The science of Steller stubble

An Alaska Sea Grant-supported project is within a whisker of answering some critical research questions about Steller sea lions. Literally.

University of Alaska researchers are collaborating with the Aleut Community of St. Paul Island Tribal Government (ACSPI) to uncover the ecological role of top predators such as male Steller sea lions, and how changing conditions in the Bering Sea may impact their movements and diets. To do that, they’re analyzing more than 100 whiskers from Steller sea lions and northern fur seals.

Samples from the study come from ACSPI, which maintains a collection as part of their co-management activities with NOAA, and from bycatch collected through the NOAA National Observer Program, which places trained biologists on commercial fishing vessels. Using samples from different sources enables researchers to assess variation between animals exposed to different levels of human activity and other environmental risk factors. 

“It’s hard to handle a live adult male Steller sea lion to get a sample, so programs like the fisheries observers have generated an invaluable archive of samples that can be used for scientific research,” said Amy Bishop, an assistant professor at the University of Alaska Anchorage and the project’s principal investigator. “Many communities also collect samples from harvested animals and provide them to researchers and managers. We felt it was important to not only request samples, but to start shifting the model and embed the research itself within those spaces.”

The goal of the project is to improve understanding of the impacts to Steller sea lions from changes in the Bering Sea, including warming waters, shifting fish stocks and increased human activity. First, the researchers will assess potential competition between male Steller sea lions and northern fur seals, two large pinnipeds that share foraging grounds and may be impacted differently by changing conditions. Second, they will explore how individual Steller sea lions differ in the way they forage, and how those strategies may be shaped by changing ocean conditions and interactions with fisheries. Third, the scientists will track habitat use and dietary shifts over time, especially in relation to marine heatwaves and broad-scale movements of sea lions and fur seals. 

Alaska Sea Grant is providing research funding and also supporting UAA graduate student Ben Peterson to work on the project. Bishop said the effort will fill critical knowledge gaps around predator-prey dynamics, foraging strategies, and risks of interaction between sea lions and commercial fisheries in the northern and eastern Bering Sea. “Steller sea lions are the largest of the otariids (sea lions or fur seals), with males weighing in at over 2,000 pounds during the breeding season,” noted Bishop. “With this large size, and associated appetite, males likely play an important predator role in the food web. But very little research has focused on their foraging strategies, or how that might relate to their risk of being caught in fisheries as bycatch.”  

The whiskers are critical to addressing these questions because researchers can use the samples’ carbon and nitrogen stable isotope ratios to reconstruct the animals’ foraging histories. These chemical signatures vary depending on what the animals eat, and because whiskers grow at a steady rate over time, they provide a natural timeline of diet, revealing how feeding habits have changed throughout their lives.

Peterson has been preparing the whiskers—cleaning them and trimming the nearly 20 meters of samples into 5-millimeter sections—before sending them to the Alaska Stable Isotope Facility at the University of Alaska Fairbanks for analysis. Peterson spent the summer based in the new Bering Sea Research Center on St. Paul Island, where he worked alongside residents and ACSPI employees to learn about harvests, monitoring, and Indigenous-led co-management of these marine mammals.

“Living on St. Paul Island for the summer was an experience I will never forget, especially connecting with members of the community who rely on these resources,” Peterson said.