Title: Determination of Initial Inflation of the Swim Bladder and Vulnerability to Barotrauma in White Sturgeon (Acipenser transmontanus); Tools for Examining Susceptibility to Barotrauma in Larval Fish and Eggs

After hatching, larval sturgeon drift downstream with river flow and may drift hundreds of kilometers.  Therefore, in the Columbia River Basin, larval sturgeon may pass multiple hydroelectric dams potentially making them vulnerable to injuries associated with passage.  For example, fish passed through turbines commonly suffer from barotrauma as a result of rapid decompression.  Barotrauma has been strongly associated with expansion of gasses in the swim bladder of fish.  However, it is unknown at what life stage larval sturgeon fill their swim bladders, which would make them more susceptible to barotrauma.  The purpose of this investigation is to determine at what age larval sturgeon first fill their swim bladders with gas in an effort to assess vulnerability to barotrauma and enhance the survival of juveniles passed through turbines of hydroelectric dams.  Using hyper/hypobaric pressure chambers, larval and juvenile sturgeon of varying life stages will be exposed to pressure decreases.  With an inflated swim bladder, exposure to these pressure decreases will cause the fish to become positively buoyant and float upward.  Alternatively, if swim bladder inflation has not yet been developed, the fish will not become positively buoyant.  As an additional confirmation, x-ray examination of the fish for presence of gas bubbles in the swim bladder or other locations will be done to support our conclusions from the pressure testing.  Work of this nature has never before been conducted on developing sturgeon and results will improve current understanding of how larval and juvenile fish are affected by hydroturbine passage at dams.