From the desk of Bob Boese

BLUEGILL EYESIGHT - ONCE AGAIN (Can they see your fly?)

Bob Boese - Apr 22, 2013

The best tied fly in the world can't catch fish that don't know it's there.

Once again we'll discuss bluegill vision. We've been there and you might also want to look at: WHAT BASS SEE (Part I) and

Gautreaux's grandmother has failing eyesight and went into the appliance store where she looked around for a television until she found just the model she wanted. She called over a sales clerk and said: "I want to buy that television."

"You don't want that," the clerk answered. "That's a...."

"Don't tell me what I don't want," she snapped, "I want that television!"

"But you don't understand, You don't want that."

"And why not!?"

"Because that's a microwave."

Bluegills (and their sunfish cousins) have a physiologically limited eyesight. Even so, and science aside, there are obvious indicators that will help you catch vision-restricted bluegills.

To better understand bluegill, put hour hands in a prayerful position (palms together) and put them on your nose touching your forehead. Without binocular vision, your depth perception is mostly gone. Your focal length for clear vision may be severely affected and your eyes must refocus when something passes in front of your face. Even so, your new limited range of binocular vision is still better than a bluegill. Bluegills are nearsighted. Even in good conditions, the fine details of prey may not be apparent to a bluegill until it is six inches away. For this reason, they rely primarily on their other senses, particularly their lateral line, to alert them of prey. [See articles cited above.]   

If you have no other clues where to catch fish, your first observation should be the color and clarity of the water. What science tells us is that a bluegill's eyes are somewhat like a camera. Light enters through a clear lens and focuses on the retina. The lens is spherical with a high refractive index (the measure of the bending of a ray of light when passing from one medium into another) to aid in focusing. Like a zoom lens, bluegill focus by moving the lens in and out, but, unlike humans they cannot dilate or contract their pupils because the lens bulges through the iris and the iris is fixed. You can watch a cat's pupil's change from pinpoints to dime size depending on the amount of light. Bluegill can't do that. The iris allows light to enter the eye through the fixed center aperture only, while blocking out light coming in from beyond the edges of the fish's field of vision. Receptor cells in the retina make adjustments to any changes that may occur in the brightness of the light. Every retina has rod cells and cone cells. Cone cells are color receptors used when the light is brighter. Rod cells show black, white and intermediate grey shades, and are sensitive for darker situations. Rods or cones or both, compared to humans, bluegill have a severely restricted eyesight, that is not helped by their environment.

Silt and other suspended solids, or turbidity, can significantly reduce underwater visibility because particles in the water scatter the light. Wind and waves (even little ones) can muck up the downwind side of a water body. Floating vegetation can blanket even clear water and surface turbulence will make it worse.

Movement or vibration (which can be detected at distance) is the first signal to a bluegill that food might be nearby, and it may only have a moment to attack once the fly is close enough to see if it is actually food. It is often more productive to use a fly that causes some motion of the water. A bluegill knows what its home waters sound (or feel) like. Motion doesn't have to be spinner blade rough, but rubber or silicone legs, stiff or long hackle lends vibration attractiveness. The motion will help alert the bluegill that potential prey is around. Even when the fly is a foot or so away, a bluegill may not be sure it is actually prey. Bluegill will often "taste" a fly before taking it, to confirm that it is not a random piece of vegetation. Consequently, a fly with a bit of vegetation on it will almost never be attractive to bluegill. Check your fly often to remove debris.

Bass are infamous for attacking noisy flies because, among other reasons, the disturbance irritates them. Sometimes bluegills do the same, but much less often. When a dry fly lands on the surface and a bluegill attacks it immediately, that is almost certainly an involuntary reaction to potential food suddenly landing in its field of vision. Chances are the bluegill never got a really good look at the fly, and chances are equally good that a fly landing in the same place might not have drawn the attack if the bluegill were slightly turned in another direction. If you liked where you cast, there is no sin in casting there again. Bluegill are sensitive to anything that might suggest the presence of a predator, but are not particularly line shy or even hook shy. A bluegill that has been caught and released still has difficulty in overcoming the instinct to eat a tasty looking fly. If your likely looking spot doesn't produce a strike, subsequent casts often prove that it was an eyesight issue.

