Alien fish species in northernmost Finland

Lake Inari is a large, subarctic, oligotrophic and regulated lake. The fish community of the lake is composed of 10 indigenous species, mostly salmonids. Three new species – lake trout (Salvelinus namaycush), land-locked salmon (Salmo salar m. sebago) and vendace (Coregonus albula) – were introduced into the watershed in the 1950s and 1960s. Vendace established a selfreproducing population in the lake that expanded dramatically, creating a boom in fisheries and new fishing technology in the area. The stock collapsed in the early 1990s but has rebounded in the 2000s. Lake trout and land-locked salmon have not established self-reproducing populations; the catches of these species are based on stocking.

Two large reservoirs, Lokka and Porttipahta, were created in the region in the late 1960s for the needs of hydroelectric power plants. The fish community in the reservoirs is composed of 14 native species. An alien species, peled (Coregonus peled), was introduced in 1972 to utilise the zooplankton production of the new, extensive open water areas. Peled established a self-reproducing population in the reservoirs in the 1980s and expanded rapidly, creating a fisheries boom and stimulating new fishing technology around 1990. Its recruitment and stock subsequently declined dramatically, however, causing problems for fisheries and management. Today, the low peled stock is composed of both a continuously stocked and occasionally naturally  reproducing fish population.

The four alien species – lake trout, land-locked salmon, vendace and peled – have not  hybridised with native fishes or had any serious ecological impacts on native fish communities. They comprise an economically important, additional catch in both Lake Inari and the reservoirs.