Arctic Conservation planning

Boat noise reduces vocalization rate and alters vocal characteristics in wild plainfin midshipman fish

Woods, M., Halliday, W., Balshine, S. & Juanes, F.

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This study looked at how motorboat noise affects the sounds made by wild midshipman fish.

Key points

• Male fish decreased their aggressive vocalizations by four times when exposed to boat noise.
• The noise also caused the fish's mating hums to get higher in pitch, and their aggressive calls became louder, showing that the fish adjust their sounds in response to the noise (a behavior known as the Lombard effect)
• This is the first time the Lombard effect has been observed in fish exposed to real boat noise.
• This could have negative consequences for their survival and reproduction, as vocalizations are important for defending their nests and deterring predators.
• The findings stress the need for noise reduction strategies, like quieter boats or slowing down vessels, to protect marine life from the impacts of human-caused noise.

Abstract

Anthropogenic noise pollution has been accelerating at an alarming rate, greatly altering aquatic soundscapes. Animals use various mechanisms to avoid acoustic masking in noisy environments, including altering calling rates or the frequency (pitch) of their vocalizations or increasing the amplitude (loudness) of their vocalizations (i.e., exhibiting the Lombard effect), but few studies have examined this vocal plasticity in fishes. We tested the effects of in situ motorboat noise on the agonistic and mating vocalizations of nesting plainfin midshipman fish (Porichthys notatus), and found that midshipman fish reduce and alter their vocalizations in the presence of boat noise. During boat noise, fish produced four times fewer agonistic vocalizations compared to ambient control periods. The fish also increased the frequency of mating hums and the amplitude of grunts and growls during boat noise. This study is the first to experimentally demonstrate the Lombard effect in fishes using real motorboat noise.

Recommended citation

Woods, M., Halliday, W., Balshine, S. & Juanes, F. (2025). Boat noise reduces vocalization rate and alters vocal characteristics in wild plainfin midshipman fish. Marine Pollution Bulletin. https://doi.org/10.1016/j.marpolbul.2025.117563