Survival and Injury of Splittail and Chinook Salmon Passed through a Large Hidrostal Pump

Abstract

The passage survival, descaling, and injury rates of marked splittail Pogonichthys macrolepidotus and juvenile chinook salmon Oncorhynchus tshawytscha that were inserted into the entrance (suction side) of a Hidrostal pump were compared with those of control fish inserted at the exit (pressure side) in 130 paired trials conducted from December 1998 to July 1999. The Hidrostal pump had no significant effect (P < 0.001) on immediate or latent (96-h) mortality, descaling, or body injury rates for all flow rates and sizes and densities of fish tested, except for the 96-h mortality of splittail in June. The immediate survival rates for splittail and chinook salmon averaged 99%, and the cumulative (96-h) survival for these species averaged 93% and 96%, respectively. Average scale loss on splittail and chinook salmon usually was low (1.9% and 2.4%, respectively), and the frequency of injury to head, eyes, skin, and fins typically was low and not significantly different among quality control, control, and treatment fish. Observations on wild fish (26 species; 7,197 fish) entrained from the Sacramento–San Joaquin River Delta during the pumping trials indicated high immediate survival (99%). The Hidrostal pump transported a variety of sizes and numbers of native fishes with low mortality and injury rates over a range of pump velocities and environmental conditions. Hidrostal pumps that can safely transport fish screened from a water diversion canal through a bypass return to a river may have important fisheries management applications.