/ Spotlight

Studying The Ecological Impact of Salmon Sharks in the Northeast Pacific

By Alexandra G. McInturf for CICOES Magazine

One potential prey species for Salmon sharks is the Chinook salmon (shown here). To learn more about impact of these predators, Alexandra is working with collaborators who are collecting data on Chinook salmon movement and distribution.

NO MATTER WHERE YOU LIVE in the United States, it’s likely that you have heard of, seen, or even tasted salmon. They are important fish in many ways – economically, culturally, and ecologically. As a result, much research focuses on making sure we can harvest wild salmon populations sustainably; that is, without causing a decline in the harvested population. However, natural ecosystems are complicated and can be hard to predict. For some salmon populations, conservation and sustainability strategies work quite well, while other populations don’t respond as we might expect. This may be because while we can control our own actions (by limiting our fishing, for example), there are other factors affecting salmon populations that we need to consider. Key among these is predation.

In January 2022, I began my project as a CICOES postdoctoral fellow at Oregon State University. I have been collaborating with many branches of NOAA and several universities nationwide to study a potentially impactful salmon predator: the Salmon shark (Lamna ditropis). Salmon sharks are a species in the ‘mackerel shark’ group, which also includes the white shark. In fact, they closely resemble a scaled-down version of a white shark, at 6-8 feet in length. They can be found from California to Alaska, and their presence seems correlated with that of salmon. However, very little is known about the Salmon shark, including what it eats, how often, and where. Our study, which will take place through 2023, aims to fill these gaps. I am examining stomach contents of deceased individuals, taking tissue samples to see what the sharks are eating over long periods of time, and using biologging tags (like a wild animal version of FitBits) to determine how much prey Salmon sharks need to consume to compensate for their energy use. This information will be used to assess the impact of this large predator on salmon populations in Alaska, Oregon, and Washington. Ideally, it will also allow managers to consider the impact of predators like the Salmon shark when making decisions about sustainable fishing. ◆