How Fish Find Your Bait: Sight, Smell, Hearing and the Lateral Line

Six senses, and the order they use them

Minnesota’s Department of Natural Resources teaches fish biology to school groups through its MinnAqua programme, and its lesson on the subject opens with a count most anglers get wrong. In addition to taste, smell, sight, hearing and touch, fish have a sixth sense — the lateral line, which senses vibration in the water. The programme calls it an extension of hearing.

More useful than the count is the sequence. The agency describes a fish approaching a lure like this: it hears and feels its way to the lure with its ears and lateral line; when it sees the lure, it judges whether it looks like something it usually eats; it might then smell or taste the lure before eating it.

Sight comes third. That ordering explains most of what follows.

The lateral line

The agency’s description of the structure is precise. A fish’s lateral line is a network of ultra-sensitive nerve endings running along its sides from the gills to the tail. It consists of tiny pores containing hairs connected to nerve endings beneath the skin, and the hairs detect the location and direction of vibrations in the water.

What it is for, in the agency’s words:

• finding a meal, by sensing smaller fish swimming nearby
• avoiding becoming one, by sensing lurking predators
• swimming in a school without bumping into the others

And what it means on a dock, from the programme’s take-along guide: fish have a vibration-sensing lateral line, and loud talking and loud footsteps can easily distract or frighten them away from your bait. Sound in air mostly reflects off water; a boot on a plank goes straight in.

Hearing

Fish have ears, even though you cannot see them. They do not need openings on the outside, the agency explains, because sound travels so well through water; the inner ear is built like a human’s, with receptors for balance and hearing.

The lesson’s illustration of the sensitivity: fish hearing is so acute that they can hear a worm wiggling at the bottom of a lake. Its warning follows: even the faintest sound can spook fish. Combined with the lateral line, this is the sense that reaches a fish first — before it has seen anything.

Smell

Fish use their noses for smelling rather than breathing. Through the nostrils — usually two openings on either side of the snout — a fish can smell food from great distances, the agency says; it swims to the source and uses its taste buds to decide if the thing is edible. Salmon navigate hundreds of miles back to their birth stream on smell and taste.

Fish also use smell to sense danger, and here the lesson gets specific in a way that matters at the tackle box. Many fish can smell people, and will swim away from any bait that smells like:

• hand lotion
• perfume or deodorant
• tobacco
• gasoline
• insect repellent

That list is a description of most anglers’ hands on a summer morning. The agency’s point is not to buy something to mask it; it is to rinse before you bait up.

Taste — including without the mouth

Fish have tongues with thousands of taste buds, like people. Two species take it further, and both matter to anglers.

Walleye have taste buds on their lips and faces, so, in the agency’s words, a walleye can taste a fishing lure without ever opening its mouth. The lesson offers this as the likely explanation for something walleye anglers describe — a “bump” without a bite — as a finicky fish tasting the lure. Wisconsin’s DNR’s advice to fish walleye slowly and give them time to take the bait fits the same picture.

Catfish have taste buds on their bodies from head to tail, and barbels. The Minnesota lesson describes barbels as soft, whisker-like sensory structures above and below the mouth that work like taste buds; Wisconsin’s DNR calls them fleshy sensors capable of feeling and tasting, eight of them. Catfish drag their barbels along the bottom to find food, and when they touch something edible — the Minnesota lesson’s examples are a dough ball, chicken liver or stink bait — the fish stops and takes a bite. Wisconsin’s DNR draws the conclusion: catfish depend more on smell and touch than on sight to find their dinner, which is why they feed at night and in turbid water without difficulty. Our catfish fishing and live bait guides list the baits that exploit it.

Sight

Sight is third in the sequence, but it decides whether the fish commits. The agency’s phrasing: when the fish sees the lure, it can tell if it looks like something it usually eats.

Two points from the lesson about the angler’s side of the glass. Light bends when it passes from air into water, which shapes what a fish can see above the surface; the lesson’s practical advice is to stay out of a fish’s field of vision by crouching or sitting at the water’s edge rather than standing over it.

Species differ here more than anywhere. Wisconsin’s DNR describes walleye eyes as highly sensitive to light — the reflective tapetum lucidum is what makes them glow in a torch beam — which keeps the fish deep by day and feeding at dusk and after dark. Our night fishing guide covers that, and lure colour covers what fish can and cannot distinguish underwater.

Touch, and why slime matters

Fish feel with their skin and, in the whiskered species, their barbels. The angler’s contact with that sense is at the landing net. MinnAqua’s handling guide explains that a fish produces slime on its skin as protection, and that dry hands or a rough net wipe it away — which is the reason for wet hands, rubber nets and minimal handling in our catch and release guide.

What to do with all this

The agency lesson ends by asking students to describe how anglers can reduce the chances that fish detect their presence, and the answers are the summary of this page:

None of it requires buying anything. It requires believing the fish can hear you, which the agency that teaches this has been telling children for years.