Spatial and temporal variation in toadfish (Opsanus tau) and cusk eel (Ophidion marginatum) mating choruses in eelgrass (Zostera marina) beds in a shallow, temperate estuary

Passive acoustic recordings were made at two sites over a four-month period in eelgrass beds in a shallow estuary (Shinnecock Bay, New York, USA). Recordings were dominated by mating calls of striped cusk eels (Ophidion marginatum) at one site, and oyster toadfish (Opsanus tau) mating calls at the other. Cusk eel call characteristics (frequency and pulse period) varied significantly with time and water temperature. Fundamental frequency of toadfish calls decreased over the recording period and was not correlated with water temperature. We developed and tested automated detection algorithms to identify choruses using band-limited sound pressure levels. Distinct diel peaks in sound production were observed, with cusk eels producing morning and evening choruses, and toadfish calling mostly during daytime. Several physical and environmental variables were significantly correlated with the presence of cusk eel and toadfish choruses such as water temperature, tide state, and moon phase. The temporal variation in sound production and call characteristics differed from other studies, suggesting geographical variations in the acoustic behaviour of both species. Passive acoustic techniques can identify the location and timing of reproductive events for cryptic species that live in shallow water (<2 m) habitats, which are critical information for identification of their habitat.