International Fund for Animal Welfare

arine seismic surveys produce some of the most intense manmade noises in the oceans and these surveys often operate over extensive areas for extended periods of time. The juxta-position of intense sound sources and acous-tically sensitive marine mammals must give rise to concerns about possible adverse im-pacts. Intense sounds can potentially have a number of effects on marine mammals. In this review, we divide possible effects into four categories: physical (including physiological) effects, perceptual effects, behavioral effects, and indirect effects. Possible physical and physiological effects include damage to body tissues, gross damage to ears, permanent threshold shift (PTS. i.e. permanent reduc-tion in auditory sensitivity), temporary thresh-old shift (TTS. i.e. reduction in auditory sen-sitivity with eventual recovery), and chronic stress effects that may lead to reduced viabil-ity. The most likely perceptual effects would be masking of biologically significant sounds (e.g. communication signals, echolocation, and sounds associated with orientation, find-ing prey or avoiding natural or manmade threats) while behavioral effects could include disruption of foraging, avoidance of particu-lar areas, altered dive and respiratory patterns, and disruption of mating systems. Indirect effects might include reduced prey availabil-ity resulting in reduced feeding rates. There are a number of existing reviews of this topic. The comprehensive book on ma