Crayfish

Noble crayfish – a critically endangered species of great value

It is estimated that up to 97% of noble crayfish populations have been wiped out over the past hundred years, making the species critically endangered. The noble crayfish holds significant cultural, social, and economic value. In many parts of Sweden, efforts are underway to preserve the species through breeding and improved crayfish fishing practices.

Signal crayfish – an invasive species and a disaster for the noble crayfish

The signal crayfish, a chronic carrier of crayfish plague, was introduced to Sweden starting in the 1960s. Today, there are harvestable populations in Lake Hjälmaren and Lake Vättern, where commercial fishing increased sharply in the past, mainly due to increased use of fishing gear.

Signal crayfish have often provided good catches in southern Sweden. However, their introduction has been disastrous for the noble crayfish, whose population losses have quadrupled since the species was brought in. As a result, the signal crayfish has been classified as an invasive species since 2016, and it is no longer permitted to farm or release them. Already in 1994, it became illegal to introduce signal crayfish into new waters, but widespread illegal releases have taken place and, sadly, still occur—continuing to spread the crayfish plague. Signal crayfish can also be affected by acute crayfish plague and die if stressed.