Native, resident fish will be collected below Ice Harbor Dam and Lower Granite Dam from April 3 to June 15 and below McNary and Bonneville dams from April 10 to June 21 each year from 2021 to 2025. Spatially, fish will be collected within 5 miles of each dam. Temporally, fish will be collected weekly below each dam during the spring spill period. Fish will be opportunistically collected from shallow-water habitat that can be effectively sampled with seines or backpack electrofishers. The target sample size will be 100 fish per week per dam, with a 50 fish minimum, that will comprise at least 3 species.

The following species will also be collected and transported to the USGS Columbia River Research Laboratory for testing in gas bubble trauma progression and mortality experiments: Three-spined stickleback, sculpin sp., northern pikeminnow, and larval lamprey. Stickleback will be collected downstream of Bonneville Dam or at Crims Island in the lower Columbia River with a beach seine. Sculpin sp. will be collected downstream of Bonneville Dam at Ives Island with a backpack electrofisher. Juvenile northern pikeminnow will be collected in Lower Granite Reservoir with a beach seine. Larval Pacific lamprey will be collected from silty tributary or side-channel habitats of the Columbia River. Approximately 1,000 fish of each species will be collected.