Bluegill have a very limited basic understanding of things outside of their wet world, and if they have ever seen insects land on the water, there is a likelihood that they might not associate a landing fly with food. A lot of factors have to be at work for top water attacks to occur. The fly must resemble food. Resemble means general shape, not necessarily identical. The water must be nearly calm. Rain or wind disturbs the surface and causes refraction of light thus difficulty for the bluegill to distinguish anything on the surface. Also, the landing must be realistic. Since a bluegill's diet is mostly small insects, a big splashy landing is not the best choice. If a fish is near the surface, its field of vision may have a diameter of a foot or less and bass attacking prey are splashy. The deeper the fish is, the larger diameter it can see on the surface, but the more restricted its clear vision.

Bass are reactive, bluegill are contemplative. Unless it is a large insect, the creature will not create a "splat" and, unless the bluegills are being very aggressive, neither should your fly. As opposed to a noisy fly that irritates a bass into striking, surface flies for bluegill, even poppers, should only disturb the water enough to affect the bluegill's lateral line receptors. Round or torpedo shaped dry flies were the favorites for generations, for a reason. If there is a large pop, bluegill will often retreat from the fly, which must then be left to lie still until the rings in the water dissipate.

In contrast, when a wet fly or nymph passes across the vision field of a bluegill, there are two other factors at work: distance and time. A bluegill's diet of insects generally inhabits the bottom of a pond. For these reasons, the key to bluegill wet/nymph fishing is low and slow. Hundreds, maybe thousands, of wet patterns will catch bluegill. The fly need not be a replica, but should be reasonably insect-ish. Why? Because wet insects tend to resemble nothing more than a glump of body parts and a bluegill's vision is frequently not adequate to distinguish a generic insect shape from the real thing.

But, generic doesn't mean any shape, it means something that vaguely resembles whatever insect is predominant in the water. This can depend on many factors, primarily size and color.

Don't think a size 8 streamer hook 3x long fly is going to fool fish feeding on size 14 bugs. Similarly, consideration of color show that warm colors disappear first with depth and turbidity. Reds and oranges may appear dark, while fluorescents and cooler colors retain their color in less light (i.e. greater depth). Of course, if the water has no florescent chartreuse or bright blue insects, such visibility is wasted. In the shallows, colors retain their true shade, except, and the farther it is from the fish the less true the color will be. Shades of green and brown/tan are often very effective because they resemble insects but stay true to color. Similarly, colors combinations that contrast may be easily seen, but not attractive to the fish. The wildfire tiger color combination, yellow-orange-red-green, is attractive to bass because it resembles a bluegill. It is not as attractive to bluegill because they won't waste the energy to chase down a fish when other food is available.

A final suggestion comes from the Odd Couple where Felix explains that you should never assume because it makes an ASS of U and ME. Going back to your likely looking spot, you have chosen that based on good reasoning, and assuming otherwise is unlikely to produce fish. Never assume bluegill see your fly and never assume a single fly is the only way to go. A popper dropper or double wet/nymph is double the chances for being seen and allow more flexibility in shapes and colors.

Widow Marie Soileau was the church gossip, and self-appointed monitor of the congregation's morals. She was always looking for sinners and kept sticking her nose into other people's business. Members she threatened to name as sinners feared her enough to maintain their silence. Every day she watched all of the town's hotspots and eventually accused T-George of being an alcoholic after she saw his pickup parked in front of the Mayeaux's bar all afternoon. She told anyone that would listen that they should assume exactly what he was doing there.

T-George heard about her gossip. Later that evening, he parked his pickup in front of Marie's house, walked home, and left it there all night.

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