The effects of anthropogenic noise on the behaviour and vocalizations of plainfin midshipman fish, Porichthys notatus
Date
2024-01-11
Authors
Woods, Mackenzie
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Abstract
Noise pollution in the ocean has been accelerating at an alarming rate, drastically altering underwater soundscapes and negatively affecting marine life in myriad ways. Many marine animals, including fishes, rely heavily on sound for communication, navigation, and environmental perception, all of which can be negatively affected by anthropogenic noise pollution from activities such as recreational boating, commercial shipping, marine construction, and seismic exploration. While the effects of noise on marine mammals are well documented, far fewer studies have investigated the effects of noise on fishes, and even fewer have been conducted in the field using realistic noise stimuli. In this thesis, I use a combination of field and laboratory studies to investigate how anthropogenic noise affects nesting plainfin midshipman fish (Porichthys notatus), which breed in the intertidal zone and rely on acoustic communication for mate attraction and defence. I demonstrate that plainfin midshipman sometimes alter nest defence behaviour in response to boat noise, but that testing context, such as whether they are tested in the laboratory or the field, the presence of eggs, and the noise stimulus used, can greatly affect experimental outcomes. I also found that males in the wild significantly reduced the number of agonistic vocalizations but increased the amplitude (loudness) of these calls when a motorboat was driven continuously near their nests. Males also increased the frequency (pitch) of their mating hums. Such vocal adjustments in response to noisy environments are referred to as the Lombard effect—a widespread phenomenon typically studied in mammals and birds but rarely tested in fishes. This study is amongst the first to report changes in vocalization frequency and amplitude in fishes, and it is the first to demonstrate this effect in wild fish using experimentally introduced noise from a real motorboat. The results in my thesis contribute to our growing understanding of how noise affects fishes and demonstrate the need for additional field studies using realistic noise stimuli and ecologically relevant contexts.
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Keywords
animal behaviour, noise pollution, boat noise, bioacoustics, vocalizations, toadfish, parental care, nest defence, acoustic communication, Lombard effect, plainfin midshipman, fish behaviour, Porichthys notatus, Anthropogenic noise