Probabilistic maturation reaction norm trends reveal decreased size and age at maturation in an intensively harvested stock of pikeperch Sander lucioperca

Abstract

Abstract Reports of fishing-induced evolution in the maturation schedules of commercially exploited marine fishes are numerous and are alarming. Here, we analysed the probabilistic maturation reaction norms for a freshwater fish species, the pikeperch ( Sander lucioperca ), to assess whether the maturation patterns of cohorts 1993–2006 responded to intensive coastal commercial and recreational fishing in the Archipelago Sea area of the Baltic Sea. Lp 50 values estimated using individual data from catch samples revealed that maturation had shifted towards an earlier age and smaller size. Lengths-at-age showed variation, but no linear trends, whereas the condition factor decreased for most of the age groups. Cross-correlation analysis of Lp 50 values with variables describing stock size (potential social effects on maturation) and water temperature revealed no obvious growth-independent effects on the maturation trends. This suggests that fishing, in line with the life-history theory, was the most important driving factor favouring early maturation. These results suggest that fishing-induced shifts in the maturation patterns of fish are nearly ubiquitous and not limited to commercially harvested marine species. This calls for increased awareness of fishing-induced life-history changes also in coastal and inland fisheries management.