The asp (Leuciscus aspius) is a European freshwater fish of the Cyprinid family. It is sometimes considered one of two members of the genus Aspius by some taxonomic authorities. It is protected under Appendix III of the Bern Convention and listed as least concern on the IUCN Red List.
Normally, asps are between 10 and 80 cm in length, with some reaching 120 cm, and weighing up to 12 kg. They inhabit lakes and lower reaches of rivers and estuaries. In spring, in April–June, asps migrate from lakes to streams for spawning. Spawning is triggered by the rise in temperature and usually starts at 6 °C. The eggs attach to rocks, gravel, and water plants. After around two weeks, they hatch and the fry drift downstream to calmer waters.
Asps can be found in Estonia, Lithuania, Germany, Norway, Sweden, Finland, the Czech Republic, Poland, Ukraine, Bulgaria, Romania, Russia, Switzerland, Slovenia, the Netherlands, and Belgium. In Switzerland, asps have migrated through the Rhine-Main-Danube Canal, as in Serbia, Croatia, Austria, Hungary, and Slovakia. In the eastern regions of Europe, it is a common species in flowing waters, and popular for fly and other types of fishing.