Bull Trout (Salvelinus confluentus) were once widely distributed in the Upper Willamette Basin. Construction of large flood control and hydroelectric dams in the mid-twentieth century, including Cougar, Trail Bridge, Lookout Point, and Hills Creek dams, fragmented habitat and blocked migration between spawning and rearing areas. By the 1990s, Bull Trout had been extirpated from the Santiam basins and the Middle Fork Willamette, and only three small spawning populations remained in the McKenzie River drainage. Bull Trout were listed as threatened under the federal Endangered Species Act in 1998.
Native Fish Investigations, in partnership with ODFW District Staff, the U.S. Fish and Wildlife Service, U.S. Army Corps of Engineers, U.S. Forest Service, and others, works to maintain and recover Bull Trout populations across the Upper Willamette through a combination of active management, reintroduction, and long-term monitoring. Because several dams in the basin still lack adequate fish passage, project staff assist with passage of adults collected at the Cougar Dam fish passage facility and have also worked to pass Bull Trout upstream at Hills Creek Dam. We have also translocated juvenile Bull Trout from healthy source populations to reintroduction sites in the Middle Fork Willamette. To track the status and trajectory of these efforts, we conduct annual spawning surveys, juvenile snorkel surveys, and PIT tag monitoring across both basins, and facilitate genetic sampling to assess population structure and connectivity. We are also working with partners to assess the feasibility of reintroducing Bull Trout to the North Santiam River basin, where the species was historically present.
In 2023, spawning surveys documented 235 redds across the Upper Willamette Basin, continuing a long-term positive trend. In the Middle Fork Willamette, where Bull Trout were considered functionally extinct in the late 1990s, redd counts have risen steadily and reached a record high in 2023. Preliminary data from 2025 suggest redd counts have declined, though the extent and significance of this change are still being evaluated.