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Signal crayfish and crayfish are quite similar so it was a good choice of species.
But signal crayfish has a slightly stronger effect on snails, mussels and on bottom vegetation, says researcher Lennart Edsman.
The decision to deploy crayfish in Lake Vättern was made after crayfish plague killed large parts of the native species crayfish.
From the first deposit of 1000 crayfish, it has been a controversial decision when it turned out that the two crayfish species could not coexist.
A complex issue
A new report from the Swedish University of Agricultural Sciences, SLU, states that signal cancer and its impact on Lake Vättern's ecosystem is a continuing complex issue.
The crayfish acts as a cleaner on the lake bottom, is eaten by larger fish and contributes to commercial fishing, but more research is needed to understand the crayfish's full effect on the surrounding flora and fauna.
Even though signal cancer brings with it many positive qualities, it also poses a threat, says Lennart Edsman.
- The major negative effects of signal cancer have on flora and fauna are not due to the cancer itself.
This is because people take crayfish from Lake Vättern and put them in other lakes, which means that they eradicate the stocks of crayfish around Lake Vättern.
In the clip above, you get to know more about Vättern's crayfish.