Spawning stock biomass modulation of environment - recruitment relationship in a marginal spring spawning herring (Clupea harengus membras) population

Scientific interest in the dynamics of fish recruitment dates back to the beginning of the 20th century. Since then, several studies have shown that the environment may have a stronger effect on recruitment (R) compared to that of the spawning stock biomass (SSB). By combining a suite of methods designed to detect the non-linear, non-stationary and interactive relationships, we have re-evaluated the potential drivers and their interactions responsible for the multiannual dynamics of the recruitment dynamics of the Gulf of Riga (Baltic Sea) spring spawning herring population at the longest time-span to date (1958-2015) allowing coverage of variable ecosystem conditions. R was affected significantly by prey density and the severity of the first winter. Although SSB was not a good predictor of R, adding interaction with SSB significantly improved the model, hence the effect of the two environmental variables on R was modulated by SSB. While temporal changes in the environment-R relationship were generally gradual, several abrupt changes were evident in the strength of these relationships. In addition, non-stationary, linear and non-linear relationships were observed.