Consequences of injuries on survival and reproduction of common bottlenose dolphins (Tursiops truncatus) along the west coast of Florida

Abstract

Accurate identification of human-induced injuries that lead to death or interfere with reproduction is important for marine mammal management, as deaths exceeding established limits can lead to restrictions on fisheries or vessel operations. The fates of cetaceans last seen swimming with attached gear, particularly in pelagic fisheries, or with vessel strike lacerations, have been difficult to predict. Survival and reproduction data from long-term research on resident common bottlenose dolphins near Sarasota, Florida were examined relative to consequences of fishing gear ingestion, line entanglements, vessel strikes, and amputations of unknown origins. Fishing hooks embedded in the throat, goosebeak, or esophagus, or line wrapped around the goosebeak, generally lead to death. Multiple, constrictive line wraps around fin insertions can lead to amputation, blood loss, impaired mobility, or infection. Dolphins with ingested gear or severe entanglements may swim away with the gear, but likely die later. Propeller injuries involving only soft tissue were often survivable. Some dolphins survived amputations of the distal ends of fins, and continued to reproduce. As a precautionary approach, dolphins with ingested gear or severe constrictive entanglements should be considered mortalities, but extrapolations of findings from coastal bottlenose dolphins to other cetaceans and different gear must be done with caution.

Behavioral responses to fishing line entanglement of a juvenile bottlenose dolphin in Shark Bay, Australia

“…For example, in Sarasota Bay, Florida, veterinary records from 1988-2006 show over 600 deceased bottlenose dolphins (Tursiops truncatus) have ingested fishing gear [15]. In addition to ingestion, entanglement in fishing gear can also result in death [16]. Studies of entanglement are usually based on necropsies or scarring [10] [16], but there are a few that have examined the impact of entanglement on cetacean behavior [17] [15] [18].…”

“…In addition to ingestion, entanglement in fishing gear can also result in death [16]. Studies of entanglement are usually based on necropsies or scarring [10] [16], but there are a few that have examined the impact of entanglement on cetacean behavior [17] [15] [18]. Virtually no studies have detailed behavioral changes based on observations of individuals before, during, and after entanglement.…”

Marine Mammals of the Gulf of Mexico

“…Vessel strikes can injure or kill a variety of marine mammals including large whales (Laist et al 2001;Panigada et al 2006) and dolphins (Wells and Scott 1997;Van Waerebeek et al 2007;Wells et al 2008). In the coastal waters of the Gulf of Mexico, marine mammals share habitat with large and increasing numbers of boats.…”

An Overview of Increasing Incidents of Bottlenose Dolphin Harassment in the Gulf of Mexico and Possible Solutions

“…Depredation of both commercial and recreational fisheries is a growing problem globally (Noke and Odell, 2002;Brotons et al, 2008;Powell and Wells, 2011). In addition, activities that bring dolphins into close proximity with fishing gear have the potential to seriously injure or kill the animals through ingestion, entanglement, or even vessel strikes (Zollett and Read, 2006;Read, 2008;Wells et al, 2008;Barco et al, 2010;Powell and Wells, 2011;Stolen et al, 2013). As more people locate to coastal areas and participate in recreational activities, the chances for close encounters increase, making local populations susceptible to disturbance, harassment, or direct attack (Samuels and Bejder, 2004;Mattson et al, 2005;Cunningham-Smith et al, 2006;Zollett and Read, 2006).…”