New Study Suggests Motorboat Noise Disturbance Increases Fish Mortality by Predation
Anthropogenic (or ‘human-generated’) noise affects many aspects of both terrestrial and land animals behavior: Aspects such as communication, hearing and movement are all affected and increasingly so since the dawn of industrial revolution and the motorised vehicule.
Studies of aquatic animals have suggested human noise pollution has negative effects on communication and foraging behaviors, however there are few studies of the direct effects that noise pollution has on wildlife survival and population trends.
In a recent study an international research team has demonstrated that motorboat noise disturbance, both real and playback of a recorded sound, have profound physiological and behavioural affects on fish that increases their chances of predation two-fold. With more motorboat users being registered every year, motorised boat related noise pollution is an increasingly prevalent problem in marine eco-systems.
The team studied the predator-prey dynamics of young Ambon Damselfish (Pomacentrus amboinensis) and their natural predator the Dusky Dottyback (Pseudochromis fuscus) during exposure to motorboat noise compared to ambient environmental conditions. They found that both motorboat noise and direct disturbance by motorboat caused elevated metabolic rates (an increase of 20%), elevated stress and reduced the efficiency of anti-predator responses, which doubled mortality rate by predation. Indeed stressed individuals demonstrated less ability to identify a predator and had less efficient “rapid startle response”: As they state “We found that when motor-boats were passing P. amboinensis were six times less likely to startle to a simulated predator attack compared with fish tested in ambient conditions”, to add to this response times were observed as being 22% slower.
To consolidate the negative survival impact of motor-boar noises on the Damselfish, the influence of motor-boat noise on predator strike-success rate was also monitored: The predator was more successful in situations with the motorboat noise needing 74% fewer strikes to capture their first prey and 2.9 more Ambon damselfish were consumed in a same duration compared to ambient conditions. It appears that motorboat noise does not affect equally both predator and prey leaving the damselfish open to increased predation.
Through their study the team obtained significant evidence that motorboat noise can have a detrimental effect on anti-predator behavior, especially at key transitional stages for young fish. This leads to a threat to prey population survival, with elements such as increased stress being at fault. It is not sure if the observations are applicable to a wide range of fish species but the findings provide important backings to the negative effects of anthropogenic noise on marine wildlife survival.
Simpson. S.D, Radford. A. N, Nedelec. S. L, Ferrari. M. C. O, Chivers. D.P, McCormick. M. I and Meekan. M. G (2016) “Anthropogenic noice increases fish mortality by predation” Nature Communications (7): 1-7
Full article available online: http://www.nature.com/ncomms/2016/160205/ncomms10544/pdf/ncomms10544.pdf
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