Whether fishing for trout from the banks of a small stream or wading in a shallow river, every angler knows how skittish these fish can be. They have excellent vision, and if you can see them they can probably see you. But keen vision is just one of their sensory defenses. Trout also hear extremely well, and they have one sensory system that humans can only imagine.
Trout ears are simpler than those of terrestrial vertebrates. They have only an inner ear. Land-based vertebrates also have outer and middle ears, concessions to the relatively slow speed of sound waves through air. In water, sounds travel faster and farther so an inner ear suffices.
A trout's inner ear consists of a series of canals and chambers that transmit sounds to sensory hairs that send signals to the brain. These signals enable trout to both hear and maintain balance.
Because sound travels so well in water even the sound of a lure landing on the surface can alert a trout to danger. Anglers wading on slippery rocks should realize that every slip, every stumble, and of course, every fall warns nearby trout of potential danger. So move slowly, smoothly and quietly. Fortunately, noisy rapids help obscure your presence.
Though keen vision and excellent hearing might seem sufficient to keep trout aware of their immediate environment, they, and other fish, have a third sensory system that works even in muddy, dark and noisy water. The lateral line system is a series of pores that runs along the sides of the body. They house structures --again sensory hairs -- that can detect changes in wave patterns and water pressure. It helps smaller fish detect the approach of bigger fish. And its what enables a school of fish to move as a super-organism. They move seemingly in unison because they can sense each other's presence. So again a wading angler is at a disadvantage.
If you're eagerly anticipating opening day of trout season, keep their sensory abilities in mind. Usually they can see you, hear you and even feel your presence.
Biologist, author, and broadcaster Scott Shalaway can be heard 8-10 a.m. Saturdays on 1370 WVLY-AM (Wheeling) and online at www.wvly.net. He can be reached at www.drshalaway.com, email@example.com and 2222 Fish Ridge Road, Cameron, WV 26033.