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Copper River Salmon Health Surveillance
The Ahtna Intertribal Resource Commission (AITRC) continued its preliminary study to assess disease and parasite burdens in sockeye and Chinook salmon in the Copper Basin. This ongoing research aims to monitor parasites such as Ichthyophonus and Anisakis species, among others, for better planning and proactive mitigation rather than scrambling to react. It also seeks to identify any diseases in Copper River salmon. Ichthyophonus can cause mortality in salmon and affect the quality of fillets, presenting a significant food security concern, though it does not pose a direct human health risk.
Funding for this project is provided by the U.S. Environmental Protection Agency (EPA) through the Indian General Assistance Program (IGAP), in partnership with the Alaska Department of Fish and Game Fish Pathology Laboratory.
Understanding Salmon Health.
A salmon’s health cannot be understood from a single measurement. Researchers look at multiple parts of each fish to develop a more complete picture of its condition.
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During sampling, crews record basic biological information such as species, length, weight, and age and collect samples including blood and plasma, heart, kidney, spleen, gastrointestinal tract, otoliths, and other tissues. Each sample can provide different information about the fish and the conditions it experienced throughout its life.
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Together, these samples allow researchers to investigate questions related to parasites, tissue health, diet, age, growth, and overall fish condition rather than relying on a single indicator of health.
Across the Copper Basin.
Sampling is designed to collect information from salmon harvested at different locations and points throughout the run. The 2024 sampling plan divided collection among three areas: Chitina, Tonsina to Gulkana, and Gakona to Slana. Sampling was also spread across approximately 10–12 weeks of the fishing season, allowing researchers to examine salmon returning at different times.
This approach provides a broader view of salmon health across both space and time, rather than relying on fish collected from a single location or a single point in the season.
Community Involvement.
Community participation is an important part of salmon health monitoring. Working with local fishermen and subsistence users provides opportunities to collect samples from salmon already being harvested while connecting research directly with the people who rely on Copper River salmon.
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Community-based sampling also helps expand where and when fish can be examined across the watershed. The project presentation highlights community involvement as a central component of the sampling program and shows sampling conducted at multiple community locations.
Parasite Monitoring.
Parasites are a natural part of aquatic ecosystems, but documenting which parasites are present, how common they are, and how parasite communities change can provide valuable information about salmon health.
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The project examines gastrointestinal samples to measure parasite burden and uses molecular methods such as qPCR to help identify parasite species. Combining parasite information with other biological samples allows researchers to investigate broader patterns in salmon condition.
Common Parasites.
Anisakids
Anisakids are parasitic roundworms commonly found in wild marine fish, including salmon. They may appear as small, tightly coiled worms in or around the internal organs and occasionally in the flesh.
Their presence is a normal part of the marine food web. Salmon become infected by eating prey that carry the parasite, and the parasite can then be passed to marine mammals when infected fish are eaten.
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Seeing an anisakid does not automatically mean the entire fish needs to be discarded. Proper handling and preparation are important when consuming wild salmon, particularly if it will be eaten raw or undercooked.
Ichthyophonus.
Ichthyophonus has received increased attention in Alaska because infections have been investigated as one potential factor affecting the health and survival of Chinook salmon returning to the Yukon River. The parasite can damage internal tissues, including the heart, and severe infections may reduce a salmon’s ability to successfully complete its long freshwater migration.
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Copper River salmon and Yukon River salmon return to different watersheds, but they share portions of the North Pacific Ocean during their marine life and can encounter similar food sources, environmental conditions, and potential disease or parasite exposure. Finding Ichthyophonus in another Alaska salmon population therefore raises important questions about where exposure occurs and whether similar patterns could emerge elsewhere.
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AITRC’s goal is to be proactive rather than reactive. By monitoring Copper River sockeye and Chinook salmon now, we can establish baseline information about how common Ichthyophonus is in our fish and track changes over time. If prevalence or severity begins to increase, having years of baseline data will help us recognize those changes early and better understand what they may mean for Copper River salmon.
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Current results are encouraging: detectable Ichthyophonus infection has been very low in the Copper River salmon sampled, but continued surveillance helps ensure we are watching for changes rather than waiting until there is a larger concern.
What is Histology/Histopathology?
Histology is the process of preparing tissue so it can be examined under a microscope. Tissue samples are preserved in formalin, processed, cut into very thin sections, and stained so the structures within the tissue can be seen clearly.
Histopathology is the examination of those tissues for changes associated with disease. By looking closely at the cells and tissue structure, researchers can identify abnormalities such as inflammation, tissue damage, parasites, or other signs of infection or disease.
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For our salmon health monitoring, histopathology allows us to see changes inside organs that may not be visible from the outside of the fish and compare tissues from fish that appear healthy with those showing signs of disease.
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2024 Fisheries Technician, Bailey Roberts, measures the length of a salmon while taking health samples.
Ecologist, Kelsey Stanbro, and 2023 Fisheries Technician, Mia Bobowski, collecting health samples.
Bella Ranck, 2025 Fisheries Technician, joined Kelsey Stanbro, AITRC’s Ecologist, and Morag Clinton, Veterinary Pathologist, for salmon health sample training!
2024 Fisheries Technician, Luke Duvall, taking health samples of the GI tract.
Anecdotal reports of symptoms of this pathogen from Tribal Citizens have been an important motivator for the project. Given that Ichthyophonus is suspected as a potential contributor to the declining Yukon salmon (In 2021, 44% of Chinook salmon returning to the Yukon to spawn were infected with Ichthyophonus, which was higher than in previous years. In 2022, preliminary results from testing 2022 Chinook indicated a high prevalence of Ichthyophonus at around 40%.) returns, proactive monitoring of Copper River sockeye and Chinook salmon is essential. In 2023, AITRC collected 148 samples to analyze parasite burden and Ichthyophonus presence, and 75 cultures (64 sockeyes and 11 Chinook salmon) were sent to the ADFG Pathology Laboratory for testing. One sample returned a positive result for Ichthyophonus, but due to contamination—a common issue during field sampling—it cannot be confirmed with 100% certainty. Samples were collected for both culture and histology. At this time, none of the 2022 histology samples showed signs of Ichthyophonus. However, the histology of the 2023 samples revealed inflammation lesions and myocyte cell death in some samples. Inflammation and myocyte cell death in salmon hearts are signs of stress and disease that could significantly impair their survival and reproductive success. It's essential to investigate the underlying causes to understand their potential impact on fish populations and food security. In 2024, AITRC partnered with ADFG Pathology Lab and Sitka Sound Science Center on this project and expanded the sampling scope to include kidney, heart, and spleen from Chinook and sockeye salmon. This more holistic approach utilized both PCR and histology to examine different diseases. This more holistic approach should provide deeper insights into disease dynamics in Copper River salmon. There are currently no results.
Project Leads: Kelsey Stanbro | Questions on this project?