On possibility of using acoustic method to improve quality of Champsocephalus gunnari biomass estimates in Subarea 48.3

An attempt has been made to study icefish as an object of acoustic survey basing on the acoustic and biological data obtained by Russian RN ATLANTIDA in the area of South Georgia Island (January-February 2000). Estimation of possible target strength values was made by a comparison to TS of other fish species having similar body structure and morphological characters, as well as taking into acount chemical and physical body properties. There has been proved a comparability of Ch.gunnari length frequencies obtained from the catches by midwater trawl to those estimated with TS in situ measurements for fish recorded within the pelagic zone. Basing on the analysis of acoustic measurements and results of commercial fleet operation, there has been showed availability within the pelagic zone by daytime of Ch.gunnari, biomass of which would be out of bottom trawl survey access. It has been indicated that one of directions of improving Ch.gunnari stock state estimation could be an application of acoustic method to evaluate biomass distributed within the pelagic zone. The latter rises the problem of carrying out acoustic trawl survey to estimate Ch.gunnari biomass and distribution of species pelagic and pre-bottom concentrations.