Context-dependent effects of anthropogenic noise on nest defence in a singing toadfish

Noise pollution has been steadily increasing in the ocean, negatively affecting aquatic ecosystems by causing both behavioural and physiological deficits for many marine animals, including fishes. To date, most research investigating the effects of noise on fishes has been conducted in controlled laboratory settings; however, these experimental conditions often lack ecological validity, and it is largely unknown whether the effects observed in aquaria are representative of real-world responses for animals experiencing noise in the wild. In this study, we used a combination of laboratory and field playback experiments to assess the effects of noise on nest defence and parental care behaviours in an intertidal-breeding toadfish, the plainfin midshipman, Porichthys notatus. Nest-guarding males without eggs in the laboratory exhibited a nearly four-fold increase in defensive behaviours under boat noise playbacks compared to under ambient conditions. However, in the field, no significant changes were detected in the defensive or parental behaviours by guarding males with eggs under exposure to noise. Our study demonstrates that anthropogenic noise can impact nest defence behaviour in plainfin midshipman males, but also that its impact depends on contextual cues such as testing environment, presence of eggs and the noise stimulus used. Our results highlight the urgent need for more field studies and for studies that pair and compare laboratory versus field results to quantify and mitigate the potential harm caused by noise pollution to organisms and populations in coastal environments.