Baltic Sea fish species and communities

The Baltic Sea fish communities consist of fish from various origins: marine species, freshwater species, migratory species and glacial relicts. Also occassional marine visitors and alien species are found in the Baltic. Representatives of these categories have different preferences for environmental conditions. For example, marine fish prefer more saline areas, freshwater fish prefer less saline areas and glacial relicts are more abundant in cold-water layers in the deeper areas. The composition of fish communities varies in different regions of the Baltic Sea in relation to different habitat characteristics of these regions with salinity, water temperature, and nutrient availability among the important factors.

The fish species found in the Baltic Sea are a mixture of marine and freshwater species adapted to the brackish (low salinity) conditions and their distribution is largely governed by salinity levels. Of the roughly 100 fish species inhabiting the Baltic Sea, about 70 marine species dominate the Baltic Proper, while some 30-40 freshwater species occur in the coastal and the innermost areas.

Marine species

Some marine species are well adapted to the Baltic conditions and occur in high population densities, giving fishing opportunities with high commercial value. Cod (Gadus morhua), Baltic herring (Clupea harengus membras), and sprat (Sprattus sprattus) comprise the large majority of the Baltic fish communities in terms of biomass and numbers (see figure below on spawning stock biomass). The marine fish species such as cod, sprat, flounder (Platichthys flesus), plaice (Pleuronectes platessa), dab (Limanda limanda), turbot (Psetta maxima) and brill (Scophthalmus rhombus) prefer more saline areas and therefore these species are more abundant in the southern Baltic and/or the Baltic proper.

Migratory species

There are several migratory fish species in the Baltic Sea. The anadromous migrators (i.e. species that live and feed mostly in the sea and migrate to fresh water to breed) include salmon (Salmo salar), sea trout (Salmo trutta), whitefish or powan (Coregonus species), vimba (Vimba vimba) and smelt (Osmerus eperlanus). The catadromous (i.e. fish that live mostly in lakes or rivers and migrate to sea to breed) eel (Anguilla anguilla) migrates a long way from the Sargasso Sea in North West Atlantic into the Baltic Sea area rivers and lakes as a juvenile and back as an adult but is at present very scarce due to human activities and damming.

Freshwater species

The Baltic Sea being at parts very low in salinity, there are quite a few freshwater fish species present, such as perch (Perca fluviatilis), pike (Esox lucius), pikeperch (Sander lucioperca), bream (Abramis brama), roach (Rutilus rutilus), burbot (Lota lota) and the only population of sea habiting vendace (Coregonus albula) in the world. These freshwater species naturally prefer the less saline areas and so they colonize mostly the coastal areas, especially in the northern Baltic where the salinity is lower. Most of these species have commercial value and some of the coastal populations are suffering from overexploitation.

Small coastal fish species

There are also many small marine and freshwater fish species of no commercial or recreational value e.g. ruffe (Gymnocephalus cernuus), whitebream (Blicca bjoerkna), rudd (Scardinius erythrophthalmus), bullhead (Cottus gobio), bleak (Alburnus alburnus), gobies (Pomatoschistus spp.), lesser sand-eel (Ammodytes tobianus), the pipefishes (Nerophis ophidion, Sygnathus typhle) and the sticklebacks (e.g. Pungitius pungitus). These fish species inhabit mainly estuarine areas. The three-spined stickleback (Gasterosteus aculeatus) can be found in high densities also in the pelagic. These small mainly coastal species can play significant roles in the ecosystem, e.g. acting as prey or food competitor for various life-history stages of other fish or as predators for other organisms. Despite the substantial role in the structure and functioning of the ecosystem, the knowledge on the population dynamics of these fish is relatively poor.

See the publications listed below and the HELCOM indicator fact sheet: Temporal development of Baltic coastal fish communities and key species

Occasional marine visitors

In addition, various fish species migrate from time to time from the North Sea into the Baltic Sea. Such species include whiting (Merlangus merlangus), European anchovy (Engraulis encrasicolus), mackerel (Scomber scombrus) and grey mullets (e.g. Liza ramada). Due to unfavourably low salinity conditions, marine visitors are unable to form self-sustaining populations in the Baltic Sea.

Glacial relicts

Our present knowledge on population status and trends of glacial relict fish species is very scarce. Eelpout (Zoarces viviparus), lumpsucker (Cyclopterus lumpus) and fourhorned sculpin (Myoxocephalus quadricornis) are more abundant in cold-water layers in deeper areas with sufficient amount of oxygen. They are present in relatively low abundances with the main distribution area in the deep areas of the northern Baltic Sea. These species are probably negatively influenced by excessive eutrophication, subsequent oxygen depletion on deep bottoms and contamination by toxic substances. Glacial relicts represent a spesific trophic function in the Baltic Sea being the only potentially abundant vertebrate predators in the deep and cold waters.

Alien species

Many of the alien fish species found in the Baltic Sea were introduced between the 1950s and the 1970s. The list includes such species as beluga sturgeon (Huso huso), sterlet (Acipenser ruthenus), the Siberian sturgeon (Acipenser baeri), the Russian sturgeon (Acipenser gueldenstaedtii), chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbusha). In addition, longnose sucker (Catostomus catostomus), Chinese sleeper (Perccottus glenii), silver carp (Hypophthalmichthys molitrix) and spotted silver carp (Aristichthys nobilis) have sometimes been found. Rainbow trout (Oncorhynchus mykiss) and a few whitefish forms (Coregonus spp.) are present due to introductions and escapes from aquaculture. However, none of these species have been able to form self-sustaining populations.

The Prussian carp (Carassius gibelio) and the round goby (Neogobius melanostomus) are now common and found in various sub-systems of the Baltic Sea. The Prussian carp (present in the Baltic Sea since early 1950s) and round goby (introduced in early 1990) have been shown to be able to reproduce in the Baltic Sea. These species have colonized new areas in recent decades and are increasing in abundance in various parts of the Baltic Sea. The round goby has been recorded to have a negative influence on ecosystems and commercially important fish species.

Click here for more information on alien species in the Baltic Sea.

See the links below for more details on the following commercial fish species :

• Cod
• Baltic herring
• Sprat
• Baltic flatfish species
• Salmon
• Sea trout
• European eel
• Sturgeon

 

	HELCOM indicator fact sheets HELCOM endangered species fact sheets Assessment of Coastal Fish in the Baltic Sea (2006) - BSEP 103a Changing Communities of Baltic Coastal Fish. Executive summary: Assessment of coastal fish in the Baltic Sea  (2006) - BSEP 103b HELCOM Red list of threatened and declining species of lampreys and fishes of the Baltic Sea (2007) - BSEP 109

 

 

Last updated 3 December 2008