Characterizing coastal cod vocalization using a towed hydrophone array

Abstract To better understand spawning vocalizations of Norwegian coastal cod (Gadus morhua), a prototype eight-element coherent hydrophone array was deployed in stationary vertical and towed horizontal modes to monitor sounds during an experiment spring 2019. Depth distribution aggregations monitored concurrently with ultrasonic echosounder. Cod recorded on the are analysed provide time–frequency characteristics, source level after correcting for one-way transmission losses from locations array. The vocalization frequencies range ∼20 600 Hz peak power frequency ∼60 Hz, average duration 300 ms, mean 163.5 ± 7.9 dB re 1 μPa at m. Spatial dependence received rates is estimated using measurements as horizontally deeper surrounding waters shallow water inlet areas experimental site. bathymetric-dependent probability detection regions quantified found be significantly reduced shallow-water inlet. We show that towable moving vessel invaluable because it can survey activity multiple locations, providing continuous spatial coverage complementary fixed sensor systems temporal given location.