Response Persistence to Repeated Sound Exposure During a Tank Study in Pelagic Fish

Marine fish inhabit an acoustic world and are often exposed to anthropogenic noise. Natural sounds play an important role in spawning aggregations, finding prey, escaping predators and guiding spatial behavior. Noise pollution at sea includes the prominent presence of sounds from vessels, but also pile driving, seismic surveys, and explosions, which can cause extreme overexposure. Such extreme events can cause physical damage and even mortality for nearby fish. Acoustic Deterrent Devices, using sounds at moderate levels, may be used to scare fish away from dangerous sites. Investigation of acoustic responsiveness to deterrent sound stimuli is challenging at sea due to low-visibility and limitations of tagging studies, while captive studies yield high resolution data that can be used to compare sound treatments. In this study, eight pulse train variants were tested on captive Atlantic herring (Clupea harengus) and methodological steps for measuring 3D behavior automatically for groups of four fish are reported. Potential decay in responsiveness was tested at two levels: within the repetitive exposure of ten pulse trains during a treatment, and across eight treatments over 2 days. Upon sound onset, herring showed an immediate increase in turning behavior and swam deeper in the basin. There was no decay or change in any behavioral response at either level. The discussion explores the importance of response persistence within the context of responsiveness tests in captivity.