Identifying Sciaenid Critical Spawning Habitats by the Use of Passive Acoustics

Abstract Sounds produced by spawning fishes in Pamlico Sound, North Carolina, have been recorded both under captive conditions and in hydrophone and sonobuoy field surveys. These sounds, produced by males, are species specific, are associated with spawning, and are most likely used for advertisement to attract females. Sounds can be discriminated by use of spectral analysis (oscillograms and spectrograms) of recordings, and the peak frequencies produced by each species can be correlated with species and fish size. Sonobuoys were used for passive acoustic surveys, which were “sound truthed” from recordings of captive fishes to determine the timing and location of spawning sites for four species in the family Sciaenidae: Red drum Sciaenops ocellatus , spotted seatrout Cynoscion nebulosus , weakfish C. regalis , and silver perch Bairdiella chrysoura . During May‐September 1998, sounds were first detected in the early evening, increased in loudness after sunset, and ended by sunrise. Weakfish and silver perch were heard predominantly at inlet locations in May and June, whereas spotted seatrout (peak drumming in July) and red drum (peak drumming in September) were heard predominantly at lower‐salinity river mouth locations in western Pamlico Sound. Passive acoustic surveys can be used to determine critical spawning habitats of sciaenid fishes; such surveys have revealed interesting insights into fish behavior and should be integrated into ocean observing systems.