Alewifes avoid high frequency sound
alewife, high frequency, sound, power plant, intake, sound pressure levels, night, swimming
Journal or Book Title
North American Journal of Fisheries Management
The authors studied the response of the alewife (Alosa pseudoharengus) to high-frequency sound to develop an acoustic system for preventing fish from entering power plant intakes. Four groups of alewives were subjected to different frequencies of sounds ranging from110 to 150 kHz at sound pressure levels (SPLs, given in decibels (dB) in reference to 1 mu Pa)ranging from 125 to 180 dB. Each group of 20 or 25 fish was tested in a cage that was suspended in a flooded rock quarry. During the day, alewives schooled and strongly avoided pulsed tones (500 ms pulses, 1,000 ms apart) of 110 and 125 kHz at or above 175 dB, a continuous tone of 125 kHz at 172 dB, and pulsed broadband sound between 117 and 133 kHz at or above 157 dB. Although alewives habituated to tones, they avoided pulsed broadband sound at 163 dB more consistently. The more consistent response to the broadband sound was probably due to the range of frequencies in this signal. At night, alewives did not school, did not swim actively, and did not react as strongly to the broadband sound. The diminished avoidance response at night may be due to the absence of schooling and to reduced swimming activity.