The spread of certain alien species within Sweden is regulated in order to protect the indigenous biological diversity.

The stocking of the North American signal crayfish threatens the survival of the indigenous noble crayfish by the signal crayfish' acting as a carrier of the crayfish plague and through its competition with the noble crayfish. Therefore, permission is necessary from the local County Board of Administration before releasing signal crayfish into natural waters. It is forbidden to stock signal crayfish into waters north of the River Dalälven and on the islands of Gotland and Öland.

The stocking of alien fish species into natural waters can cause great damage to indigenous fish species. Permission from the local County Administration Board is required for stocking with alien fish species. Stocking with brook trout, lake trout and the hybrid splejk should, in the long run, not occur. Today, stocking with these fish is only permitted in waters where permission for stocking with the species has earlier been granted and where measures are taken to prevent the spread of the fish outside of the area of release. It is not permitted to release alien fish species into natural waters, with the exception of rainbow trout, brook trout, lake trout, the hybrid splejk, grass carp, and signal crayfish.