SIXTH SENSE
To dial up more fish, try tuning in to their lateral line
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Most fish rely on their sense of sight to capture prey, but they can also detect vibration and movement via the lateral line running along their sides and across their faces. This organ is so sensitive that fish such as walleye and bass can feel the hydro-acoustic trail of a cisco, shiner or baitfish that has just fled.
Who hasn’t made a cast with a surface bait, for example, and been shocked when a fish smashed it the second it touched the water. And not only do fish use their lateral line to help capture prey, they also use it to communicate with each other, distinguish objects and avoid predators. But how exactly does this sixth sense work, and how can anglers use it to their advantage?
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IDENTIFICATION SYSTEM
“It’s the neatest thing to take a magnifying glass and look at the sides of a fish,” says my good friend Steve Quinn, a renowned U.S. fisheries biologist. “You’ll see the small pores that run to the caudal fin and around the face of the fish. These little pores are openings to a liquid-filled canal that runs below the lateral line. They have hair cells that detect changes in the movement of water, giving them information to evade predators and find prey.”
Quinn says fish have to be relatively close to an object to feel it, typically using their eyes to spot it first, then sliding in behind it so they can switch over to their close-range lateral line identification system. Hydrodynamic stimuli such as the tail flap of a fleeing yellow perch sends out a current that remains in the water for some time, alerting fish via their lateral line.
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“There nothing like it in the animal kingdom,” Quinn says. “It is a marvel of evolution how these creatures can feel these hidden currents. Fish are tuned in to any changes in the speed of the water around them.”
Quinn also points to evidence suggesting the lateral line is so sensitive that a predator fish can distinguish if a movement was made by a crayfish flapping its tail or a shiner wagging its fins. He refers to this as a species-specific “signature.”
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GOOD VIBRATIONS
So, how can we exploit this remarkable sixth sense and incorporate it into our daily fishing plans? On highly pressured waters, Quinn suggests being a contrarian, noting the reverberations from trendy lures can actually be detrimental to success if the fish associate them with an unpleasant experience, such as being caught and released. Instead, he says it’s better to present something different and slightly erratic.
“Fish always react to things that are a little offbeat,” Quinn says. “They really relate to a change in the cadence of your lure, like a crankbait deflecting off a rock, a spinnerbait hitting a stick or a rattlebait that changes direction and alerts the fish that something is going on that might be valuable to investigate.”
I am reminded of two other things listening to Quinn. The first is that most predators use their senses of sight and feel in almost harmonious, lock-step combination. The second is that certain lure vibrations must inherently feel good and mimic favourite foods. Think of the effectiveness of whirring inline spinners and thumping paddletail swimbaits. The fish never seem to get conditioned to avoid them, so they must be striking the perfect chord.
“They’re highly realistic,” Quinn says of such baits. “It gets back to those vortices that are left behind by prey fish. These soft-plastics on a jig head are coming very close to that range, so the fish are fooled. It’s remarkable.”
Gord Pyzer is Outdoor Canada’s longtime fishing editor.
BONUS TIP: THE SOUND OF SILENCE
While the sense of hearing is integrated in a fish’s central nervous system, its role is remarkably subdued. Humans can hear frequencies of approximately 20 to 20,000 cycles, or hertz, per second. Fish, on the other hand, can generally only hear low frequencies from roughly 10 to 600 cycles. Fisheries scientist Steve Quinn says most rattling lures emit high-frequency sounds that resonate well with anglers shaking them in the bait shop, but go completely undetected by fish. Why? They simply can’t hear them.