish species are more or less evenly distributed over the area at the time of the survey. This assumption is violated in the case of N. rossii which shows an extremely skewed abundance in that a large proportion of the population tends to aggregate in small areas while most of the area of distribution is only thinly populated. In order to provide more accurate estimates we suggest modification to the way the survey is designed.