Insights through response to live-strandings of harbour porpoise by the Vancouver Aquarium’s Marine Mammal Rescue Centre: the secretive life of a very common cetacean

Since 2006, 6 live-stranded harbour porpoises have been recovered and presented to the Vancouver Aquarium’s Marine Mammal Rescue Centre for rehabilitation. Estimated age at stranding ranged from 6 weeks to 7 years, with younger animals stranding more frequently in the summer and early fall. Animals ranged in weight from 12.1 to 52 kg at admit. Each animal received 24-hour care by trained veterinary staff and rescue volunteers. Length of stay ranged from 2 to 168 days for animals that died during rehabilitation or that were released. Animals that strand as dependent calves are considered non-releasable and two perinatal animals that were successfully rehabilitated are permanently housed in a habitat at the Vancouver Aquarium. The causes of death in three animals include: severe metabolic compromise, hydrocephalus, and encephalomyelitis associated with Cryptococcus sp. An adult porpoise was successfully released after 168 days of care. Post-release monitoring via satellite-linked transmitter for 72 days showed wide-ranging use of the Salish Sea habitat with dives up to 254 m in depth and up to 5 min and 50 second duration. Medical challenges with stranded porpoises include diagnosis of the underlying cause of stranding, very high metabolic rate and nutritional demands particularly with neonates, and the effect of stranding on muscles and pulmonary function resulting in a requirement for intensive and prolonged supportive care. However, investigation into the causes of morbidity and mortality of live-stranded cetaceans provides detailed insight into the spread of pathogens (including diseases of zoonotic potential) and marine ecosystem health. In addition to evaluating the success of individual animals, tagging and tracking of stranded animals is an invaluable tool to investigate habitat use in animals that are normally very difficult to mark. Animals that live in public display aquaria are not only important for education but are also valuable resources for researchers for establishing physiologic normal values