Ecology and diet of the endemic Telestes ukliva (Cyprinidae) in the Cetina River system, Croatia
The first data on the population ecology and diet of the endemic ukliva dace (Telestes ukliva Heckel, 1843) are presented. Along the Cetina River system, the ukliva dace accounted for 38.4% of the overall fish fauna abundance, but only 6.4% of total fish biomass. The ukliva dace population exhibited migratory behaviour during the year and showed a strong temporal component; inhabiting the river main course in spring and summer, and colonising springs and subterranean waters in late autumn, where most of population overwintered. Males are smaller than females, while the sex ratio at the population level was 1:1.6 in favour of males, though this varied by station. The diet can be divided into two phases; the first in the warmer part of the year when feeding is intensive and Simuliidae larvae dominated in gut contents. This was followed by the winter and early spring period, when feeding markedly decreased due to its predominant distribution in over-wintering habitats (underground waters). The highest frequency of empty stomachs and unidentifiable digested matter and detritus occurred in early spring. Although some potential pray (Coleoptera) were present in high densities of the substratum of Cetina River, they were not found in the stomach contents of the ukliva dace.