Motorboat noise playback during development limits reef fish growth and impairs predator responses with carryover...

Motorboat noise has been found to affect the physiology, behaviour and even survival of embryos, juveniles and adults; however, whether effects persist beyond a brief period of noise exposure or are cumulative throughout life is currently unknown. We evaluated the long-term effects of motorboat noise playback on the escape response and growth of a common reef damselfish, Acanthochromis polyacanthus. In a tank-based experiment, using a split-brood design, fish were exposed to playback of motorboat noise or reef sound prior to hatching (parents and embryos) and/or as juveniles for up to 78 days, and were subsequently tested for their escape response in the absence of noise and measured for growth. We found that individuals exposed to motorboat noise prior to hatching and as juveniles were less likely to respond to a simulated predator attack than those that had experienced only reef sound, and when they did respond they were more likely to swim towards the predator. We also found that individuals exposed to motorboat noise as juveniles were smaller compared to those exposed to reef sound, regardless of whether they were exposed to motorboat noise or reef sound prior to hatching. Our results demonstrate that exposure to motorboat noise during early development has the potential to affect growth and disrupt the escape response of juveniles, even when the escape response occurs in relatively quiet conditions. Limiting motorboat traffic close to reefs during the breeding season may mitigate the adverse effects of motorboat noise on reef fishes during the vulnerable early life-stages.