Recurring fish losses at power plant cooling-water intakes demonstrate the need for improving intake design and operation to reduce the impact on aquatic resources. An approach is proposed for deriving intake velocity criteria which focuses on the interaction of bioenergetics and fish behavior. A model based on an energetic optimum and selected swimming speed is used to predict the response of fish to hydraulic flow fields. Data on oxygen consumption rates for juvenile chinook salmon (Oncorhynchus tshawytscha) indicate maximum energetic efficiency occurs at a swimming speed of 25 cm/sec. Juvenile chinook salmon exposed to a velocity gradient behaviorally select a velocity of approximately 21 cm/sec. These results support the basic hypothesis that the behavioral response of fish to a hydraulic flow field is not random but is predictable in terms of an energetically optimal swimming speed for a given species and size class. Physical and biological factors which influence predictions of the model are described. Applications of the model in understanding fish response to water intakes are suggested. Limitations of this approach in establishing power plant intake design criteria are also discussed.
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