The role of fish and fisheries in Baltic Sea nutrient dynamics. Limnology and Oceanography

Many studies show that fish and fisheries management can be important to freshwater nutrient dynamics, but similar reports from marine environments are scarce. In the Baltic Sea, we estimate the removal of nutrients by the fishery to be 1.4 % and 7 % of the total nitrogen and phosphorus load to the Baltic Sea. Moreover, compared with the anthropogenic load of nutrients that reaches the open sea, the fishery removes 2.4 % and 18 % of the nitrogen and phosphorus. In addition, we show that the summer increase of fish biomass can explain up to one third of the summer decrease in ‘‘total phosphorus’ ’ in the upper 40 m of the water column. This suggests that fish may compete with primary producers (particularly cyanobacteria) for phosphorus. The fish and the fishery can thus influence nutrient dynamics in marine systems substantially, and this should be considered in ecosystem oriented fisheries management. In freshwaters, fish can be important in nutrient dynamics, and sometimes most of the pelagic phosphorus is stored in fish biomass (Bartell and Kitchell 1978; Schindler et al. 1993). Fish stock fluctuations can influence the availability of nutrients to phytoplankton, and especially young-of-the