COMPARISON OF HYDROACOUSTIC AND NET CATCH ESTIMATES OF PACIFIC SALMONSMOLT (ONCORHYNCHUS SPP) PASSAGE AT HYDROPOWER DAMS IN THE COLUMBIA RIVER BASIN, USA

In the last 16 years, fisheries agencies and power producers in the Co lumbia River Basin have increasingly relied on hydroacoustic assessmen ts of downstream migrating, anadromous Pacific salmon smelts (Oncorhyn chus spp.) when evaluating bypass system designs at hydroelectric dams . Accompanying this reliance has been an interest in comparing hydroac oustic estimates of smelt passage with net catch estimates. Since the objectives could be addressed effectively with relative estimates of f ish passage, single-beam hydroacoustic techniques were used. The corre lation between hydroacoustic and net catch estimates of smelt 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 c orrelation between net catch estimates and hydroacoustic estimates of smelt passage was statistically significant (r=0.96, n=21, p<0.001). A t Wanapum Dam, in 1994, there was a significant correlation between ne t catch and hydroacoustic estimates of smelt 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 corre lation between mean hydroacoustic and net catch estimates of in-turbin e diversion screen fish guidance efficiency (r=0.36, n=37, p=0.031), w ith no significant difference between the paired estimates. (C) 1996 I nternational Council for the Exploration of the Sea.