Assessing population effects from entrainment of fish at a large volume water intake

Abstract

Industrial, municipal, and agricultural activities require large volumes of water that are generally obtained from lakes, reservoirs, rivers or oceans through intake systems that may also effect aquatic and marine organisms. Quantifying these effects is often difficult and may require innovative methods. We describe a method for estimating population effects from entrainment of juvenile chinook salmon (Oncorhynchus tshawytscha) at a steam electric generating station on the Columbia River that required cooperation between power plant operators and fishery biologists. The method involved sampling fish in the river and entrained fish (both marked recaptures and naturally occurring downstream migrants) within the intake, and estimating the 1) total number of fish entrained, 2) size of the natural population, and 3) percent of the natural population affected.