BIOLOGY AND EXPLOITATION OF PIKEPERCH, STIZOSTEDION-LUCIOPERCA (L), IN THE BALTIC SEA AREA

In the Baltic Sea, there are considerable environmental gradients from north to south and from littoral areas to the open sea. These gradien ts include both abiotic (e.g. salinity and temperature) and biotic par ameters (e.g. prey and predator abundances). The Baltic Sea thus forms a variable, and with respect to salinity, extreme, environment for a typical limnetic and warm water species Like pikeperch. It is forced t o spawn in shallow inlets, estuaries and bays where salinity is lower and temperature higher than in exposed areas. Pikeperch occur mainly i n eutrophicated archipelagoes and bays where the spring and summer tem peratures are high. It has expanded its distribution in recent decades , in response to increased coastal eutrophication. Pikeperch is also f avoured by high summer temperatures, as shown by a positive correlatio n between temperature and year-class strength. Pikeperch populations a re heavily affected by human disturbances and exploitation. In many ar eas it is economically the most important species. The effects of inte nsive fishery on pikeperch populations are largely unknown, as is the ecological significance of pikeperch as a piscivorous predator.