Sound from spawning cod at their spawning grounds

Abstract

Sound was recorded at five stations at and near the main spawning grounds of the northeast Arctic cod (Gadus morhua L.) off the Lofoten Islands, Norway. Recordings were carried out during April 1997 when large numbers of cod aggregated to spawn, and were repeated in September when the cod were no longer spawning and, in fact, most had emigrated. The analysis revealed differences between the two time periods with April showing sound of a transient character with 7-18 dB increased sound level between 50 and 500 Hz. Sound from single cod in captivity has been reported to be located in this frequency range. We argue that the sound recorded is produced by spawning cod and discuss acoustic communication as a potential mechanism in cod mate assessment.