Impact of Marine Traffic on the behavioural budget of bottlenose dolphins (Tursiops truncatus) in the Gulf of Antalya, Turkey

Laura Evenepoel

Coastlines are becoming increasingly developed in response to increasing human pressures within the Mediterranean Sea. This has caused an increase in marine traffic which influences the vulnerable bottlenose dolphin populations that are known to be highly coastal in the Mediterranean Sea. The current study investigates the overall effect of marine traffic on bottlenose dolphin behaviour in the Gulf of Antalya, Turkey to provide baseline information on whether current levels of marine traffic in Antalya are sustainable for the threatened bottlenose dolphins populations. Land and boat surveys were conducted to collect behavioural data using focal group scan sampling. A first order Markov Chain was used to determine the behavioural transition probabilities for control (absence of vessels) and impact situations (presence of vessels within 400m of dolphins). The results show that marine vessels affect the behavioural transitions of bottlenose dolphins considerably. Dolphins were exposed to marine vessels 33% of the time, during which they were less likely to remain feeding and more likely to start diving. These results are concerning as the potential biological effects of the observed behavioural changes are still unknown. Protected zones in the Gulf of Antalya and species-specific conservation action plans should be created to mitigate dolphin-vessel interactions.