Non-indigenous species in Swedish waters – focus on fish and shellfish

Last changed: 20 May 2014

A non-indigenous species is a species that is transported with human aid, intentionally or unintentionally, is transported from one area to another crossing a distributional barrier ( e.g. freshwater species from North America introduced in Swedish water systems) with human aid.

Introductions of non-indigenous species and stocks can pose a threat to biodiversity in larger lakes, river systems and marine areas. If a species lacks natural enemies, can fill an empty niche and have the capacity of being introduced in high densities, the species may become invasive.

The event that probably have had most serious consequences in Sweden is the introduction of the signal crayfish, which turned out to be a vector for the crayfish plague. The spread of the crayfish plague resulted in a drastic decline of the indigenous noble crayfish which now is an endangered species.

The Department of Aquatic Resources work with several non-indigenous species and also participate in ICES working group for introduction and transporting of marine organisms (WGITMO). Contact person WGITMO: Malin Werner


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