Dramatic adaptive response of life history trait to reduced commercial harvest in a freshwater fish

Fisheries-induced evolution of exploited fish stocks toward maturation at smaller sizes and younger ages has been postulated to reduce stock productivity and depress the recovery of stocks after collapse.  Moreover, evidence from empirical and modeling research has shown that evolutionary changes in maturation may be very slow or impossible to reverse, even following complete fisheries closures.  We evaluated temporal trends in maturation of five Great Lakes stocks of yellow perch (Perca flavescens) using indices that reflect plastic (age at 50% maturity) and adaptive (probabilistic maturation reaction norms; PMRNs) variation in maturation schedules.  Four of the populations were fished commercially throughout the time series, while one (Lake Michigan) experienced a fisheries moratorium following collapse of the stock.  We documented a dramatic, adaptive increase in PMRNs of the Lake Michigan stock coincident with the closure of the commercial fishery, while populations that were continuously fished showed little change.  This evidence is among the first to suggest that fish life history traits have the potential to rapidly respond to fishing moratoriums and recover from previous, fisheries-induced changes, meaning some stocks may retain the evolutionary ability to recover from commercial overexploitation.