APU partners on two research projects to assess diminishing Alaska salmon

Alaska Pacific University’s (APU) Fisheries, Aquatic Science, and Technology (FAST Lab) is partnering on two applied research projects to support Alaska’s salmon fishery management agencies in addressing ongoing declines in Chinook and Chum salmon populations. The first study on Yukon Chinook is in partnership with Alaska Department of Fish and Game (ADFG) and the USGS Western Fisheries Research Center. The partner on the second project is the Auke Bay Laboratories, which is part of the NOAA Alaska Fisheries Science Center. The first study is investigating how the Ichthyophonus parasite impacts Chinook salmon migrating to spawning grounds in the Yukon River, while the second explores how salmon’s early life diet in freshwater systems may influence the survival and body size of juvenile Chum salmon as they enter the ocean.

“These projects reflect APU’s mission to provide community-relevant research and support sustainable resource management for the state,” said Dr. Nathan Wolf, FAST Lab Principal Investigator and APU Associate Professor. “By partnering directly with agencies and listening to local concerns, we’re helping connect science to solutions.”

Investigating Ichthyophonus Infection in Yukon River Chinook

The Yukon Chinook salmon population has experienced a dramatic decline in recent years, threatening the subsistence practices of Yukon River communities and raising ecological concerns throughout the watershed. The underlying goal of this project is to assist the ADFG in their efforts to create an annual monitoring program to assess the disease severity associated with this parasite and its impact on Chinook salmon’s ability to return to spawn. “It’s been really great working with the FAST lab because there's a bunch of like-minded people working on similar-realms of science. I have four different mentors because of how collaborative this project is, and I’ve been able to take a lot of inspiration and motivation seeing everyone heavily affected by these biology issues and working so hard to try to make a change,” says Nadia Barcelona, the APU Fast Lab environmental science graduate student working on this research.

Following a pilot study in 2024, researchers received permission to collect four adult salmon from the Yukon for hatchery spawning. These fish produced approximately 9,000 juveniles, about half of which were used to support multiple research efforts, and the other half were released into lakes in the Fairbanks area. Approximately 2,000 of the juveniles were used for the APU laboratory study, which were divided into two experimental groups:

• One group was sent to the U.S. Geological Survey, Western Fisheries Research Center in Seattle for laboratory trials to assess parasite-related mortality and pathology in freshwater.

• A second group was sent to the U.S. Geological Survey, Marrowstone Marine Field Station in Nordland Washington, for similar trials in seawater conditions.

“Hopefully this work will give us a handle on what the potential effects of this parasite, and other pathogens might be on returning salmon,” explains Dr. Wolf. “This information can be integrated into management and conservation strategies.”

Exploring the Role of Freshwater Diet in Chum Salmon Survival

The second FAST Lab project investigates the declining body size and population of Chum salmon in Alaska. Researchers are studying whether the salmon’s freshwater diet influences a juvenile salmon’s ability to survive predation and starvation in its first year at sea.

Graduate student Cassidy Gebhardt, an APU marine science master’s student, is using stable isotope analysis of eye lens laminae to look at the relationship between early life diet and body size and condition at marine entry. Eye lens laminae are layers of fibrous protein that form in the eye lens of vertebrates throughout their lives– you can think of the layers like an onion. Each layer tells researchers something about the environment and diet of the creature.

“As someone who’s only ever wanted to do science, it feels like a dream,” said Gebhardt. “It’s exciting to be working on something that could provide answers to big questions about survival and resilience in Alaska’s salmon.”

By analyzing these laminae, researchers can reconstruct the fish’s early life diet and environment. Gebhardt’s findings will help determine whether better freshwater diets increase a juvenile’s size and condition at marine entry, which are factors believed to be linked to survival.

While similar methods have been applied in squid studies, this approach is relatively new for salmon, positioning Gebhardt’s work to be one of the first peer-reviewed contributions on the topic.

Currently, limited information exists on juvenile chum salmon. What researchers do know is that the average body size of chum salmon has decreased in the last four decades, as has the overall population size of chum salmon in Alaska.

Meeting Alaska’s Research and Policy Needs

Salmon are essential to Alaska’s ecosystems, cultures, and economies. They support both traditional subsistence ways of life and one of the state’s most valuable commercial industries. From 2018 to 2024, Alaska’s commercial salmon harvest averaged 166 million fish annually and generated more than $500 million annually, while Alaska’s Native subsistence harvests averaged over 700,000 fish per year between 2018 and 2020.

“FAST Lab research is rooted in the needs of Alaska,” said Dr. Wolf. “Our students and partners are working on the frontlines of real-world change, advancing science that matters to communities, managers, and future generations. We’re really happy to be in the mix.”