Listening to a gently babbling brook might be restful if you're on the bank, but spare a thought for the riverlife beneath the surface. Fish that live in the noisy water detect the water's movements with sensory organs distributed on the skin. But when fish are hunting, can they distinguish the tiny vibrations produced by prey from the constant roar of flowing water? Knowing that there are two different types of sensory receptors in the fish's lateral line flow detection system, Max Kanter and Sheryl Coombs at the Loyola University of Chicago predicted that Lake Michigan mottled sculpin would still orient in the direction of an artificial prey, even when the current was as high as 8 cm s-1. The team analysed mottled sculpins' responses when they increased the flow through a tank, and how the fish reacted when they generated vibrations to simulate prey. As the current increased the fish oriented in the upstream direction, but could they still respond to the weak vibrations of an artificial prey at their side? Amazingly they could! The fish were filtering out the low frequency noise of the rushing water, to pick out the tiny prey vibrations above the background din (p. 59).

Kanter, M. J. and Coombs, S. (
). Rheotaxis and prey detection in uniform currents by Lake Michigan mottled sculpin (Cottus bairdi).
J. Exp. Biol.