Effects of acoustic complexity on growth performance, behavioral responses, and waterborne cortisol dynamics in Nile...

Aquaculture intensification demands strategies that enhance productivity without compromising animal welfare. Auditory enrichment has emerged as a novel environmental intervention; however, the role of acoustic complexity in modulating physiological stress, behavior, and growth remains insufficiently explored. This study evaluated the effects of distinct musical genres on welfare and production performance in Oreochromis niloticus.

A total of 75 juvenile O. niloticus were randomly assigned to five groups: Classical, Rock, Pop, Electronic (EDM), and Control (no music). Fish were exposed to 70 dB acoustic stimuli for 4 h daily over 30 days. Behavioral responses were assessed using ethograms and the Novel Tank Test, while stress was quantified non-invasively through waterborne cortisol analysis. Growth performance was evaluated using final weight, relative growth rate, specific growth rate, and survival. Statistical analysis was conducted using one-way analysis of variance with significance set at p < 0.05.

Acoustic treatments significantly influenced stress physiology, behavior, and growth. High-tempo genres (Rock and Electronic) induced chronic stress, reflected by elevated cortisol levels (up to 0.90 ng g^-1 h^-1), increased aggression and erratic swimming, reduced specific growth rate (1.2% day^-1), and lower survival (67%). In contrast, Classical and Pop music promoted welfare, with reduced anxiety-like behaviors and stabilized cortisol profiles. The Pop group exhibited the highest growth performance, achieving superior final weight (13.67 ± 1.15 g), relative growth rate (142 ± 23%), and 100% survival. Behavioral observations suggested a unique "attentive immobility" state in the Pop group, potentially minimizing energy expenditure and enhancing metabolic allocation toward growth.

Acoustic complexity is a critical and manageable environmental factor influencing welfare and productivity in O. niloticus. While high-intensity sound acts as a stressor, structured auditory stimuli, particularly Pop and Classical music, function as effective enrichment tools. These findings support the integration of optimized auditory protocols as a low-cost, non-invasive strategy for sustainable aquaculture intensification.