Immediate and delayed (96 h) mortality, descaling, and injury rates of striped bass Morone sax‐atilis and rainbow trout Oncorhynchus mykiss that were inserted into the entrance (suction side) of a Hidrostal pump were compared to those of control fish that were inserted at the exit (pressure side). Comparisons were made in 158‐paired trials of striped bass and 86 trials with rainbow trout. The Hidrostal pump had no significant effect on immediate or delayed (96 h) mortality. Immediate mortality for striped bass and rainbow trout averaged 0.1 and 0%, respectively, and delayed mortality averaged 2.9 and 0.1%, respectively. Mean scale loss after passage for striped bass and rainbow trout was low (0.2 and 1.0%, respectively). Frequency of injury to the head, eyes, skin, and tins of pumped striped bass averaged 1.9, 2.8, 1.9, and 18.7%, respectively, and those of rainbow trout averaged 2.3, 0, 2.4, and 3.1%. No significant relationships were detected between fish mortality and pump speed, injected fish density, and debris load. Results suggest that large Hidrostal pumps have the capacity to transport live striped bass and rainbow trout at high density (1‐6 fish/L) with little mortality and body injury.

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