A survey-based assessment of the Northeast Arctic cod stock

Abstract

Acoustic and bottom trawl surveys of the Northeast Arctic cod stock provide fishery independent estimates of abundance and population characteristics. Given the recent uncertainties in the catch based assessment of the stock, survey based abundance estimates of ages 5+ cod and spawning stock biomass, generated by calibrating survey indices with converged estimates from a virtual population analysis (VPA), were compared with the estimates from the annual assessments. The results indicate that the survey-based estimates were more accurate than the estimates from the annual assessments. Since the VPA abundance estimates for younger cod tend to be inaccurate, the amount of information contained in the surveys was tested indirectly by determining how well estimates based on previous survey indices could predict the following year's survey value. A time-series model of ages 3+ cod and haddock survey indices predicted the subsequent value of the cod survey index fairly accurately. It is concluded that it is likely that these fishery independent surveys are providing a more accurate assessment of the current size of the cod stock than the assessment based on combining the survey data with commercial catch statistics.