Comparison of Hydroacoustic and Net Estimates of Fish Guidance Efficiency of an Extended Submersible Bar Screen at John Day Dam

Abstract

Abstract We compared results of the hydroacoustic and netting methods of estimating guided and unguided fish passage and evaluated fish-guidance efficiency (FGE) of an extended submersible bar screen at John Day Dam on the Columbia River. Hydroacoustic counts of guided fish were significantly correlated with concurrent gatewell catches (r2 = 0.73; N = 39), as were hydroacoustic counts of unguided fish with fyke-net catches (r2 = 0.71; N = 39). However, hydroacoustic sampling significantly underestimated both guided and unguided fish passage relative to netting estimates. We could not explain the underestimates by modeling hydroacoustic detectability, and the distribution of fish passage across the intake width was not skewed away from transducer sampling volumes. Hydroacoustics provided relatively unbiased estimates of fish guidance efficiency (guided/(guided + unguided)) because of compensating errors in the numerator and denominator. The best correlation between net and hydroacoustic estimates of effici...