Environmental benefit of different crayfish management strategies in Finland

In Finland, the nationwide strategy for crayfish management in inland waters was renewed in 2000. The main objective was to maintain and increase the stocks of indigenous noble crayfish, Astacus astacus L. In southern Finland many water courses are being chronically infected by crayfish plague. Consequently, the strategy attempts to restore the productivity of crayfish stocks by introducing plague‐resistant signal crayfish, Pacifastacus leniusculus Dana. Crayfish is the largest mobile macroinvertebrate in Finnish freshwater ecosystems and it plays an important role in the food web. It has also an economic value for recreational and commercial fishing. So far no physical impact of introducing signal crayfish or restocking noble crayfish to ecosystems has been observed. However, in the long term, signal crayfish is likely to eradicate native noble crayfish in waters where these species co‐exist. Häme and Central Finland are two neighbouring provinces adhering to different crayfish management strategies. In Häme the results of noble crayfish stockings have been poor compared with the introduction of signal crayfish. Its recreational catch has increased rapidly, resulting in new employment opportunity. In Central Finland introduction of signal crayfish is forbidden and stocking of noble crayfish has been intensive. One goal is to maintain a gene pool resource of this species.