Kryvokhyzhyn S. State of cetacean populations in Ukrainian waters

The thesis is devoted to multidisciplinary research of populations of three Black Sea cetaceans in Ukrainian waters: the harbour porpoise (Phocoena phocoena relicta), the common dolphin (Delphinus delphis ponticus) and the bottlenose dolphin (Tursiops truncatus ponticus). The distribution and abundance of the cetaceans have been studied in the Sea of Azov as well as in territorial and internal waters and exclusive economic zone of Ukraine in the Black Sea. It was confirmed that the Azov Sea is inhabited by harbour porpoises and bottlenose dolphins visit this sea on rare occasions whereas common dolphins do not occur in this basin at all. The bottlenose dolphin became a dominant cetacean species in the Black Sea shelf area and the common dolphin prevails in pelagic Black Sea waters. Сetacean strandings occur mainly during spring and summer. Sometimes the elevated levels of strandings corresponded with cetacean mass mortality events caused by epizootics. The species ratio among stranded harbour porpoises, common dolphins and bottlenose dolphins was estimated as 6:2:1. Harbour porpoises prevailed also in cetacean by-catch statistics. The most dangerous fishing gear turned out to be the bottom-set gillnets for turbot and spiny dogfish. Basic morphological parameters of the examined animals were found within the known limits. Some changes were revealed in the diet of Black Sea cetaceans including a series of new prey species. It was ascertained that basic food for harbour porpoises is represented by the sprat, whiting and anchovy. The pathological findings were described; the list of helminths was extended; new information was obtained regarding the extensiveness and intensity of cetacean helminthoses.