Further Tests of Changes in Fish Escape Behavior Resulting from Sublethal Stresses Associated with Hydroelectric Turbine Passage
behavior, design, fish behavior, handling, hydroelectric, mortality, predation, rainbow trout, startle response, tank, trout, turbine passage, turbines, turbulence
None supplied. From summary: Fish that pass through a hydroelectric turbine may not be killed directly, but may nonetheless experience sublethal stresses that will increase their susceptibility to predators (indirect mortality). There is a need to develop reliable tests for indirect mortality so that the full consequences of passage through turbines (and other routes around a hydroelectric dam) can be assessed. The most commonly used laboratory technique for assessing susceptibility to predation is the predator preference test. In this report, we evaluate the field application of a new technique that may be valuable for assessing indirect mortality, based on changes in a behavioral response to a startling stimulus (akin to perceiving an approaching predator). Initial studies demonstrated that turbulence created in a small laboratory tank can alter escape behavior. As a next step, we converted our laboratory design to a more portable unit, transported it to Alden Research Laboratory in Holden, Massachusetts, and used it to test fish that passed uninjured through a pilot-scale turbine runner. Rainbow trout were either passed through the turbine or exposed to handling stresses,a nd their behavior was subsequently evaluated. We compared the behaviors of 70 fish passed through the turbine and another 70 under control conditions (either transferred from the holding tank or injected into the Alden loop downstream of turbine). The most immediate measure of potential changes in fish behavior was whether test and control fish exhibited a startle response. Unlike earlier studies, there was no significant difference among the treatment group and the controls for startle response. The majority of rainbow trout in all groups responded to the startle stimulus. There were, however, significant differences in some of the particular aspects of the subsequent escape behavior. The time to first reaction, the duration of the reaction, and the time associated with the maximum C-shape formation were all significantly different between the tank controls and the two groups of fish injected into the Alden turbine loop.