Acoustic and Bottom Trawl Surveys; How Much Information Do They Provide for Assessing the Northeast Arctic Cod Stock?
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Acoustic and bottom trawl surveys of the Northeast Arctic cod stock provide fishery independent estimates of trends in abundance and population characteristics. Given the recent uncertainties in the catch based assessment of the stock, survey based abundance estimates of ages 5+ cod, generated by calibrating the survey indices with converged estimates from a 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 survey and the VPA abundance estimates for younger cod were . inconsistent, 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 the ages 3+ cod and haddock survey indices predicted the subsequent value of the cod survey index fairly accurately. Furthermore, the Lofoten acoustic survey indicates a much greater decrease in spawning stock size over the last several years than do the VPA estimates. It is concluded that it is likely that these fishery independent surveys are providing a more accurate assessment of the current health of the cod stock than the assessment based on combining the survey data with commercial catch statistics.
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