The river crayfish, also called freshwater crayfish , have the scientific name of Austropotamobius pallipes and are a protected variety and species at European level .
The species is in fact included in the Red List drawn up by the International Union for Conservation of Nature and Natural Resources (IUCN), where since 2010 it has been classified as a species at risk of extinction.
The scientific name derives from Austro and Potamos. Austro refers to Austria, an area where the crayfish has been present since ancient times, and potamos means ‘river’. Pallipes for the fact that the crayfish is pale compared to other similar ones that have a more vivid reddish color.
Appearance and characteristics of the crayfish
The crayfish, variety Austropotamobius pallipes , is a crustacean with an elongated, flat body protected by an “exoskeleton”, a very robust and solid external armour made of calcified chitin.
The color of the carapace varies from dark brown to olive green (some specimens are completely blue, however), which makes it difficult to see and camouflaged with the bottom of the stream in which it usually lives.
The body is divided into two easily distinguishable parts: cephalothorax and abdomen .
The cephalothorax, which ends anteriorly with a triangular structure called the “rostrum”, has two pairs of antennae, a complex mouthparts, a pair of claws (chelipeds: used for defense, predation and mating) and four pairs of legs (pereiopods: used for walking, forward!).
The abdomen is segmented and ends with the telson (a paddle-shaped tail), which allows the animal to characteristically “swim backwards” as a reaction to escape in case of danger. Females fold it to protect the eggs.
For each segment of the abdomen there is a pair of appendages ( pleopods ); these, in the female, are all the same, while in the male the first two pairs are modified into appendages (gonopods) used for reproduction.
The claws are robust and tapered, reddish-brown or black in colour . The antennae are long and thin , and the eyes are placed on small peduncles .
As for size , males can reach a length of about 10-12 cm , while females are slightly smaller and reach 8-9 cm .
The length is therefore similar to that of sea shrimp, while it is instead shorter than that of prawns, a type of decapod crustacean different from prawns, which can reach dimensions of up to 10 cm.
The crayfish is a nocturnal animal and spends the day hidden under stones or among the roots of submerged trees.
Crayfish habitat
The crayfish lives in freshwater streams in temperate regions of Europe (Spain, France, Switzerland, Italy and the states of the Balkan Peninsula overlooking the Adriatic Sea), in clean and well-oxygenated running waters, such as streams, rivers and mountain lakes. The ideal water temperature must be between 15 and 18 degrees centigrade.
The variety Austropotamobius pallipes is also present in the United Kingdom and Ireland, although this is not its territory of origin. Its diffusion in these areas of Europe is due to some French monks who imported it from continental Europe, greatly appreciating the taste of their meat.
Crayfish were also highly appreciated by the ancient Romans who ate them in large quantities, creating various recipes, not only for their excellent flavour but also for their supposed ability to hold the secret of transmutation.
In Veneto, river shrimp fed entire generations and were considered “poor food, good, to deceive hunger and not to satiate it”.
What does the crayfish eat?
The crayfish is an omnivorous animal and feeds on algae, aquatic plants, insects and molluscs . Its diet also includes other smaller crayfish.
Reproduction of the crayfish
Reproduction of Austropotamobius pallipes occurs between late winter and early spring. The male attracts the female with a nuptial dance and offers her a small piece of food to convince her to mate. The eggs (from 50 to 100 depending on the size of the female) are carried by the female under her abdomen, where they are fertilized by the male.
Hatching occurs after an incubation period that can vary from four to seven months, depending on the thermal conditions of the watercourse.
Protection of Austropotamobius pallipes at European level and in Italy
EEC Directive 92/43 which qualifies Austropotamobius pallipes as a “ species of community interest for which special conservation zones must be identified ” and as a “ species subject to collections consistent with specific management plans ” was implemented in Italy with Presidential Decrees 357/97 and 120/2003.
In Lombardy, the protection of the crayfish dates back to 1977 (LR n. 33 of 27/07/1977) by providing for the prohibition of capture, transport and trade.
Furthermore, since 2008, with the “Provision for the protection and conservation of small fauna, flora and spontaneous vegetation” (LR n. 10 of 2008), the two species Austropotamobius pallipes and Austropotamobius italicus, part of the species complex (Austropotamobius pallipes complex), have been protected.
The crayfish is threatened by fishing carried out by man for centuries and by the alteration and destruction of their habitat which are therefore punished under the laws just mentioned.
The most important protection interventions in recent years have been implemented under the LIFE programme , the Community funding instrument to contribute to the development and implementation of Community environmental legislation and policy.
River shrimp farming
The first reproductive centre for native river crayfish in Italy (Austropotamobius italicus variety) was activated in Prabione di Tignale , in the province of Brescia, thanks to the LIFE project “Redevelopment of the biocenosis in Valvestino Corno della Marogna 2” (2004-2007).
Near Prim’Alpe , in the Corni di Canzo Forest of Lombardy , in the province of Como, the second breeding centre is active , dedicated to the carinthiacus clade of Austropotamobius italicus
In these centres, a semi-natural environment is recreated for the shrimp using branches, bundles and foliage.
Farmed crayfish are released in suitable sites to increase depleted populations ( reintroduction ) or to strengthen those already present in nature that show an insufficient density to guarantee their survival ( restocking ).
In the chosen site, a few hundred young crayfish of about three months of age, born in the breeding centers, are released, for at least three consecutive years.
Italian river shrimp
The varieties of crayfish classified to date throughout the world are more than 550 but most of them are not in Italy, but in North America and Australia. Beyond Italy , even Europe does not have many native species, mainly six varieties : Astacus astacus, Astacus leptodactylus, Astacus pachypus, Austropotamobius pallipes, Austropotamobius torrentium and Austropotamobius berndhauseri.
As far as Italy is concerned, the species Austropotamobius pallipes is found in the North, in the rest of the territory, the species Austropotamobius italicus, along the Ligurian Apennines both live, in syntopy.
American crayfish and Louisiana crayfish
American crayfish (Orconectes limosus) can be distinguished from European ones only by observing the base of the claws : the former have a small spine while the latter do not have one.
Also common in the United States is the Louisiana crayfish (Procambarus clarkii), which turns red as adults. Below you can see an image