relationship between ambient noise and dominant frequency of vocalizations in two species of darters (Percidae: Etheostoma)

Acoustic communication is used by many freshwater fishes for both courtship and aggressive interactions. Fish that live in shallow streams with fast moving water are often exposed to high levels of ambient noise, which could have an effect on the characteristics of their vocalizations. This paper investigates the aggressive vocalizations produced by two closely related species of darters. We measured ambient noise in their respective microhabitats, and found that both species produce aggressive drum vocalizations with a dominant frequency that corresponds to areas of low ambient noise. Previous studies have found quiet windows in shallow streams that have correlated to the dominant frequency of sounds made by fish that inhabit the streams. This is the first study, however, to show how the dominant frequencies of vocalizations of two closely related species occur in areas of low ambient noise within their respective microhabitats. This study supports other studies which show that ambient noise along with other physical features of the environment can affect vocal characteristics and behaviors in freshwater fish.