The huchen (// //) or Danube salmon (Hucho hucho) is a large species of freshwater fish in the salmon family of order Salmoniformes. It is the type species of its genus. The huchen is endemic to the Danube basin in Europe where the remaining population is threatened by overfishing and habitat loss. Beyond the Danube basin it also occurs today in the Drava and lower Gail rivers (in Carinthia), Drina, Mur (in Styria) and Pielach rivers. Along the Inn river, around the 30 km (19 mi)-long rebuilt and renaturalized area around the Bavarian town of Mühldorf, the huchen has returned in recent years. It has been introduced elsewhere on the continent and in Morocco, but most of these populations are not self-sustaining. In historic times the huchen has also been found in the Dniestr basin. Sometimes it lives in big dam reservoirs on mountain rivers such as Lake Czorsztyn in Poland.
Appearance and behaviour
The huchen reaches about 1.5 m (4 ft 11 in) in length and more than 50 kg (110 lb) in weight. The average length is about 60 to 120 centimetres (24 to 47 in). The huchen has a slender body that is nearly round in cross-section. On the reddish brown back are several dark patches in an X or crescent shape. Smaller fish feed on the larvae of water insects or on insects dropped into the water; the larger individuals are predators of other species of fish and other small vertebrates such as mice crossing rivers.
This permanent freshwater salmonid spawns in April, once water reaches a temperature of 6 to 9 °C (43 to 48 °F). For spawning, the huchen migrates up the river, where females excavate depressions in the gravel into which they deposit their eggs, then a male releases a cloud of sperm and the female then covers the eggs with sand. Larvae hatch 30 to 35 days after fertilization.
There is a considerable commercial effort to produce huchen fry to reintroduce the species into the wild. This requires catching the adults just before spawning and keeping them in special tanks. Fry are released in appropriate places once they have reached 4 to 10 cm (1.6 to 3.9 in).
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