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.