Signal crayfish – Pacifastacus leniusculus

Signal crayfish are much more mobile than the noble crayfish, even during daylight hours. Signal crayfish are fairly flexible with regard to habitat, thriving in a wide range of temperatures and surviving even in brackish water. Signal crayfish grow well even in cold water, but are less adapted than the noble crayfish to the frequent rapid cooling of waters in the autumn during the period when the crayfish mates and lays eggs. This limits the opportunities of the species to live in the north and in shallow, small water bodies prone to rapid temperature variation. It does not seem to adapt to humus-rich acidic waters as well as the noble crayfish.

The ideal habitats for signal crayfish are large, rocky or solid-bottomed lakes where the crayfish live and forage, even in deep water. The largest specimens caught in Finland have been around 20 cm in length, but specimens larger than 12 cm in length are rare. Their life span may be up to 20 years.

European names:signal kräfta, signal crayfish, signalkrebs, écrevisse de californie, l´écrevisse signal, cangrejo senjal, californische rivierkreeft

American names:signal crayfish, Pacific crayfish, Californian crayfish