What do fish hear?

I recently had an awesome opportunity to go fishing with one of the world’s foremost experts on how fish hear: Dr. Arthur Popper, from the University of Maryland. He’s spent an entire career focusing solely on how fish hear things, and how they react to sounds. Wait a sec – fish don’t have ears, do they?! Actually, they do have inner ears. We can’t see them because they’re inside the fish’s head. As Popper explained, since sound waves travel through liquids and solids rather well and a fish is water-based itself, they don’t need to have outer ears with holes exposed to the air, as we do. The sound waves travel right through the water, through the fish itself, and to its internal ears.

Wait just another sec – we always read about the fish’s lateral line, which it uses to sense vibrations in the water. Doesn’t that preempt “hearing”? Not really. In reality, fish use both organs to sense what’s going on around them. Think of it this way: when a plane roars overhead, you both hear it with your ears and feel it via vibrations travelling through your body, right? Though the mechanics may be different, with a fish it’s essentially the same thing. So, how can we anglers apply this knowledge? Dr. Popper mentioned a few key points as we fished, which were fascination.

First off, fish hear only at very low frequencies. So much of what we think they hear and what we can hear, they don’t. However, remember that they may still sense the vibrations via their lateral line. Secondly, sounds don’t travel well from air to water, but they can be broadcast through a solid – like your boat. So it stands to reason that sound-deadening properties in a boat (cored hulls, foam decking, foam insulation, etc) could be beneficial in preventing sound transmission from you and what you do aboard, to the watery world below. Third and probably most important to anglers, like any animal fish will become acclimated to sounds. In a backwater area where boats are few and far between, a running motor could grab their attention and potentially spook them. But in a high-traffic area where boats go roaring by all the time, the fish are used to the racket and one boat more or less is probably irrelevant.