analysisAnnual mean SST was obtained by averaging monthly values foreach year. Annual winter NAO indices were calculated by averagingthe indices obtained for winter months (December–February).When analysing fisheries data, fishing effort should be taken intoaccount. Several effort estimators have been used in previousstudies, such as number of fishing days, number of fishing hours,number of vessels, vessel size or vessel power (e.g. Engelhardet al., 2013; Ligas et al., 2010; Tzanatos et al., 2013). In the presentstudy, the most reliable effort estimator available for the entiretime series was the number of active fishing vessels in the studiedarea. Although this proxy to the real effort may be biased, it isexpected that this bias is stable over a large number of years,