Do man-made sounds affect fish?

Written By:  shelteredcove December 28, 2017 at 6:15 am

How about this story: a school of bluefin tuna force their baitfish to the surface and then attack from every angle. The fisherman motors closer to get a better look, and the tuna dove back underwater. He pulls the outboard motor out of gear, and seconds later, the tuna school is back on the attack. Shift again, and again the tuna retreat. Back to neutral and the tuna returned.

Does this sound familiar to you, or has it happened to you? Most fisherman and scientists agree that fish can hear, but which sounds can they hear, and which repulse or attract them, and which do they ignore? How well do they hear, and can you put this information to work for you to attract fish?

Sport Fishing Magazine (https://www.sportfishingmag.com/noise-factor-fishing-skills) ran a great article about exactly this: the effects noise has on fish. In the article, they explain that fish sense sound underwater via two sensory organs: bony structures called otoliths in the inner ears, and an organ called the lateral line. For the most part, fish use the inner ears to sense sounds at a distance, and the lateral line for sounds less than a body’s length away.

Fish use their hearing for survival, mating, socializing, and protection. How well they hear or use their ability, varies based on the species of fish. The article states that fish that stay in relatively deeper waters (like bluefin tuna) don’t depend on their hearing as much as fish that are in more shallow waters (like white seabass). The white seabass uses this hearing sensitivity to locate one another and form schools, but the same senses allow this species to hear a range of sounds, including man-made noises on the boat itself, such as slamming a deck hatch or rattling an anchor chain.

While the waters carry sound 5 times as fast as the air, there are plenty of other noises being made underwater that are capturing the attention of the fish that you are looking for. However, you still should practice being stealth when maneuvering near a hot spot. This concept is proven by tapping on an aquarium, the fish scatter. The vibrations of the sound waves underwater startle them.

While the old fisherman’s superstition seems to be true that fish sense sound, it’s not as bad as it is made out to be. Newly introduced sounds bother fish, so the more silent you become, the more you will be successful, but if you have to make noises, make them consistent. Constant noise becomes part of the environment and less distracting to the fish. This even applies to people talking: divers can hear a conversation above water, so it is safe to assume that fish can too.

In reality, this is not a new thought. Fisherman for years have always held firm that noises can affect fishing, but we now know that different types of fish are affected differently from various man-made noise. In shallow water, it is best to turn off trolling motors and use a push-pole so as to not disturb the fish below.