Abstract

Underwater feeding strategies of cetaceans necessitate a modified upper respiratory anatomy to prevent aspiration. The elongated larynx extends through the esophagus to insert directly into the nasal passage. Separation of the digestive and respiratory tracts is assured by the palatopharyngeal sphincter muscle. While this is a tight fit, laryngeal dislocation into the esophagus can be accomplished with moderate pressure. When the larynx is dislocated, the respiratory and digestive tracts comingle and choking can occur.

Multiple single case reports exist of cetaceans choking from laryngeal obstruction caused by fish. However, multiple cases associated with a specific population have not been previously documented. We performed a retrospective evaluation of stranded bottlenose dolphins from the Indian River Lagoon to evaluate the significance of this cause of death in this population. Of the stranded animals, 293 had a decomposition status sufficient for evaluation of possible choking. Choking was identified as the cause of death in 14 cases (4.7%).

Animals presented with a fish lodged in the cranial esophagus associated with a dislocated and obstructed or compressed larynx. There was no clear sex predilection; there were eight male, five female, and one undetermined sex animal. Affected animals included 12 adults and two juvenile age class animals. The fish species involved included sheepshead (Archosargus probatocephalus) and black chin tilapia (Sarotherodon melanotheron). Three cases had fishing line and or gear associated with the lodged fish.

Cetacean choking may be related to prey characteristics. Fish with strong dorsal spines may contribute to this condition. Prey populations may influence the impact of this cause of death. Changes in prey availability and dietary preferences may alter the significance of fatal choking in cetacean populations.