Abstract

Many species of marine fishes produce species-specific sounds associated with reproductive behaviors. Passive acoustic monitoring has been used to study groupers that produce courtship associated sounds (CAS) when they aggregate to spawn. This technique has revealed patterns of sound production during spawning aggregations with extremely high temporal resolution. A primary goal to continue to expand the application of passive acoustics is to measure trends in abundance over time and apply this to spawning stock or population estimates during critical life stages. Underwater visual census has been most commonly used to estimate fish abundances during aggregations, but with several limitations (i.e. weather constraints, depth, fish behavior, water quality) that restrict its long-term effectiveness. A factor that limits the extrapolation of CAS counts to fish abundance is knowing the call rate of an individual fish. Groupers have a sound production mechanism made up of cranial muscles vibrating onto the swimbladder and generating sound waves. During the 2017 spawning season, red hind (Epinephelus guttatus) where held in a 1,500-gallon tank with an accelerometer tag and a low frequency hydrophone to record CAS. By placing the accelerometer tags near the fish the vibrations generated during sound production were detected, and correlated with CAS. In additional experiments, stronger signals of induced alarm calls produced by red hind were simultaneously recorded by both methods, confirming the potential of this approach to make passive acoustic monitoring useful for assessing spawning aggregations of groupers

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