Multiple exposure to thunderstorm sound in Nile tilapia (Oreochromis niloticus): physiological response and stress recovery

The present study investigated the impacts of multiple thunderstorm-sound exposures on growth and respiratory parameters in Nile tilapia (Oreochromis niloticus) in order to evaluate the acoustic stress response. Thunderstorm-sound exposure for 3 hours triggered respiration speed with an alarm reflex and rapid elevation of opercula beat rate (OBR) and pectoral wing rate (PWR), which increased two-fold over the control with no sound treatment, and peaked (OBR, 71.33±5.86 beat/min; PWR, 75.00±3.61 beat/min) in 10 hours after initiation of sound. Thereafter, respiration rates declined over the following days and returned to near-initial levels (45.33±4.04 beat/min OBR and 43.00±1.00 beat/min PWR) by day 3, an indication that fish recovered from thunderstorm-sound stress after 3 days of exposure. However, the same reaction course was observed each time of multiple sound exposures, repeated 20 times in a row with 4-day intervals, underlining that fish could not attune to repeated thunderstorm sound. Reduced voluntary feed intake as a result of anxiety and appetite loss was recorded in fish exposed to multiple thunderstorm sound, resulting in 50% less growth compared to those without sound treatment by the end of the 80-day experimentation. Therefore, it is advisable to monitor fish behavior during the 3-day stress period after a thunderstorm event in order to prevent waste from excess feeding, that in turn may contribute environment-friendly aquaculture for the future and sustainability of the oceans.