Anthropogenic noise in the oceans is disturbing marine life. Among other groups, pelagic fish are likely to be affected by sound from human activities, but so far have received relatively little... Show moreAnthropogenic noise in the oceans is disturbing marine life. Among other groups, pelagic fish are likely to be affected by sound from human activities, but so far have received relatively little attention. Offshore wind farms have become numerous and will become even more abundant in the next decades. Wind farms can be interesting to pelagic fish due to food abundance or fisheries restrictions. At the same time, construction of wind farms involves high levels of anthropogenic noise, likely disturbing and/or deterring pelagic fish. Here, we investigated whether bottom-moored echosounders are a suitable tool for studying the effects of impulsive - intermittent, high-intensity - anthropogenic noise on pelagic fish around wind farms and we explored the possible nature of their responses. Three different wind farms along the Dutch and Belgian coast were examined, one with exposure to the passing by of an experimental seismic survey with a full-scale airgun array, one with pile driving activity in an adjacent wind farm construction site and one control site without exposure. Two bottom-moored echosounders were placed in each wind farm and recorded fish presence and behaviour before, during and after the exposures. The echosounders were successful in detecting variation in the number of fish schools and their behaviour. During the seismic survey exposure there were significantly fewer, but more cohesive, schools than before, whereas during pile driving fish swam shallower with more cohesive schools. However, the types and magnitudes of response patterns were also observed at the control site with no impulsive sound exposure. We therefore stress the need for thorough replication beyond single case studies, before we can conclude that impulsive sounds, from either seismic surveys or pile driving, are a disturbing factor for pelagic fish in otherwise attractive habitat around wind farms. Show less
In today's marine habitats, anthropogenic noise is widespread in space and time, affecting aquatic animalcommunities. Short-term exposure to noise is known to affect vital behaviours, such as the... Show moreIn today's marine habitats, anthropogenic noise is widespread in space and time, affecting aquatic animalcommunities. Short-term exposure to noise is known to affect vital behaviours, such as the ability toevade predators. However, long-term noise pollution may lead to differences in short-term responsesbetween naïve and experienced animals. We investigated the interaction between short-term and longterm sound exposure on the antipredator response of free-ranging sand gobies, Pomatoschistus minutus.We tested the effects of short-term boat noise playback on the response to a simulated predator strike inareas across a range of low to high long-term noise disturbance levels. Exposure to boat noise did notaffect the startle response, time frozen or response latency of gobies to a predator stimulus. However,individuals exposed to short-term boat noise playback were absent from the experimental area forshorter periods after the predator strike than gobies exposed to the silent control. Moreover, gobies inlong-term noisy habitats also stopped avoiding the area after the predator strike under silent controlconditions. These changes point to a decreased magnitude in antipredator response, as a function ofinteracting short- and longer-term levels of disturbance. Thus, prey species alter their antipredatorbehaviour in ways that can potentially lead to higher mortality for individual prey. This could ultimatelyhave implications at the level of the food web. Show less
The effects of anthropogenic noise on interactions between predators and their prey are still little understood. This thesis aims to fill pressing knowledge gaps on this topic by studying how... Show moreThe effects of anthropogenic noise on interactions between predators and their prey are still little understood. This thesis aims to fill pressing knowledge gaps on this topic by studying how anthropogenic noise affected various stages in the prey-hunting of predators and the predator-avoidance of prey. For predators, I investigated whether an¬thropogenic noise could influence habitat choice (chapters 2 and 3), foraging efficiency (chapter 3) and communication between foraging group members (chapter 4). For prey, I studied how anthropogenic noise affected prey behaviour outside of predation con¬texts (chapter 5) and if current and previous vessel noise exposure affected anti-predator behaviour when a simulated predator attacked (chapter 6). The multi-disciplinary studies of this thesis combine to unravel more insight into the influence of noise on predator-prey relationships in the marine environment. Further investigations should focus on revealing the mechanistic underpinning of noise effects on behaviour of both predator and prey. Only then will we be able to reduce the impact of noise on marine ecosystems. Show less
The continuing rise in underwater sound levels in the oceans leads to disturbance of marine life. It isthought that one of the main impacts of sound exposure is the alteration of foraging behaviour... Show moreThe continuing rise in underwater sound levels in the oceans leads to disturbance of marine life. It isthought that one of the main impacts of sound exposure is the alteration of foraging behaviour of marinespecies, for example by deterring animals from a prey location, or by distracting them while they aretrying to catch prey. So far, only limited knowledge is available on both mechanisms in the same species.The harbour porpoise (Phocoena phocoena) is a relatively small marine mammal that could quickly sufferfitness consequences from a reduction of foraging success. To investigate effects of anthropogenic soundon their foraging efficiency, we tested whether experimentally elevated sound levels would deter twocaptive harbour porpoises from a noisy pool into a quiet pool (Experiment 1) and reduce their preysearchperformance, measured as prey-search time in the noisy pool (Experiment 2). Furthermore, wetested the influence of the temporal structure and amplitude of the sound on the avoidance response ofboth animals. Both individuals avoided the pool with elevated sound levels, but they did not show achange in search time for prey when trying to find a fish hidden in one of three cages. The combination oftemporal structure and SPL caused variable patterns. When the sound was intermittent, increased SPLcaused increased avoidance times. When the sound was continuous, avoidance was equal for all SPLsabove a threshold of 100 dB re 1 mPa. Hence, we found no evidence for an effect of sound exposure onsearch efficiency, but sounds of different temporal patterns did cause spatial avoidance with distinctdose-response patterns. Show less
Foraging is made up of three steps: first, to search and encounter a suitable foraging patch; next prey has to be found, and finally the prey has to be caught and eaten. Behavioral responses to... Show moreForaging is made up of three steps: first, to search and encounter a suitable foraging patch; next prey has to be found, and finally the prey has to be caught and eaten. Behavioral responses to anthropogenic noise may lead to a disruption of vital activities within this process, such as area avoidance, or reduced abilities to locate or catch prey. Gaining insight into these behavioral effects starts with a thorough understanding of within- and between-individual variation in the baseline behavior of experimental conditions. In this study, we analyzed control trials for two captive harbor porpoises that were tested for spatial behavior in a set-up for experimental sound exposure. Data from trials without any experimental sound exposure were used to investigate relationships between the response variable - time spent away from the preferred area - and two other behavioral metrics: swimming speed and surfacing rate. The results show that these metrics can be used as independent measures, the first being correlated to the response variable, the second uncorrelated. Combining the two makes a better and more complete judgment. Performing an adequate exploration of the variation in behavior during control trials is important, as it will aid scientists in revealing and interpreting effects of disturbance in sound exposure trials. Show less
Liew, T.S.; Kok, A.C.M.; Schilthuizen, M.; Urdy, S. 2014
