Evaluating Survival of Entangled Free‐Swimming Common Bottlenose Dolphins (Tursiops truncatus truncatus ) in the Indian River Lagoon Estuary, Florid

ABSTRACT

Fishing gear interactions pose a threat to marine mammals and are a leading mortality cause for common bottlenose dolphins ( Tursiops truncatus truncatus ) inhabiting the Indian River Lagoon (IRL) estuary along Florida's east coast. Cases of life‐threatening entanglement in free‐swimming IRL bottlenose dolphins were compiled (2008–2024) to assess survival and mortality factors. Survival was defined as surviving ≥ 90 days post‐release without subsequent life‐threatening entanglement. Injury severity, entanglement configuration, and body condition were evaluated. A total of 32 entangled dolphins were documented; 62.5% were calves ( n  = 20). Rescue efforts were plausible in 22 cases (64% survived, n  = 14). Survival varied by injury severity, with increased rates with moderate injuries (91%, n  = 10) compared to severe (36%; n  = 4). Severe injuries involving bone had a 90% mortality rate ( n  = 9). Emaciated dolphins had increased mortality and 80% ( n  = 8) with severe injuries perished. Survival varied by entanglement configuration, with decreased survival for body wraps (29%, n  = 2) and flipper entanglements (50%, n  = 1). All body wraps with severe injuries perished. Chronic entanglement increases infection and amputation risk, impairs healing in malnourished individuals, and yields progressive health decline, especially in developing calves. Findings underscore the importance of prevention, early detection, and rapid response to mitigate entanglement risk for this strategic dolphin stock.