Acoustic estimates of 0-group fish abundance in the Barents Sea and adjacent waters in 1992 and 1993

Abstract

Acoustic and biological data collected during the international O-group surveys in 1992 and 1993 were used to estimate the abundance of O-group fish of 4 species; cod, haddock, redfish and polar cod. The abundances of O-group cod amounted to 107*109a nd 84 -lo9s pecimens in 1992 and 1993 respectively. These estimates are considerably higher than those arrived at by the swept volume/area method when resonable values for trawl catch efficiencies were applied. Instantaneous mortality rates of 8-9 were calculated from the acoustic estimates of O-group in August and l-group in February for cod of the 1992 and 1993 year classes. The acoustic estimates of O-group haddock abundance amounted to 12.109 and 8-lo9 specimens and the ratio between cod and haddock abundances were significantly higher for the acoustic estimates than for the traditional indices of O-group abundance. For the two year classes under observation instantaneous mortality rates of 4-5 were arrived at from the acoustic estimates of O- and l-group haddock. For O-group redfish the acoustic estimates of abundance amounted to 38-lo9 and 48.109 specimens in 1992 and 1993 respectively. The estimates z,.rived at for O-group polar cod, 100.10~ and 62-lo9 specimens, were underestimates due to insufficient acoustic coverage of the O-group polar cod distribution area in both years.