Freshwater fish assemblages in Cyprus with emphasis on the effects of dams

Background. The distribution of freshwater fishes in Cyprus is poorly known. The island is particularly interesting because of its biogeographical isolation and the long-term influence of humans on the biota, especially due to the recent damming of many rivers. This study documents preliminary baseline freshwater fish assemblage patterns including insights on the impact of the dams. Materials and methods. Site-specific fish presence data were gathered using a backpack electrofishing device, literature reviews and unstructured expert interviews. Results. A total of 53 aquatic sites in 18 river basins of Cyprus were surveyed, most of which have dam reservoirs along parts of their channels. The survey confirms the existence of sixteen fish species of which 12 are non-indigenous. Native species were found at very few sites, although the European eel was reported to be ubiquitous. Twenty-four sites sustained non-indigenous fish (45% occurrence at all sites, or 60% at all sites with fish present). Reservoir dams were the most species-rich generic habitats but hosted almost exclusively non-indigenous species. Conclusion. Cyprus’ streams are characterized by a scarcity of fishes. The absence of primary- and primary-like native species is attributed to the palaeogeography of the island which has not been connected to the continent since the Messinian Salinity Crisis. At present, only two peripheral (Anguilla anguilla and Salaria fluviatilis) and one secondary (Aphanius fasciatus) native inland fish species are reported. These, along with euryhaline marine transient species suffer from the extensive degradation of natural riverine habitats. Dams influence riverine fish assemblages by degrading downstream aquatic habitats, impeding fish movements, and by providing refuges for non-indigenous fish populations.