Natural Ambient Sounds as Sources of Biologically Relevant Information and Noise for Fishes

In the field of fish bioacoustics, sounds other than conspecific communication sounds have generally been viewed as background noise interfering with the detection of communication signals. However, many fish species do not vocalize but still possess acute hearing, suggesting that fish hearing may have evolved, in part, to detect and extract information from the “ambient sounds” present in the environment. This chapter highlights some of the major sources of natural ambient sound and discusses how they function as sources of biologically relevant information. Some fishes can extract information about larval settlement sites, spawning events, food sources, and approaching predators from natural ambient sound. Instances where natural ambient sounds function as noise are also discussed. Ambient sound can mask hearing and some vocalizing fishes have been known to either produce louder vocalizations or change vocalization rates to cope with increases in ambient sound levels. Several species living in shallow water habitats vocalize at frequencies that coincide with a dip in acoustic energy in the local ambient sound spectrum. Data on the behavioral and physiological responses of fishes to natural ambient sounds remains scarce. Such information could be important for understanding how anthropogenic sounds affect the survival and reproduction of fishes.