Changes in the relationship between sea temperature and recruitment of cod, haddock and herring in the Barents Sea

Cod, haddock and herring in the Barents Sea have strongly variable recruitment. For these three stocks, earlier studies have suggested a high correlation between their recruitment and a positive relationship between high temperatures and good recruitment. These hypotheses were revisited using stock assessment and temperature data for the period 1913-present. The cod-haddock and herring-haddock recruitment correlations were both significant and positive in some periods, but became insignificant towards the end of the period. Cod and herring recruitment was not significantly correlated. Recruitment variability was found to decline towards the end of the period for all species, in particular for cod. For all three stocks there is a significant positive relationship between recruitment and temperature; this relationship is strongest for haddock and weakest for herring. Recruitment was found to be low at low temperatures and variable at medium/high temperatures during the first year of life for all three species. Temperature during the first winter of life correlates positively with haddock and cod recruitment residuals. This correlation is weakened towards the end of the period for cod, but stays high for haddock. Temperature during the first summer of life correlates positively with herring recruitment during some parts of the period, but also this correlation is weakened towards the end of the period.