Monitoring Harbor Porpoises
The harbor porpoise is a top predator feeding on small forage fish, a year-round resident of the Salish Sea, reproduces quickly (in comparison with other cetaceans) at one calf per year, and is sensitive to environmental and anthropogenic changes, making it an ideal indicator species. However, there is surprisingly little information on a cetacean that is now relatively high in abundance in local inland waters.
We have successfully adapted traditional photo-ID techniques to a new species, the harbor porpoise, which has not been the subject of many ID studies previously due to their lack of obvious natural markings. Features such as pigmentation, coloration, scars, and dorsal fin markings are used to positively identify harbor porpoise individuals and track them over time. We have identified and re-sighted individuals over days, weeks and months. A matrix was constructed that includes 10 categories of markings, with 3-6 variables for each, allowing a standardized way to describe different identification marks. In the complex societies of marine mammals, knowing individuals allows researchers to better understand many aspects of their society such as site fidelity, behavior, grouping, habitat use, and association and movement patterns. This is particularly important for the harbor porpoise, which is a very poorly understood species.