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Fish Health
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.
Noticing anything about the runs? Let us know at our In-Season Copper River Salmon Teleconfrences!
If you're fishing and don’t mind us collecting a sample or two, please reach out!​
Call or text our fish techs 907-259-3295!
GENETIC SAMPLES.
We use fin clippings to evaluate the effectiveness of in-season genetic stock identification (GSI) as a management tool for fisheries. By collecting small tissue samples from the fins of fish (fin clippings), we can extract DNA and determine which population or stock the fish originated from. This technique, known as genetic stock identification, allows us to monitor the composition of fish runs in real-time during the fishing season.
HEALTH SAMPLES.
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Heart
Spleen
Kidney
We use histology to compare the normal structure of the heart, spleen, and kidney to those from fish that appear diseased. Histology involves looking at thin slices of these organs under a microscope to identify signs of infection, inflammation, or tissue damage.
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This allows us to detect subtle changes in tissue that may indicate disease, even when symptoms aren’t visible externally. By comparing healthy and unhealthy fish, we can begin to understand how different diseases affect the body and potentially trace them back to their causes.
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We also use PCR (polymerase chain reaction) testing, a molecular tool that can detect the presence of pathogens—such as viruses, bacteria, or parasites—even when they are present in extremely small amounts.
This is especially useful for early detection, before the disease becomes widespread or starts causing obvious symptoms. Together, histology and PCR give us both a broad and precise picture of fish health, helping us monitor the spread of disease and protect fish populations.
Scales
We use fish scales to estimate age by examining growth rings, known as annuli—similar to how the rings of a tree can reveal its age. As fish grow, their scales grow too, forming concentric rings. Each year, a fish’s growth slows during winter and speeds up in summer, creating visible differences between fast and slow growth that show up as rings under a microscope. These rings—called annuli—can be counted to estimate the fish’s age.
GI Tract
The GI tract is one of the most common places for parasites to inhabit in fish. By carefully dissecting and inspecting the stomach and intestines, we can count how many parasites are present (parasite burden) and determine which species they are through microscopic examination or genetic testing.
Understanding parasite presence and diversity helps us monitor fish health and detect patterns over time—such as changes in parasite load across seasons, locations, or years. It can also help us assess how environmental conditions or migration patterns may influence parasite exposure in Copper River salmon
Blood
We collect blood samples from salmon to assess their overall health, detect the presence of pathogens, evaluate physiological condition, and study blood-borne parasites. By analyzing it, we can measure markers of stress, immune function, and organ performance. Blood tests can also help identify infections, including bacteria, viruses, and blood parasites that may not be visible through external examination. This information helps us monitor changes in salmon health over time and across different parts of the Copper River system, supporting efforts to manage and conserve the population.
Othilith
We sample otoliths, or “ear stones,” from fish to gather accurate information about their age, origin, and life history. Like tree rings, otoliths form annual growth layers that can be counted under a microscope, making them a reliable tool for determining a fish’s age—often more accurately than scales, especially in older or ocean-going fish.
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In hatchery-reared fish, otoliths may carry thermal marks created by controlled temperature changes during early development. These marks help identify the fish’s hatchery of origin and brood year, which is especially valuable in managing mixed-stock fisheries and distinguishing wild from hatchery fish.
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Additionally, the chemical composition of otoliths can reveal details about the environments a fish traveled through, such as transitions between freshwater and saltwater habitats.
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.