Crayfishing season started on August 1st
Photo: Tiit Hunt
Translation: Liis
European crayfish
European cryafish; noble crayfish Harilik jõevähk or väärisvähk Astacus astacus
The freshwater invertebrate, the European crayfish, is an omnivore. Younger specimens have a predominantly vegetable diet, for the larger individuals the energy need rises because in growing the shell has to be replaced with a bigger one and so they begin hunting for animal food. The new shell is initially soft and leathery, becoming stronger as a result of the effect of the calcium stored in the crayfish organism.
Calcium is supplied from the calcareous water bodies that the crayfish inhabit.
In the course of shell replacement limbs torn off in conflicts are regenerated. In the early years these are noticeably smaller but as years pass they achieve an almost natural and proportional size.
The European or noble crayfish has five pairs of legs; the first have turned into claws while the hind four pairs are walking legs (pereopods). The abdomen is segmented, tapering and ending with a swimming fin or telson. The colour of crayfish depends on many factors: the colour of the bottom of the water body, heredity ... In water bodies with rich vegetation they are bluish black, in water bodies with sandy bottoms paler coloured; the Eusopean crayfish cannot live in waters with muddy bottoms.
How to distinguish between males and females? Males have larger claws, females a longer carapace, broader and flatter. On the abdominal side, at the joint between the thorax and the abdomen shield the males have sexual limbs that females lack.
On August 1st the crayfishing period started in Estonia, lasting until September 1st.
(In Estonian 01.08.2013)
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