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Inventory of Harvestable Subsistence Fish in Lakes within WRST
Many lakes within Wrangell–St. Elias National Park and Preserve support populations of resident fish that have long provided food for local communities. Despite their importance, relatively little is known about the abundance, size, and distribution of these fish populations.
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In partnership with the National Park Service, AITRC is conducting a multi-year inventory of harvestable subsistence fish in remote lakes throughout the park. The project provides baseline information that will help improve our understanding of these fisheries and support future monitoring and resource management.
Why Sonar?
Unlike traditional counting methods, sonar uses high-frequency sound waves to produce video-like images of fish moving through the river. This allows fish to be counted day and night, regardless of water clarity, while minimizing disturbance to migrating salmon.
However, the success of sonar depends heavily on the shape of the river channel. The river bottom must provide a clear viewing area so fish cannot pass unseen beneath or behind underwater features.
Why this spot?
The first phase of this project focused on identifying suitable sonar locations downstream of the Richardson Highway Bridge.
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Bathymetric surveys were conducted to map the river bottom and evaluate channel depth, slope, and substrate. Suitable bathymetry is critical for accurate fish passage estimates, as uneven bottoms, large boulders, or deep holes can create sonar shadows where fish may pass undetected.
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The surveys identified several potential monitoring locations with channel characteristics that could support reliable sonar operation.
Why Bathymetry Matters?
A smooth, well-defined river bottom allows the sonar beam to fully image the river channel. Large rocks, steep drop-offs, or other obstructions can block the sonar signal, creating hidden areas where fish cannot be detected.
These blind spots can result in undercounting fish if site conditions are not carefully evaluated before deployment.
Building Future Monitoring Capacity.
This pilot study represents an important step toward expanding fisheries monitoring in the Gulkana River. If successful, a permanent sonar station could provide continuous estimates of salmon escapement, improving fisheries management while supporting Tribal stewardship and long-term conservation of one of the Copper River Basin's most important salmon-producing rivers.
Through collaboration between AITRC and ADF&G, this project combines modern fisheries technology with long-term monitoring efforts to improve our understanding of salmon populations in the Ahtna Territory.
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.