Is the attempt to estimate the biomass of Antarctic fish from a multi-species survey appropriate for all targeted species? Notothenia rossii in the Atlantic Ocean sector – revisited
Notothenia rossii was the fi rst target species in Southern Ocean fi sheries. The species was already heavily fished at the beginning of the 1970s. The closure of the fishery for this species in 1985 was one of the first conservation measures adopted by CCAMLR. Fish biomass within a CCAMLR subarea or part of a subarea is commonly estimated from surveys that target a number of species, including N. rossii, at the same time. These 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 is non-randomly distributed such that a large proportion of the population tends to aggregate in small areas, leaving most of the survey area only thinly populated. In order to provide more accurate estimates of the abundance of the species, it is suggested that an acoustic survey combined with a number of identification hauls might be the most promising approach to estimating the biomass of N. rossii.