Chronic entanglement of an immature bottlenose dolphin in fishing gear in the northern Adriatic Sea, with intervention implications

Bycatch in fishing gear is one of the main threats to cetaceans globally. It is often immediately fatal, particularly for small cetaceans, but animals sometimes escape with parts of fishing gear still attached to them. Chronic entanglement is well documented in large whales, but less so in small cetaceans. We describe year-round entanglement of an immature common bottlenose dolphin, combining in-field observations and post-mortem investigations. The dolphin survived a full year without deterioration in body condition, but was subsequently fatally entangled in another gear. The 2 entanglements appeared unrelated. Necropsy confirmed good body condition and suggested the chronic entanglement could have resolved on its own. Given the scarcity of published records and its long-term nature, this case provides useful insights into the impacts of chronic entanglement and potential prospects of survival. Finally, we evaluate the appropriateness of potential intervention attempts, with implications for response decisions for small cetaceans.