Current issues

Many successful year classes in a row

According to the crayfish catch follow-up study, it appears obvious that the reproduction of both crayfish species has been successful for several years. A few years ago, in 2002-2003, there were poor reproduction circumstances, so that the signal crayfish year class born in 2003 was almost totally absent. With the slow-growing noble crayfish, fluctuations in the size of the catchable population are not as visible as is the case with the fast-growing signal crayfish. Since reproduction circumstances have been good in 2004-2007, and a lot of small-sized signal crayfish have been detected in test catchings, there is good reason to expect good catches for at least three or four years, i.e. until 2011.

Crayfish plague still reducing noble crayfish stocks

Indigenous noble crayfish catches collapsed 100 years ago, and despite all efforts, permanent recovery has not been reached in formerly good crayfish areas. Several re-stocked populations of noble crayfish have been destroyed by crayfish plague. The plague does not affect signal crayfish in normal circumstances, but they can be carriers of the disease.

No direct threat to noble crayfish population

Noble crayfish still occur in thousands of separate water systems. Taking into account the annual catches and growth rate, there are an estimated 15-30 million noble crayfish in Finnish waters. About 10 crayfish deaths, i.e. plaque outbreaks in a lake or river, are registered annually.

Text version