Effects of pressure changes induced by commercial navigation traffic on mortality of fish early life stages

Mortality of fish early life stages was measured in a pressure vessel to simulate vertical displacement within the water column. Mortality was measured for three pressure regimes for four fish species: larval bigmouth buffalo Ictiobus cyprinellus, larval blue catfish Ictalurus furcatus, juvenile bluegill Lepomis macrochirus, and juvenile largemouth bass Micropterus salmoides. The maximum pressure‐change tested, 344.8 kPa, equivalent to a 35.2 m displacement of fish within the water column, did not cause significant mortality of larvae or juveniles. Since 32.5 m exceeds depths in most inland navigation channels and possibly the depth to which rapid propeller induced water mixing occurs, the range of pressure changes that could be experienced by early life stages during towboat mixing of the water column will not result in significant mortality.