Seasonal Dynamics and Environmental Drivers of Goliath Grouper (Epinephelus itajara) Sound Production

The Goliath groupers are known to produce characteristic low frequency vocalizations (calls) during spawning aggregations and as part of territorial behavior. Acoustic monitoring for Goliath grouper calls around Florida has historically occurred between July and December to capture the spawning season, with a particular focus on August-November. Because of the unique waveform of the Goliath grouper call, we implemented a noise adaptive matched filter to automatically detect Goliath grouper calls from year-round passive acoustic recordings at two wrecks off Florida's Gulf of Mexico coast. We investigated diel, temporal and environmental factors that could influence call rates throughout the year. Call rates peaked in August, around 0300 EST and just after the full moon. The Goliath groupers were more vocal when background noise was between 70 and 110 dB re 1 & mu;Pa. An additional smaller peak in call rates was identified in May, outside of the typical recording period, suggesting there may be other stimuli besides spawning that are eliciting high sound production in this species. Goliath grouper sound production was present year-round, indicative of consistent communication between individuals outside the spawning season.

Automated summary

The Goliath groupers are known for their characteristic low frequency vocalizations during spawning aggregations and territorial behavior. A noise adaptive matched filter was used to automatically detect Goliath grouper calls from year-round passive acoustic recordings. Call rates were highest in August, around 0300 EST and just after the full moon, and when background noise was between 70 and 110 dB re 1 μPa. A smaller peak in call rates was also observed in May, suggesting other stimuli besides spawning may elicit high sound production in this species.