Soundscapes in aquaculture systems

Abstract

Sound in aquaculture production systems remains poorly understood in terms of both biological effects and engineering possibilities. Open systems such as net pens and traditional ponds are increasingly being complemented by recirculating aquaculture systems (RAS). Each of these systems create soundscapes, which may have a significant effect on the high-value commercial species being farmed. The current study compared recordings of soundscapes from commercial net pens, earthen ponds, and concrete and high-density polyethylene RAS holding systems. Calibrated measurements of each acoustic habitat revealed the range and intensity of sound in each system type. Spectra of each type of holding system were overlaid with the hearing ranges and sensitivity levels of 4 commonly aquacultured fish, common carp Cyprinus carpio, European perch Perca fluviatilis, red sea bream Pagrus major and Atlantic salmon Salmo salar, and 1 crustacean, common prawn Palaemon serratus. The majority of ambient noise recorded in RAS systems and net pens fell within the 100 to 500 Hz range at or near fish hearing thresholds. While RAS systems are a markedly louder environment for species otherwise held in earthen ponds, the net pen environment clearly represents the most variable and loudest aquaculture holding system, reaching noise levels capable of eliciting a measurable physiological response in many species and revealing a likely source of chronic stress. The long-term stress response of culture animals and performance cost of inappropriate soundscapes remains undetermined. A precautionary approach and optimised system engineering is recommended to reduce the sound impact on culture animals to optimise growth performance.