|Document Type:||Journal Article|
|Title:||Evidence for fluoride effects on salmon passage at John Day Dam, Columbia River, 1982-1986|
|Author:||David M. Damkaer, Douglas B. Dey|
|Journal:||North American Journal of Fisheries Management|
There is evidence that fluoride from an aluminum plant near John Day Dam had a significant negative effect on passage time and survival of adult Pacific salmon Oncorhynchus spp. at the dam. In 1982, fluoride concentrations of 0.3-0.5 mg/L were recorded at the dam. These concentrations were probably representative of fluoride levels at the dam in earlier years as well, based on the aluminum plant's fluoride discharge records since 1971. From 1980 to 1982, the time (> 150 h) required for upstream migrants to pass John Day Dam and the mortality (>50%) of migrants between Bonneville and McNary Dam (below and above John Day Dam) were unacceptably high. Bioassay experiments on the behavior of upstream-migrating adult salmon suggested that fluoride concentrations of about 0.5 mg/L would adversely affect migration. Subsequent experiments suggested that 0.2 mg F/L was at or below the threshold for fluoride sensitivity of Chinook salmon O. tshawytscha and below the threshold for fluoride sensitivity of coho salmon O. kisutch. Beginning in 1983 and continuing through 1986, fluoride discharges from the aluminum plant were greatly reduced, and there was a corresponding drop in fluoride concentrations in the river. Concurrently, fish passage delays and inter-dam losses of adult salmon decreased to acceptable levels (28 h and < 5%, respectively).