Coastal fish communities along the northern coast of the Gulf of Finland, Baltic Sea: Responses to salinity and eutrophication

The Gulf of Finland is an elongated estuarine sea receiving a large freshwater input and nutrient load, especially in the east from the River Neva. The surface water salinity of the gulf increases from < 1 to 6<parts per thousand> from east to west, and the less haline eastern areas of the gulf are the most eutrophied. Five study areas in the archipelago zone were surveyed with multimesh gill nets in summer 1998. Our results confirmed that salinity is an important factor influencing species richness in the northern coastal waters of the Gulf of Finland, as marine species gradually disappeared towards the less haline eastern areas. However, the conventional indicators of eutrophication derived from lakes (high total catches, high catches of cyprinids) did not show logical differences between more and less eutrophic coastal areas. The higher productivity in the eastern part of the gulf has not led to higher fish biomasses in the archipelago zone. A potential factor affecting fish communities seems to be the high fishing pressure in some coastal areas.