Early development of the endemic dace Telestes karsticus (Leuciscidae,Cypriniformes) in a Dinaric karst stream in Croatia

Early development of the endemic dace Telestes karsticus is described in a Dinaric karst stream in Croatia. Larvae were acquired from successful rearing in an aquarium. Basic morphometric and meristic measures of larvae were taken during 55 days of observation. The mean total length of larvae at the time of hatching was 6.45 mm. The yolk sac was completely absorbed in all larvae by day 9 post-hatching (PH), when the mouth also opened and independent feeding and intestinal function were observed. Flexion of the urostyle was completed between days 12–16 PH. The caudal fin became completely forked on day 23 PH. Formation of fin rays was complete on day 48 PH when fish fully resembled juvenile specimens. The number of soft ray fins corresponds to the adult. Understanding the early development is particularly valuable in assessing environmental impacts and recovering of this endangered species and it is essential for effective monitoring and its conservation. This is the first report of the early development for the endemic Telestes karsticus, pointing out the importance of the obtained results for the effective conservation of the species.