Behavioural and morphological changes in fish exposed to ecologically-relevant boat noises

There is increasing concern about the effect of underwater noise on fish due to rising levels of anthropogenic noise. We performed experiments on the black bullhead (Ameiurus melas), a species with known hearing specializations and located within the Laurentian Great Lakes where there is significant commercial and recreational boat traffic. We tested and compared physiology (baseline cortisol), behaviour (activity, sheltering) and morphology (cilary bundles of hair cells) of bullhead to boat noise. At 140 dB re 1 μPa (-54.84 dB re 1m s-2) we saw clear behavioural effects in terms of both activity and sheltering levels despite no obvious morphological or physiological stress. Following both short and long period acute exposure to higher — but environmentally relevant — noise levels, bullhead were less active and sheltered more and also exhibited a decrease in cilary bundles. These results suggest that there are sublethal effects of anthropogenic noise on fish behaviour and cilary bundles which may have dir...