Background. A local stock of pikeperch, Sander lucioperca (Linnaeus, 1758), is a valuable fishery resource in Parnu Bay, northern Gulf of Riga. Due to the late maturity of pikeperch in the bay, the stock is vulnerable to over-exploitation, whereas recruitment is highly dependent on climate factors. Because of its high market price, fishing pressure on the stock increased considerably in the 1990s, resulting in stock depression. To assist fishery management in Parnu Bay we have simulated the effect of several scenarios (such as: fishing mortality, climate, and young-of-the-year food supply) on the pikeperch stock, catches, and revenues generated by the fishery.

Materials and methods. A simulation system consisting of an age-structured population model, a recruitment component, and a forcing module of different climate, food supply to young-of-the-year, and fishing mortality scenarios was used to estimate the equilibrium stock size and catches under varying environmental conditions and exploitation strategies. Economic impacts of these scenarios were assessed based on the first selling price of pikeperch.

Results. Under present climate and food supply for pikeperch young-of-the-year, the Parnu Bay pikeperch stock is very sensitive to catches of immature fish. Warmer future climate conditions are likely to be beneficial for the stock, but also prey abundance for young-of-the-year influences potential stock sizes and catches. Compared to targeting its prey species, herring, which has a lower commercial value at current first selling prices, pikeperch acts as a biomeliorator, roughly doubling fisheries revenue in the bay.

Conclusion. Flexible adaptive management methods should be used to estimate the yearly allowable pikeperch catch, taking into account food supply to young-of-the-year and climate conditions influencing recruitment.