Ichthyofauna of the Vit River (Danube Basin): Composition, Distribution and Conservation Significance

ABSTRACT

Investigations on the ichthyofauna in the Vit River basin were carried out in 2007 and 2008 at 15 sampling points covering the Vit River itself and 5 tributaries in its upper stretch. Fish were sampled applying electricity according to the Standard EN14011. The results obtained were analyzed together with the data of earlier studies. Totally, 45 fish species were recorded in the basin of the Vit River until now. Twenty five of them are considered of conservation significance according to the referred national and international sources. Some of species are enlisted in several sources. Thus, 13 species are enlisted in the Bulgarian Biodiversity Act (Annexes 2 and 4), 14 are in the Bulgarian Red Data Book, 19 are in Bern Convention (Annex 3), 10 are in the IUCN Red List, and 14 are in the Habitat Directive (92/43/EEC). The most part of the Vit River basin is covered by 4 proposed protected areas of the NATURA'2000 National Network after the Directive 92/43/EEC.

The species composition of the ichthyofauna remained almost unchanged during the last 35 years. The occurrence of fish species along the river conformed to the hydro-morphological continuum depending on the habitat distribution. Significant changes were found in the recent spatial distribution of fishes in comparison with those recorded in 1970s and 1980s as a result mainly of human activities. As a whole, qualitative and quantitative impoverishment of the ichthyofauna in the upper stretch occurred due to the increasing direct and indirect human pressure. At the same time, a recovery of the fish community downstream the city of Pleven was recorded after the municipal sewage treatment plant had been put in operation.

Keywords:

• human impact
• protection
• recovering fish community
• spatial distribution
• species richness