Red hind Epinephelus guttatus vocal repertoire characterization, temporal patterns and call detection with micro accelerometers

Abstract

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 red hind (Epinephelus guttatus) spawning aggregations with extremely high temporal resolution. In particular, it has been shown that groupers can have a varied vocal repertoire, however, detailed studies of the number, types and periodicity of CAS are lacking. The purpose of this study was to characterize and understand in detail the CAS and other vocalizations in E. guttatus and their respective behavioral context, using a combination of field and laboratory studies. During the 2017 spawning season (Dec – Feb), red hind where held in a 57,000-liter tank equipped with a low frequency acoustic recorder and video cameras to record behavior. Additionally, the experimental set up included an open accelerometer to detect sound in smaller devices, which can enable scientist to track individual fish vocalizations in the field. Field recordings from a simultaneous spawning aggregation were used to quantitatively characterize and compare the sound types recorded by audio and video during captivity. Five sound types were characterized: four from captivity and an additional one from the field recordings - ‘chorus’. These sounds consisted of variations and combinations of low (50-450hz) pulses, Grunt/Grunt Trains and tones. Some vocalizations exhibited diel and lunar oscillations, and for these both field and captivity recordings peaked daily at 1800 AST and at 8 days after the full moon. The open accelerometer was successful in recording sound but only at minimal range. Standardizing characterization of call types, coupled with this improved technology will facilitate automating call detections. Such improved data will further help relate call types to behavior, test hypotheses relating calling behavior to fitness and mate choice, determine the existence of regional dialects (indicating connectivity within the Caribbean) and assist management in monitoring and assessing grouper aggregations. This research was accepted for review by the Journal of Fish Biology.