Impacts of Mixed Trophic Interactions in the Strait of Georgia: Are Seals Saving the Salmon?

• Main Author: Blubaugh, Jonathan
• Format: Text
• Language: English
• Published: Western CEDAR 2019
• Subjects: Biology; harbor seal
• Online Access: https://cedar.wwu.edu/scholwk/2019/2019_poster_presentations/44

Single species conservation has been the standard for protecting wildlife, but ecosystem-based management is becoming increasingly popular among policy makers. Ecosystem based management differs from single species conservation by accounting for complex interactions within the community and their effects on the target species that may be overlooked by a single species approach. Behind these ecosystem management policies are models that predict how changes to the ecosystem may affect the targeted species and the larger community. Harbor seals in the Strait of Georgia prey upon many species of concern, such as Pacific herring and Pacific salmon. Current ecosystem models that attempt to simulate harbor seal trophic interactions make assumptions about harbor seals, such as an equal proportion of males and females and that the two sexes consume the same prey. However, newly published data shows that male and female seals have differences in diet that could affect prey population levels based on which sex is present in a higher proportion. I aim to develop an ecosystem model that accounts for this sex difference in diet and explore how this changes the predicted consumption of salmon in the Strait of Georgia. To my knowledge, this will be the first time that the ecosystem modeling framework, Ecopath, has been used to model sex-specific interactions. This study could have wide reaching impacts since marine predators have traditionally been treated as a homogenous group, so the results from this sexually explicit model will be important for ecological modelers and fisheries managers.