Ships and Midshipman Fish: Does boat noise influence aggression in a highly vocal fish?




Woods, Mackenzie

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Underwater noise from anthropogenic activities such as recreational boating and commercial shipping has drastically increased over recent decades and is still continuing to rise. An increasing amount of research has shown that anthropogenic noise has been negatively affecting marine animals in several ways. Fish have received relatively little attention in these studies despite being the most speciose marine vertebrates, the majority of which rely on sound reception. Many fishes can not only detect, but also produce sound and are therefore highly reliant on noise for communication, prey and predator detection, and navigation. One of these species is the plainfin midshipman, Porichthys notatus. These fish have an extended parental care period, during which the males guard their nest and eggs until their offspring have hatched. I am studying the effect of boat noise on the aggression of males during their nest defense; I hypothesized that males would be more aggressive in the presence of boat noise than in ambient conditions. I kept male midshipman fish in tanks with artificial nests and ran trials where they were exposed to a crab threat stimulus in the presence and absence of boat noise and then scored their aggressive behaviours from video footage. The fish exhibited a higher level of overall aggression in the noise treatments (likelihood ratio test: χ² = 3.70 p-value: 0.05). Unnecessary aggression is energetically costly and alteration of male behaviour during their breeding season - an ecologically critical period - could impact the reproductive success of this species. Furthermore, these results may strengthen our understanding of the impacts of underwater noise on other ecologically important fish species.



marine biology, plainfin midshipman, Porichthys notatus, noise pollution, bioacoustics, animal behaviour, ecology, territoriality, boat noise, anthropogenic noise, parental care, intertidal, reproductive success, fish