Norwegian acoustic survey of North East Arctic cod on the spawning grounds off Lofoten

Abstract

An acoustic survey of the spawning stock of North East Arctic Cod off Lofoten has been performed annually in March-April since 1982. The estimates for 1985-1997 have been recalculated and mean length and weight at age are shown together with the abundance indices (both numbers and biomass). The abundance indices for each age are compared with VPA results from a reasonably converged part of the series. It is shown that the VPA tuning assumption of constant log catchability at age should not be used for this survey series. As the survey produces abundance indices for the mature part of the cod stock these indices should be corrected with proportions mature before they are used in traditional assessment methods estimating year class strength.