Effects of water velocity and trash rack architecture on juvenile fish passage and interactions: A simulation

Publication Date



fish passage, juvenile, water velocity, migratory fish, ecosystems, fish screen, screens, louvers, diversion, pumps, trash racks, upstream, structures, survival, shad, chinook, salmon, bar spacing, spacing, tank

Journal or Book Title

Transactions of the American Fisheries Society


Many resident and migratory fish species have experienced population declines due tomodification of estuarine ecosystems. Fish screens (or louvers) have been designed to guide fishaway from the diversion pumps, and trash racks have been placed upstream of the screens tointercept aquatic plants and debris. Although small fish may aggregate around these structures,potentially increasing their vulnerability to predators, we know little about the behaviour,performance, and survival of fish near trash racks. To determine how trash rack flow regime andarchitecture influence fish behaviour, we exposed juvenile threadfin shad (Dorosoma petenense)and winter-run Chinook salmon (Oncorhynchus tshawytscha) to three water velocities and twobar spacing treatments in a circular tank bisected by a simulated trash rack. Our results suggestthat relatively small increases in water velocity at diversion facilities will result in the aggregationof juvenile fish near trash racks. In contrast, bar spacing did not influence fish passage frequencyor interaction in this study. We also found that threadfin shad selected higher velocities as watercurrent increased, whereas Chinook salmon consistently showed a preference for moderate tolow water velocities.





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