Acoustic effects of underwater drilling and piling noise on growth and physiological response of Nile tilapia (Oreochromis niloticus)

Human-generated noises are considered as underwater sound pollution with potential short- or long-term impacts on behavioural responses and physiological reaction of aquatic living organisms. Few investigations are available so far on long-term influences of impulsive and continuous sound sources on physiological response of fish. In the present study, opercula beat rates and pectoral wing rates were monitored as a physiological stress response of ventilation in Nile tilapia (Oreochromis niloticus) exposed to long-term repeated and continued sounds generated from underwater construction work. Fish responded to underwater sound treatment with significantly increased opercula beat-and pectoral wing movements. Maximum ventilation rate was observed as a startle response of fish at initial exposure to underwater sound. The ventilation rates remained at high levels over the first 4 weeks and showed a declining trend thereafter. Fish growth was almost stable for the first 4 weeks, but shifted forward from day 45 onwards. We found strong evidence that fish could attune to repeated playbacks of underwater noise exposures since we found higher specific growth rates for the sound exposed fish from day 45 onwards until day 120, a so-called 'catch-up growth endeavour'.