Coastal-Fish Communities along the Northern Coast of the Gulf of Finland, Baltic Sea: Responses to Salinity and Eutrophication

Abstract

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‰ 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.

Fishes and salinities in the St Lucia estuarine system—a review

“…Similarly, low salinities prevailing in the middle and upper reaches of the Gambia Estuary (West Africa) meant that the juveniles of most marine fish species were confined to the higher salinity lower reaches of this system during the rainy season (Darboe et al 2004). Further evidence of marine fish responses to low salinity can be found in the Gulf of Finland (Baltic Sea) where salinities declined from 6 & to < 1 & along a transect and was an important factor influencing fish species richness, with marine taxa gradually disappearing as salinities declined towards the less haline eastern areas (Lappalainen et al 2000). Detailed information on the responses of marine fishes to low salinities in the St Lucia system are more limited than equivalent data collected during high salinity regimes, especially how the recruitment of the larvae and juveniles of marine taxa are influenced by widespread oligohaline conditions.…”

Surface layer salinity gradients and flow patterns in the archipelago coast of SW Finland, northern Baltic Sea

“…Thus, the horizontal and vertical salinity gradients of the Baltic Sea strongly influence the species composition and abundance of flora and fauna (e.g. Remane and Schlieper, 1972;Bäck et al, 1992;Lappalainen et al, 2000;Hänni-nen et al, 2003;Gasi unaitė et al, 2005).…”

Potential reasons for the changes in the abundance of pike, Esox lucius, in the western Gulf of Finland, 1939–2007

“…Recruitment failures in the Baltic Sea have been attributed to several factors influencing the quality of spawning and nursery areas, e.g. large-scale eutrophication and the general state of the Baltic Sea, including habitat destruction (Lappalainen et al 2000;Nilsson et al 2004a). In addition to these anthropogenic impacts, the fish stocks are influenced by large inter-annual variations in temperature, salinity and ice-cover.…”