Sea trout is an anadromous form of brown trout (Salmo trutta L.). Sea trout usually live in the same water system as resident brown trout, and they can be genetically isolated from each other or breed together and genetically belong to the same population. The species is naturally distributed in northern and western Europe from the White Sea to northern Spain, including the entire Baltic Sea area. Populations are often partially migratory, i.e. one part of the population leaves the river for feeding in the sea (predominantly females migrate), while the other part stays in the river as residents. Sea trout spawn in rivers and smaller streams, often in the upper reaches or in smaller tributaries, where the nursery areas of trout are also found. They live their first (1–5) years as parr in the stream, leaving the stream as smolts for a feeding migration at sea that lasts for ½ up to 5 years, after which they return to their natal stream for spawning. Spawning may be repeated several times.

Environmental influence on the stock

Ecoregion: Baltic Sea

The fisheries


The nominal sea trout catch from the Baltic Sea was 479 tonnes in 2011, which is 199 tonnes (30%) less than in 2010 (Table 8.4.16.1). Most of the stocks in the Baltic Sea migrate in the coastal area within about 150 km of the home river and are therefore exploited locally, but longer migrations also occur in all areas, particularly in Poland, southern Sweden, and Denmark. The fish that migrate only short distances are mainly exploited in coastal and river fisheries, but long-migrants are also taken in offshore fisheries. The majority of sea trout catch is from mixed-stock fisheries.

The Main Basin is the most important area for professional sea trout catches, with the catch in this area constituting more than 60% of the total catch in 2011. Catches in the Main Basin have decreased from 1023 tonnes in 2002 to a minimum of 262 tonnes in 2008. After two years of catches around 500 tonnes, the catch fell again in 2011 to 293 tonnes. The catch of sea trout by Poland may be heavily overestimated due to possible misreporting of salmon as trout.

Around half of the total Baltic catch was taken by the coastal fishery, mainly in the Gulf of Bothnia and slightly less in the Main Basin. About one third was caught by the offshore fishery, almost exclusively by Polish vessels. River catch was 92 t in 2011. The largest part of this (41 t) was reported from Swedish rivers flowing to the Gulf of Bothnia, mainly as anglers’ catch, and from Polish rivers (39 t) as commercial catch and brood-stock fishery.

Catch in the recreational fishery is known with little accuracy and only part of it is included in the nominal catch presented above. Information has been gathered in Sweden, Finland, and Denmark in recent years, and the annual estimated catch for the Gulf of Bothnia could be as high as 400 to 500 tonnes. In Denmark, the total recreational catch in Subdivisions 22–25 in 2010 was estimated to be 346 tonnes. In spite of figures being incomplete, the share caught in the recreational fishery constitutes a significant part of the total catch, in some areas by far the largest share.

In the Gulf of Bothnia and Gulf of Finland, the fishery targeting sea trout is very limited. Instead, sea trout are caught as bycatch in fisheries targeting whitefish, pikeperch, and perch. This fishery has had a high effort level in the past ten years in Finland. A significant part of this fishery is recreational.

Catch distribution

Total catch (2011) is 0.479 kt, where 100% are landings..

Effects of the fisheries on the ecosystem

The effects of sea trout fisheries probably have a minor influence on the marine ecosystem function, but as some trout populations are at low levels fisheries in these cases have affected the biodiversity of the ecosystems, particularly in rivers. There is limited knowledge on the magnitude of these effects.

The above excerpts are from the first two pages of the ICES advice, the supporting information to this advice can be read in full at the following reference: