ICES reports on the implementation of the Baltic Sea Multiannual Plan
The Baltic Sea ecosystem is undergoing a fundamental change and is not in equlibrium state. This has major consequences for fisheries and ecosystem management.
1. The fisheries impact the Baltic Sea ecosystem. The most important impacts are the direct removal of predators and prey with indirect effects on the foodweb, abrasion of the seabed, disturbance of associated benthic communities, and bycatch of sensitive species. Quantification of the effects of those impacts, in respect to both fisheries and environental management objectives, has yet to be carried out.
2. The factors affecting the fish stocks include abiotic factors (e.g. temperature, salinity, oxygen), changes in spatial distribution of fish stocks in response to the abiotic factors, and biotic factors (e.g. species’ interactions, parasite infection, invasive species). The main consequences of these factors are changes in:
a. productivity of herring and sprat due to change in temperature; b. productivity and distribution of eastern Baltic cod caused by a change in oxygen content; c. the foodweb functioning due to invasive species; d. predator–prey spatial overlap.
The relative contribution of these individual environmental impacts to the overall mortality rates are currently not available.