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Invasive crayfish decimate native populations in Sweden
21 Oct
Summary
- Introduced signal crayfish caused native noble crayfish populations to drop significantly.
- Signal crayfish carry a deadly fungal disease devastating to native species.
- Loss of native crayfish also impacts market value due to lower prices.
In the 1960s, Sweden introduced signal crayfish to bolster fishing, a decision that later proved disastrous for native noble crayfish. These newcomers carry a virulent fungal disease, known as crayfish plague, to which native populations are highly susceptible.
Noble crayfish populations have since declined drastically, with estimates suggesting up to 97 percent wiped out over the past century. This decline, exacerbated by the invasive signal crayfish, has led to the noble crayfish being classified as critically endangered in Sweden.
The economic impact is also significant, as the native noble crayfish is worth more than twice the signal crayfish on the market. Despite stricter regulations since 1994, including the designation of signal crayfish as an invasive species in 2016, illegal introductions continue.
Anglers are urged to take precautions, such as drying equipment thoroughly between water bodies. This ecological crisis in Sweden mirrors a broader European issue, where non-native species increasingly outnumber native ones, threatening aquatic ecosystems.
