Testing acoustic fish deterrents for use under-ice in arctic lakes

Abstract

Acoustic deterrent technologies can be used in aquatic settings in lieu of physical barriers to keep fish away from potentially harmful industrial operations. The goal of this study was to determine the efficacy of portable, temporary acoustic deterrents as a means of excluding fish from the neighborhood of sub-bottom detonation activities associated with seismic exploration under ice in arctic lakes. In October 2003 trials were conducted in Dolomite Lake near Inuvik, Northwest Territories, Canada on indigenous fish species. Groups of fish were equipped with orally inserted ultrasonic tags, placed in a large experimental net pen and monitored using an acoustic tracking system that produced a detailed three-dimensional swimming pattern for each subject, thereby revealing any behavioral responses. A flex-tensional broadband sound projector driven by digitally synthesized signals was tested as deterrent, and real-time monitoring at two hydrophone sites was used to estimate the local level of insonification throughout the pen volume. Although the study did not identify an overall effective deterrent, sufficient indications of response were observed to support the future testing of a louder projector capable of emitting a tonally modulated sound pattern at frequencies from about 100 Hz to a few kHz. [Work supported by ESRF (esrfunds.org).]