Cetacean distribution in the Thracian Sea (North Aegean Sea, Greece) related with fishing activities.

Abstract

Cetacean conservation accorded by ACCOBAMs requires relevant knowledge in the North Aegean Sea. The present study aims at obtaining such relevant data for the Thracian Sea, the northernmost point of the North Aegean Sea. The study area covers about 2000km2

in the Gulf of Kavala and around Thassos Island, in Greece. Dedicated cetacean boat surveys have been conducted since 2006, while opportunistic research platforms, including fishing boats (trawlers, purse seiners and small scale coastal vessels) were in use since autumn 2005. Up to autumn 2012, a total strip transect of 12442,7 km has been covered. Tursiops truncatus (Bottlenose dolphin) and Delphinus delphis (Common dolphin) commonly occurred in the study area, with an encounter rate (ER) of 0.38 and 0.24 groups/100km respectively. However, during fishing activities, the ERs of the two species were found to be 0.55 and 0.26 groups/100km, respectively. Stenella coeruleoalba (Striped dolphin) has also been recorded in few occasions, with ER 0.04 groups/100km, in the southern part of the study area, where the water is deeper. Grampus griseus (Risso’s dolphin) has been recorded only once during fishing operation outside the study area, close to Lemnos Island. Phocoena phocoena (Harbour porpoise) has never been observed during the research period, even if the presence is attested in the Thracian Sea by 7 stranding in the last 10 years and by a single sighting in 1997 during a preliminary study. On going research in the area includes cetacean fisheries-associations, abundance and distribution estimations and stomach-content analyses from stranded specimens.