ANTHROPOGENIC UNDERWATER SOUND AND ITS EFFECTS ON FISHES: A REVIEW OF SOURCES, SENSORY MECHANISMS, BIOLOGICAL RESPONSES, ECOLOGICAL CONSEQUENCES, AND RESEARCH PRIORITIES

Anthropogenic sound has become an increasingly important environmental stressor in marine, estuarine, and freshwater ecosystems. Fishes rely on acoustic information for communication, orientation, habitat selection, predator and prey detection, social interactions, and reproduction. Consequently, anthropogenic sound may interfere with biologically important sensory processes and produce behavioural, physiological, auditory, developmental, reproductive, and ecological effects. This review synthesizes literature on the major sources of anthropogenic sound affecting fishes and evaluates the mechanisms through which sound exposure produces biological responses. Evidence indicates that the effects of sound are strongly influenced by its frequency, intensity, duration, temporal pattern, repetition rate, propagation characteristics, and the distance between the source and receiver. Fish responses are also species-specific and depend on auditory sensitivity, anatomical adaptations, life stage, behavioural state, habitat, and environmental context. Documented effects include behavioural avoidance, altered swimming and feeding, acoustic masking, temporary hearing threshold shifts, stress responses, changes in energy allocation, reproductive disruption, and effects on early-life development. Impulsive sources, including pile driving and seismic airguns, may pose acute risks under certain exposure conditions, whereas continuous vessel and shipping noise can create chronic masking and disturbance over large spatial areas. However, important uncertainties remain because relatively few fish species have been investigated, particle motion is often inadequately measured, laboratory exposure conditions may differ from natural sound fields, and direct evidence linking individual responses to population-level consequences remains limited. The review concludes that anthropogenic sound should be regarded as a biologically relevant form of aquatic pollution. Future research should prioritize species-specific exposure assessment, long-term field studies, measurement of both sound pressure and particle motion, investigation of cumulative stressors, and greater representation of tropical, estuarine, freshwater, and developing-world ecosystems.