Drivers of male sound production and effective communication distances at fish spawning aggregation sites

Abstract

Abstract While monitoring fish sounds has enhanced our understanding of spatio-temporal patterns of spawning and acoustic communication, data interpretation often fails to account for environmental effects on acoustic recordings, resulting in uncertainty of whether measures of detected fish sounds correspond to rates of sound production, specific behaviours, and abundance. In this study, we applied acoustic propagation modelling and detection theory to estimate rates of sound production of territorial, male Gulf grouper (Mycteroperca jordani) from passive acoustic recordings and evaluate effective communication distances. To assess behavioural drivers, environmentally calibrated, hourly estimates of sound production rates were compared to diver observations of courtship, spawning, and numbers of females encountered within male territories. Rates of sound production increased before sunset and were correlated to observed rates of spawning and females encountered, indicating that sound production is largely driven by female presence and increased opportunities to spawn. The mean effective communication distance was estimated to be <21 m, supporting the importance of short-range communication within the observed behaviours. Our findings corroborate that fish sounds can be used to infer measures of reproductive activity and the relative abundance of both sexes during spawning periods once properly calibrated for environmental effects and detection capabilities.