Ichthyofauna in the Lower Course of the Sazliyka River, Southern Bulgaria: Composition, Diversity, Seasonal Dynamics and Conservation Significance

摘要

The species diversity and seasonal dynamics of the ichthyofauna in the lower course of the Sazliyka River, a left tributary of the Maritsa River, are presented. The stretch of the river from the village of Lyubenovo to the mouth was studied for a period of four years. The composition of the ichthyofauna of the river consisted of 21 fish species of eight families. The family Cyprinidae had the highest number of species – 12, with a total of 7631 captured individuals; this family included the most abundant species captured in this river: Carassius gibelio – 3414, Alburnus alburnus – 2562, Squalius orpheus – 620 and Rutilus rutilus – 531 individuals. The ichthyofauna in the lower course of the river included 18 permanently inhabiting species. Spawning migration from the Maritsa River was proven for two species (Chondrostoma vardarense and Vimba melanops), while one species (Ctenopharyngodon idella) has accidentally entered the river. Out of the four studied sampling sites, the greatest was the fish diversity at the confluence of the Sokolitsa River (after Galabovo) and at the mouth of the Sazliyka River. Seventeen species are considered of conservation significance according to the referred national and international sources. A total of three species are listed in the Bulgarian Biodiversity Act (Annexes 2 and 4), one in the Bulgarian Red Data Book, one in the Black Sea Red Data Book, three in the Bern Convention (Annex 3), 17 are in the IUCN Red List and three are in the annexes of the Habitat Directive (92/43/EEC).