Conservation of the huchen, Hucho hucho (L.), (Salmonidae) with special reference to Slovakian rivers

Abstract

Slovak Federative RepublicThe world's biggest salmonid, the huchen, Huchu hucho (L.), is now threatened with extinction, especially the nominate form-the Danubian huchen-which is confined to the basin of the River Danube. About 50 years ago the huchen occupied almost 12 000 km of river in Europe but it is now common in only about 33% of its former distribution, is rare in 28% and has disappeared from 39%. The continuous area formerly inhabited by the huchen is now disrupted into isolated sections. This large predatory fish has been pushed back to the submountain zone of rivers, and its density has decreased considerably. This is thecombined result of increased regulation of streams, damming of rivers, industrial and agricultural pollution and other factors causing the destruction of the huchen's habitat. Protective measures have been applied, involving legal restrictions, restocking, the establishment of reserves and introductions into rivers not previously inhabited by the huchen. These measures have failed due to continuing pollution of rivers and the low numbers of fingerlings available for restocking.

Regional structure despite limited mtDNA sequence diversity found in the endangered Huchen, Hucho hucho (Linnaeus, 1758)

“…Berg (1949) assumed that Hucho once had a contiguous distribution from Asia to Europe, but went extinct in the Black Sea region, resulting in a vicariant distribution, and subsequent ''speciation'' of two lineages, now recognized as Huchen and taimen. Holčik (1990) estimated that Huchen have lost two-thirds of their distribution through the effects of river regulation, hydropower development and both industrial and agricultural pollution. Within Austria, Huchen occupy only 10% (ca.…”

Model-Based Evaluation of the Effects of River Discharge Modulations on Physical Fish Habitat Quality

“…The species is listed in Annex II of the European Flora Fauna Habitat Directive [68], as an endangered species in Appendix III of the Convention on the Conservation of European Wildlife and Natural Habitats [69], and it is classified as "Endangered" on the Red List. The current main threats to the species are flow regulations from dams and water pollution [66,70,71]. The European huchen occurs at a very low density in the Isar in Munich and its tributaries, with fewer than five fishes per 100 m of river [51,52].…”

“…The European huchen occurs at a very low density in the Isar in Munich and its tributaries, with fewer than five fishes per 100 m of river [51,52]. Three habitat types that are related to different life cycle stages have been identified [66,67,[70][71][72][73][74][75][76] and were labeled HHA (Habitat for Adults), HHR (Habitat for Adults during the pre-reproduction period), and HHJS (Habitat for spawning and Juveniles) in this study (Table 1).…”

Le Huchon (Hucho hucho L.). Etat des connaissances et perspectives

“…La migration génésique est restreinte dans l'espace. Elle varie de 5 km (VIVIER et al, 1964) à 10-25 km selon l'âge et la taille des géniteurs (HOLCIK, 1990). Elle s'effectue plutôt de nuit et les animaux les plus âgés remontent en premier (WITKOWSKI, 1988).…”

“…La résorption de la vésicule dure de 140 à 160 degrés-jours (VIVIER et al, 1964). Les alevins restent sur le site de reproduction jusqu'à ce qu'ils atteignent la taille de 40 mm, puis se déplacent vers l'aval (HOLCIK, 1990).…”