Comparison of hydroacoustic and net catch estimates of Pacific salmon smolt (Oncorhynchusspp.) passage at hydropower dams in the Columbia River Basin, USA

In the last 16 years, fisheries agencies and power producers in the Columbia River Basin have increasingly relied on hydroacoustic assessments of downstream migrating, anadromous Pacific salmon smolts (Oncorhynchus spp.) when evaluating bypass system designs at hydroelectric dams. Accompanying this reliance has been an interest in comparing hydroacoustic estimates of smolt passage with net catch estimates. Since the objectives could be addressed effectively with relative estimates of fish passage, single-beam hydroacoustic techniques were used. The correlation between hydro-acoustic and net catch estimates of smolt passage into the sluiceway at Ice Harbor Dam was statistically significant (r=0.96, n=26, p<0.001). Rocky Reach Dam hydroacoustic and fyke net catch vertical distributions were very similar. At Lower Granite Dam, the correlation between net catch estimates and hydroacoustic estimates of smolt passage was statistically significant (r=0.96, n=21, p<0.001). At Wanapum Dam, in 1994, there was a significant correlation between net catch and hydroacoustic estimates of smolt passage (r=0.96, n=10, p<0.001), and there was no statistically significant difference between the paired estimates. From 1991 to 1994, there was a significant correlation between mean hydroacoustic and net catch estimates of in-turbine diversion screen fish guidance efficiency (r=0.36, n=37, p=0.031), with no significant difference between the paired estimates.