Assessment of cumulative sound exposure level as criterion for exposure of fish to impulsive sound

Acceptable exposure of fish to pile driving impulsive sound is currently determined by cumulative sound exposure level (SEL). The implicit assumption in this regulatory approach is that cumulative SEL, regardless of how reached, is one of the critical measures of sound exposure for fish health. We are testing this assumption by exposing juvenile Chinook salmon to sequences of impulsive sound differing in individual impulse SEL and number of impulses, but with the same cumulative SEL value. Test fish are exposed in a unique device that permits accurate simulative of impulsive pile driving sound. Following exposure, the hearing of test fish is evaluated using auditory evoked potential methods followed by necropsy for assessment of barotrauma. The null hypotheses we are testing is that the probability of hearing threshold shift ⩾6 dB and the probability of barotrauma mortal injury is the same for all cumulative SEL exposures. The results of these tests will determine the experimental design of additional tests to derive criteria for exposure of fish to pile driving sound. [Work supported by National Cooperative Highway Research Program (NCHRP) and Minerals Management Service (MMS).]