Session E5: Salmon Fishways in the Columbia River Basin and their Use by White Sturgeon

Abstract: The Columbia River Basin is the most dammed river system in North America. Home to five species of anadromous Pacific salmon, the nine mainstem dams on the Columbia River and four on the Snake River were constructed with fishways to enable salmon to return upstream to natal spawning areas. Most of these dams were constructed with two fishways; one adjacent to each riverbank. The fishways have overflow weirs with submerged orifices and some vertical slot structures. Fish lifts constructed at Bonneville Dam in the 1940s were used to pass white sturgeon upstream but their use was discontinued in the 1950s because the lifts were ineffective for passing adult salmon. Fish counting stations were constructed in all fishways. White sturgeon, a resident migratory species native to the Columbia Basin, was not mandated to be counted until 2006 despite knowledge of their presence in fishways dating back to the 1940s. However, due to their charismatic appearance and relative scarcity in fishways, the people counting the fish voluntarily enumerated them and often estimated their size and noted direction of movement within the fishways. Daily passage of white sturgeon from 1998 through present are now available in digital format and I used the data to address specific questions regarding upstream passage by white sturgeon. Mean lengths and peak of timing of white sturgeon counted suggests that current upstream passage is not related to a spawning migration. Differences in white sturgeon lengths and differences in timing of counts between fishways at individual dams suggest that physical or hydraulic conditions influencing approach, attraction, entry, and ultimately passage differ among sites. These findings suggest that further study could provide information on ways to improve upstream passage of white sturgeon.
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