Sound production of red grouper Epinephelus morio on the West Florida Shelf

Passive acoustic and digital video recordings were used to investigate sonic activity and behavior of red grouper Epinephelus morio on the West Florida Shelf. Red grouper were found to produce a unique series of low-frequency (180 Hz peak) pulses consisting of 1 to 4 brief (0.15 s) broadband pulses and a 0.5 to 2 s growl (short call); occasionally these were followed by a rapid series of 10 to 50 broadband pulses (pulse train). Sound production was ob served throughout the day and night, but most sounds occurred between sunrise and sunset, with a noticeable increase during late afternoon. Behaviors asso ciated with sound production included solitary male activity and court ship interactions, indicating that sound production is likely related to spawning activity. Thus, passive acoustics could be an effective tool in monitoring red grouper reproduction and defining critical habitat of a keystone species.