Effect of spill on adult salmon passage delay at Columbia River and Snake River dams
نویسندگان
چکیده
Spill, used to assist the downstream passage of juvenile Chinook salmon (Oncorhynchus tshawytscha), and steelhead (O. mykiss) at eight dams in the Columbia/Snake River hydrosystem may delay the upstream passage of the adults. To evaluate the potential effects of spill on adult passage we evaluated the historical relationship between the day-to-day variations of spill and upstream fish passage at the eight dams of the Columbia/Snake river hydrosystem between 1960 and 2010. Seven of the dams had negative relationships in which an increase in spill was statistically correlated with a decrease in passage. The Dalles Dam, which has a unique configuration of spill bays, powerhouses and adult passage facilities, had a significant positive relationship. Steelhead salmon were most sensitive to changes in spill throughout the system, and jack Chinook, the least sensitive. These patterns suggest that the spill-passage relationship is weak but depends on both migration behavior and dam configuration. In general, the analysis indicates that spilling 30% of the river flows to assist juvenile fish downstream passage delays the adult upstream passage by about one day on a total hydrosystem passage of between two and four weeks depending on species.
منابع مشابه
Influence of river conditions during seaward migration and ocean conditions on survival rates of Snake River Chinook salmon and steelhead
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