Juvenile damselfish are affected but desensitize to small motor boat noise

- Boat noise is an important source of marine pollution.
- Capacity of fish to desensitize to boat noise and adjust their behaviour is unknown.
- Real boats are used to assess how boat noise affects fish behaviour and resilience.
- Juveniles recovered under a regime of constant boat noise after 20 min.

Anthropogenic noise pollution is rapidly increasing in the marine environment. Anthropogenic noise can mask biotic sounds, disrupting the successful transmission between caller and receiver, and can cause physical, physiological and behavioural changes in some species. The effect of noise pollution produced by small motorboats is of particular interest in shallow, coastal habitats where vessel numbers are steadily increasing. The present field study examined the effect of small motorboat noise on the behaviour of the juvenile common damselfish, Pomacentrus amboinensis, and their potential to perform typical behaviours when presented with increased noise over a short time period. Behavioural observations in the field (before, 1, 10 and 20 min after the start of boat noise) found there was an immediate decrease in the boldness and relative distance moved by P. amboinensis in response to the noise produced by a boat with a 30 hp 2-stroke engine travelling 30-80 m away. However, fish appeared to return to pre-boat noise exposure behaviours within 20 min. The immediate change in behaviour may alter mortality rates in the short-term, but the potential for de-sensitization to boat noise may allow long-term persistence in noisy environments if they survive the initial disruption.