Networked hydrophone arrays for passive acoustic recording of underwater sound

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The underwater soundscape, while once thought to be quiet, is in fact a noisy environment filled with sounds coming from a variety of sources including the bustling activities of animals and the movements of the sea. This myriad of sounds can travel enormous distances in all directions due to the excellent transmission of sound in water. Fishes, as the predominant vertebrate species in the aquatic realm, are a prime contributor to the biotic sources, using acoustic emissions ("calls") for signalling in mating and territorial contexts. While there is a substantial body of literature describing the soundscape in marine waters and using call outputs to identify commercially-important spawning aggregations, there is much less known about freshwater acoustics and how these species interact acoustically. Apart from its importance in identifying spawning aggregations of important species, the necessity of understanding underwater acoustics in freshwater is vital due to increasing amounts of underwater noise sources. In the marine environment, ambient underwater sound has increased by 3 dB per decade since the 1970's, mainly from the increase of shipping activity. From commercial and recreational boating to increased interest in citing offshore wind farms in the Canadian Great Lakes ecosystem, anthropogenic noise sources are increasing in duration and intensity. While it is clear that loud bursts of sounds can disrupt fish behaviour and even damage inner ears, the effects of more sustained sound sources are less well understood. With the increase in anthropogenic sound in this basin and the important role of acoustics in many fish species, an enhanced understanding of the soundscape in the Great Lakes ecosystem is vital to protecting commercially and ecologically important fish species. We seek support for a networked hydrophone array to allow us to passively record underwater sound to conduct numerous research projects on acoustic communication and noise pollution in Canada's freshwater marine environment.