The river crayfish or jelševec (Astacus astacus or Potamobius astacus), which we also call the noble crayfish, is a resident of freshwater inland waters. It prefers to live in slowly flowing rivers, richly overgrown with aquatic vegetation, where juvenile jelševec have plenty of hiding places under stones or among the roots of trees. Adults dig a burrow into the bank, which we call račína. This tunnel, up to 1 m long, is left by its owner only under cover of night, when it goes in search of food.
It is widespread in the southern, central and eastern parts of Slovenia; in the western part of the country it is not present. It is the only native crayfish species found in Prekmurje.
The bodies of adult males are about 15 cm long, with the largest reaching up to 25 cm. Females are considerably smaller. The color of its body is variable and matches the color of the environment in which it lives. We find all color transitions between light, sandy brown, and almost black. Its claws are uniformly colored, their surface rough, speckled with large grains. Jelševec is our largest crayfish, which can live up to 20 years, if it is lucky, of course.
As far as food goes, jelševec, as befits a crayfish, is not picky. It will devour anything it finds; clearly, the food must be of organic origin.
Jelševec used to be very widespread and common in Slovenian rivers; it was fished for everyday food and even for export. This changed when, into our regions, together with the American species of river crayfish, they introduced a fungus … crayfish plague, as we call it, which at the end of the 19th century caused the disappearance of jelševci across Europe. After several successive epidemics, jelševci survived only in some isolated bodies of water … To this day, jelševec has recovered, at least in some places, but the abundance and distribution it had before the crayfish plague epidemics has never reached again.
Today, like other native crayfish species, it is protected here and may not be fished! A new threat to its existence is water pollution from effluents. For the jelševec's well-being, it requires unregulated banks with very clean, clear and well-oxygenated water, which, unfortunately due to human interventions in the environment, is becoming increasingly rare …
