Larynx strangulation in a resident bottlenose dolphin (Tursiops truncatus) from the Northern Adriatic Sea, Croatia

Abstract

Marine environments worldwide are affected by various anthropogenic activities, and many cetacean populations face increasing human pressures, especially those in coastal habitats. The key threats affecting common bottlenose dolphins (Tursiops truncatus) today are fishery interactions, prey depletion, habitat disturbance, pollution and climate change. The Mediterranean basin is one of the areas subjected to enormous pressure from human activities, in particular the Adriatic Sea, where bycatch represents the most frequent cause of dolphin mortality related to fisheries, followed by larynx strangulations, long-term tail entanglement and presence of fishing gear residue in the stomach. In this study, we present the first published case of a resident bottlenose dolphin from the Adriatic Sea population with a known observation history and confirmed cause of death observed in the Croatian part of the Adriatic Sea. By comparing the photographs of the dolphin’s dorsal fin taken during the post mortem examination with those obtained from boat-based surveys, we were able to identify the individual L_1834, which has been observed since 2018 along the eastern coast of the northern Adriatic Sea. Over three decades of monitoring live bottlenose dolphins and their systematic mortality surveillance in Croatian waters enabled us to gain insight into the ranging and residency pattern of the dolphin stranded in 2023 due to larynx strangulation with fishing net parts.