A case study of monofilament line entanglement in a common bottlenose dolphin (Tursiops truncatus): entanglement, disentanglement, and subsequent death.

BACKGROUND: Free-ranging common bottlenose dolphins (Tursiops truncatus) can become entangled in fishing line and other marine debris. Infrequently, dolphins can be successfully disentangled, released back into the wild, and later examined postmortem to better understand the pathology and long-term effects of these entanglements. CASE PRESENTATION: An entangled common bottlenose dolphin (Tursiops truncatus) calf was observed in the Indian River Lagoon, Florida, USA, with monofilament fishing line wrapped tightly around its maxilla. A multi-agency team successfully disentangled the dolphin for immediate release back into its natural habitat. A year after disentanglement, photos and observations indicated that the now independent calf showed a decline in body condition, characterized by grossly visible ribs and a prominent post-nuchal depression. More than 2 years post-disentanglement, the freshly dead carcass of this juvenile dolphin was recovered with extensive predation wounds. Despite the forestomach being ~ 50% full of ingesta (fish), the dolphin was emaciated. During postmortem examination, we collected and evaluated photographs and measurements of the maxillary damage resulting from the entanglement. CONCLUSION: The monofilament entanglement caused permanent, bilateral deformation of the maxillary dental arcade, including a 4.0-4.2 cm long, 0.5 cm deep linear groove where the entanglement eroded the lateral edges of the maxilla. There was no evidence of maxillary fracture and the dolphin survived for more than 2 years after disentanglement. External evidence of propeller scars and a fishing hook discovered embedded in the laryngeal mucosa at necropsy indicated repeated human interactions.

The assessment of lethal propeller strike injuries in sea mammals.

Assessment of injuries in marine mammals may be required to help authorities determine whether human activity was involved. Three cases of marine animal deaths involving propeller blade strikes are reported to demonstrate characteristic features of such cases and diagnostic difficulties that may occur. Case 1: A juvenile New Zealand fur seal (Arctocephalus forsteri) suffered two parallel linear incised wounds of the flank and died following small intestinal herniation. Case 2: An Indo-Pacific bottlenose dolphin neonate (Tursiops aduncus) died from a deeply incised wound of the left side of the head with shattering of the skull and laceration of the underlying brain.Case 3: An adult female Indo-Pacific bottlenose dolphin (T. aduncus) died from two parallel chop wounds to the torso with opening of the thoracic and abdominal cavities with fractures of the ribs and vertebrae. Given that some animals may recover, and that the carcasses of those that are killed may simply not be found or reported, it is impossible to provide an estimate of the incidence of this type of injury amongst wild sea mammals. In cases that do come to forensic attention accurate evaluation of the type of injury may potentially have great medicolegal significance. Post-mortem putrefaction and post-mortem feeding by other sea animals may complicate assessments.

Major pathologic findings and probable causes of mortality in bottlenose dolphins stranded in South Carolina from 1993 to 2006.

Although cause-of-death information on bottlenose dolphins (Tursiops truncatus) can be located in the literature, few citations include mortality data over a long period of time covering a broad geographic region. This study describes major pathologic findings and probable causes of death of bottlenose dolphins over a 14-yr period (1993-2006) for the coastal region of South Carolina. Probable causes of death for 97 cases were determined based on gross pathology and histopathology. In an additional 30 cases, probable cause of death was apparent from gross pathology alone, and carcass condition precluded histopathology. Of the 97 dolphins examined grossly and histologically, 30 (31%) likely died of infectious disease and 46 (47%) of noninfectious disease; the cause of death was unknown in 21 (22%). Bacterial infections accounted for the large majority of fatal infections and emaciation was the leading cause of noninfectious mortality. Twelve dolphins were killed by human interactions. Of the 30 dolphins diagnosed from gross examination alone, 23 likely died from human interaction and seven were killed by stingray-spine inflictions. Although the absence of consistent use of microbiology, biotoxin analysis and contaminant testing decreases the conclusiveness of the findings, this study has broad implications in establishing baseline data on causes of death of bottlenose dolphins for future studies and for the detection of emerging diseases.

Laryngeal snaring by ingested fishing net in a common bottlenose dolphin (Tursiops truncatus) off the Israeli shoreline.

We report an unusual snaring of the larynx in an adult, female common bottlenose dolphin (Tursiops truncatus). The dolphin was observed swimming and diving in Haifa Port, Israel, but was found dead the next day, 60 km south, on the coast. Postmortem examination revealed stranded-cordage, nylon filaments wrapped around the larynx, cutting through the soft tissue, and extending down into the forestomach, where a large mass of netting was found. The cachectic state of the dolphin and the subacute to chronic, hyper-plastic response of soft tissue surrounding the filaments lodged around the larynx, suggest a prolonged period of starvation, which led to the final weakness and wasting of the dolphin.