Sound is everywhere in the marine environment and hearing is therefore a very important for stimuli for fish. They use sound for orientation and communication, during migration, aggregation and... Show moreSound is everywhere in the marine environment and hearing is therefore a very important for stimuli for fish. They use sound for orientation and communication, during migration, aggregation and spawning, but also for detection of prey and predators. Understanding how fish are effected by sound has become increasingly important in light of the increasing contribution of noise produced by human activity at sea. In this thesis, I investigated the effects of two anthropogenic sound sources in relation to the movement behaviour of free-swimming Atlantic cod (Gadus morhua) in the North Sea: seismic surveying for the exploration of the seabed and pile driving during the construction of offshore windfarms. Results from the two sound exposure studies demonstrated that both seismic and piling sound effect the behaviour of cod. Exposure to a seismic survey resulted in reduced activity during exposure and fish leaving the area earlier in the year. Piling did not result in leaving but did cause cod to move closer to the hard bottom structures. Ultimately, these insights will bring us one step closer towards recognising the effects of anthropogenic noise on the behaviour of individual marine fish and the potential consequences this may have at population level. Show less
Knaap, I.E.J. van der; Slabbekoorn, H.W.; Moens, T.; Eynde, D. van den; Reubens, J. 2022
Geophysical exploration of the seabed is typically done through seismic surveys, using airgun arrays that produce intense, low-frequency-sound pulses1 that can be heard over hundreds of square... Show moreGeophysical exploration of the seabed is typically done through seismic surveys, using airgun arrays that produce intense, low-frequency-sound pulses1 that can be heard over hundreds of square kilometers, 24/7.2,3 Little is known about the effects of these sounds on free-ranging fish behavior.4, 5, 6 Effects reported range from subtle individual change in activity and swimming depth for captive fish7,8 to potential avoidance9 and changes in swimming velocity and diurnal activity patterns for free-swimming animals.10 However, the extent and duration of behavioral responses to seismic surveys remain largely unexplored for most fish species.4 In this study, we investigated the effect of a full-scale seismic survey on the movement behavior of free-swimming Atlantic cod (Gadus morhua). We found that cod did not leave the detection area more than expected during the experimental survey but that they left more quickly from 2 days to 2 weeks after the survey. Furthermore, during the exposure, cod decreased their activity, with time spent being “locally active” (moving small distances, showing high body acceleration) becoming shorter, and time spent being “inactive” (moving small distances, having low body acceleration) becoming longer. Additionally, diurnal activity cycles were disrupted with lower locally active peaks at dusk and dawn, periods when cod are known to actively feed.11,12 The combined effects of delayed deterrence and activity disruption indicate the potential for seismic surveys to affect energy budgets and to ultimately lead to population-level consequences.13Show less
