Estimating Energy Sequestration and Outflow by the Harbor Porpoise, Phocoena phocoena

Harbor porpoises (Phocoena phocoena) were known to frequent San Francisco Bay (SF Bay) historically, but WWII activities in the 1940s caused them to retreat to coastal waters outside of the Golden Gate. Harbor porpoises remained absent from SF Bay for over 65 years, until 2008, when they began their return. They are currently visiting SF Bay on a daily basis and in increasing numbers. Golden Gate Cetacean Research has monitored the reintroduction of harbor porpoises into SF Bay and, using photo identification, the population has been estimated at around 650 individuals. Since these porpoises are still spending the majority of their lives outside of the Bay, and are more likely to defecate and expire in coastal waters, the majority of the energy obtained within SF Bay is transported to coastal waters. Cara is investigating the potential amount of energy removed by these porpoises from SF Bay waters and transferred to the coast on a daily basis. As returning predators in SF Bay, it is important to place porpoises back into the context of the SF Bay food web. This will provide information on the top-down effects on SF Bay, information that is currently missing from the complete picture of energy flow and nutrient cycling.

Speaker: Cara Gallagher, SF State Univ.