Spawning stock-recruitment relationship in pikeperch Sander lucioperca (L.) in the Baltic Sea, with temperature as an environmental effect

Abstract The pikeperch ( Sander lucioperca ) is an important target species for commercial and recreational fisheries in the Archipelago Sea, off the southwestern coast of Finland. Wide fluctuations in the year-class strength of pikeperch are linked to summer temperatures, but the role of the biomass of the spawning stock has not previously been examined. In this study, a stock–recruitment relationship with temperature as an environmental variable was fitted to stock assessment data based on a long time series of catch statistics and commercial catch samples. The mean water temperature in July–August was the most important factor determining the year class strength. The results indicate that there is also a density-dependent effect: the number of recruits produced per unit of spawning stock biomass decreases with a growing spawning stock. The coefficient of determination of the stock–recruitment model was close to 0.8. The stock–recruitment relationship is important for predicting the future year-class strength of pikeperch under different scenarios such as climate change, and for modeling the effects of fishing or fisheries management.