In subarea 48.3 mackerel icefish (Champsocephalus gunnari) are currently assessed by a bottom trawl survey, but evidence from predators and acoustics indicates that a considerable portion of the icefish biomass is in midwater and therefore missed by the bottom trawl survey. In January 2004, a short acoustic survey on FPRV Dorada showed that mackerel icefish, of all age classes, spend time in midwater and reinforced the evidence that a bottom trawl survey significantly underestimates biomass. An acoustic survey has the potential to give a better estimate of icefish biomass, however acoustic methods need to be developed to distinguish between krill and icefish and to improve target strength estimates of icefish.
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