Recreational boating activity has the potential to generate noise pollution that may influence wild fish. Such noise may be particularly relevant to fish engaged in parental care (PC), where alterations in behaviour could influence individual fitness and productivity of fish populations. Here, the PC behaviour of the freshwater largemouth bass (Micropterus salmoides) was examined to determine whether disturbance from boat noise altered paternal behaviour. Changes in nest-tending and brood-guarding behaviour were measured following exposure to noise treatments of 1-min duration using underwater playbacks of recorded boat noises. One experiment compared the behaviour of bass tending eggs before, during, and after exposure to high-speed or idling combustion motors, or an electronic bow-mounted trolling motor. No significant differences in the time on nest, number of pectoral fin beats, and number of turns between the pre-treatment, treatment, and post-treatment periods for all three motor types were observed. A second experiment assessed the impacts of noise (high-speed combustion motor only) on the behaviour of nesting bass across the development stages of offspring (i.e. egg, egg-sac fry, and swim-up fry). During the egg-sac fry stage, nest-guarding males turned significantly less on the nest during the noise treatment compared with the long-term post-treatment period, indicating a stage-specific impact of boat noise on parental behaviour. The effect was transient, however, and limited to the period that the noise was present. Given that PC and recreational boating activity tend to co-occur in nearshore areas, prolonged or frequent repeated exposure of nesting fish to boat noise during the egg-sac fry stage could have adverse consequences for fitness and reproductive output. Efforts to restrict recreational boating activity in the vicinity of fish engaged in PC (e.g. through the use of set-backs) would be a risk-averse approach to mitigating the effects of noise pollution on fish.

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Keywords Behaviour, Fish, Largemouth bass, Noise, Recreational boating
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Journal Aquatic Conservation: Marine and Freshwater Ecosystems
Maxwell, R.J. (Ryan J.), Zolderdo, A.J. (Aaron J.), de Bruijn, R. (Robert), Brownscombe, J.W. (Jake W.), Staaterman, E. (Erica), Gallagher, A.J. (Austin J.), & Cooke, S.J. (2018). Does motor noise from recreational boats alter parental care behaviour of a nesting freshwater fish?. Aquatic Conservation: Marine and Freshwater Ecosystems. doi:10.1002/aqc.2915