An empirically derived age-, time-, and space-variant equation was used to estimateentrainment mortality at power plants for seven fish species inhabiting the Hudson River estuary.Entrainment mortality is expressed as a conditional rate, which is the fractional reduction in yearclassstrength due to entrainment if other sources of mortality are density-independent.Estimates of the conditional entrainment mortality, based on historical and projected oncethroughcooling operation of five power plants, were 11-22% for striped bass, 11-17% for whiteperch, 5-7% for Atlantic tomcod, 14-21% for American shad, 4-11% for river herring (alewife andblueback herring combined), and 35-79% for bay anchovy. Closed-cycle cooling (natural-draftcooling towers) at three of the power plants (Indian Point, Bowline Point, and Roseton) wouldreduce entrainment mortality of striped bass by 50-80%, of white perch by 75-80%, of Atlantictomcod by 75-70%, of American shad by 80%, or river herring by 30-90%, and of bay anchovy by45-80%. The life stages most vulnerable to entrainment mortality were post-yolk-sac larva andentrainable-size juvenile.