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Fish Stories: Fish Eyes

How to Think and See Like a Fish

October 19, 2006
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The hungry beast spotted the squid limping along the surface.

The squid, which was following something big, dark, and rumbly, was sick or injured. It wasn’t swimming as squids usually do, yet it managed to keep perfect pace with the rumbler. A few fast, hard pumps brought the beast closer. Now it could see that there were other creatures behind the rumbler. Several looked like fish, some it couldn’t identify, and all were swimming as though they, too, were injured – a smorgasbord of easy meals. It charged, swimming furiously until it was inches from the squid, then it whipped its head through the ocean’s surface. Cool air hit its skin as it opened his jaws wide…and shouted, “Hey, Len, toss me a Coke, will ya?”

No problem. The least I could do for The Beast, otherwise known as Don Maher, Boating’s scuba expert. He had, after all, volunteered to jump overboard more than 50 miles offshore into 800 feet of water to help answer a question that has run through the minds of countless anglers: What do fish see when they look at what you’re trolling?

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Good question, and if you ask it, all you’re going to get is guesses and speculation. Why? Well, for starters, we’re not fish – and the fish we know aren’t talking. So it was time to look for answers.

Yes, we could have done this in a pool. But you have to be in the ocean, and risk becoming bait yourself, to get the full effect of the depth, color, and rolling waves.

Here’s you’re Coke, Don. Now get down there and be a fish.

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The Eyes Have It

Naturally, we realize that people and fish don’t see things in the same way. So we found a fish vision expert, British marine biologist Daniel Bagur, who has done extensive research on big game fish.

The first thing Bagur tells me is that in some ways the eyes of a fish aren’t all that different from our own. Both species use the same basic process: Light impulses are modified and focused in the lens, then gathered by cells in the retina. These are attached to the brain via the optic nerve. Our retinas, like theirs, have receptors called cones and rods. Cones are color sensitive and used in open daylight. In some fish, including billfish, cones are present only in the upper half of the eye. Rods are more sensitive and used for low-light and night vision, but they’re limited to producing mostly black-and-white images.

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There are, however, two major differences between fish and human eyes. To start, big fish have big eyes, whereas ours come in one size. Take a look at the horse-size eyes of a 100-pound tuna. The larger an eye, the more cones and rods it has, and the more light it can gather. The second, and more important difference, is eye placement. Fish have one eye on either side of their head. This provides them with a huge field of vision, nearly 360 degrees. The downside: There’s only a small area in front of a fish where the field of vision of each eye overlaps. This limits its binocular vision, which is necessary for good depth perception, and limits a predator’s ability to judge distance to its prey until it is pointed directly at it. So it all boils down to this: We can see color and judge distance better; they can see more of what’s around them and in lower light levels. “When looking up from the depths, a fish would be limited to monocular vision,” says Bagur. “It would have a poorer sense of the exact distance between the bait and themselves than a diver would. Otherwise, a human wearing a diver’s mask would see a similar image as the fish.” That’s good news for our experiment. With his mask in place, Don submerges and the trolling begins.

Diver Down

First, we wanted to discover what a fish saw when a boat trolled by at a distance. So we found a lobster pot with a float to serve as a down line, and shoved Don over the side. He submerged to 40 feet and waited as we set out a diverse and dehooked spread that included a pink squid daisy chain, a rigged ballyhoo, a purple and silver squid-like MP Lures chugger, and a green Boone bird rig. I drove well into the distance, turned, deployed the lines, and trolled back and forth right next to the float. After a dozen passes, Don’s head popped up.

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“When are you going to start?” he asked. Looking up the entire time, from 40 feet down, he never saw a single lure. In fact, he never even saw the boat. “I could hear the prop’s whining noise,” he told us, “and I could see the surface. But no boat.” What gives?

“Distance and the turbulence would hide the bottom of the boat from view,” explains Bagur. “Even when the water is at its clearest, an object more than 100 feet away from a fish is not likely to be seen.” Add that to Don’s inability to see 360 degrees, as the fish can, and it’s likely that any fish down at his depth wouldn’t see the lures.

For the next 12 runs, Don moved up to 20 feet. At this depth, the view changed radically. He saw the boat moving overhead, spotted the rigged ballyhoo as well as the flapping bird rig. The purple squid and pink daisy chain remained invisible. Don reported that the bird rig was the easiest to see but that it didn’t look like anything in particular so much as a noticeable commotion. Ready for the real stunner? On each pass before he saw any lure or bait, he always spotted the “V” created where the line met the water. That means fish can see it, too.

At a depth of 10 feet, Don could spot all the lures. He reported that the ballyhoo was by far the most real-looking item in the smorgasbord. Like the bird rig, the daisy chain appeared more as a mass disturbance than a series of specific baits, and the squid was also tough to distinguish.

Join the Spread

For the next experiment, we trolled Don along on a line with the baits. This way, he would have a close-up view of the lures as they worked through the water.

First, the ballyhoo. With the ‘hoo’s tail twitching a couple of feet from his mask, Don reported that it looked so good, he was tempted to take a bite. Just one bummer-from about a foot away, the 50-pound test fluorocarbon leader was visible. When he shifted over to the daisy chain, he easily noticed the 150-pound test monofilament between each pink squid. The purple MP Lure was a real surprise: Even though it was invisible from a distance, it looked like a real squid up close. When the boat rocked or speed varied the tiniest bit, the skirt flared out, and to Don’s eyes, it looked like the real deal. The bird and daisy chain created so many bubbles that it was tough to focus on them – but maybe that’s a part of what fools fish into thinking it’s real food. I then put the boat into some fairly tight turns – into, with, and across the seas. I didn’t expect anything different to happen, but I was wrong. When Don told me what he saw, it was fascinating. “As the lures passed in and out of the prop wash and with bubble trails coming off of each corner of the boat, the lures remained visible. But the leaders – all 50- and 80-pound test fluorocarbon – disappeared in the disturbed water.” Aha -the advice of an old charter captain friend of mine suddenly made a whole lot of sense. He suggests making a small S-turn every two minutes or so, so that the lures and baits passed into and then back out of the prop wash. He claimed that 70 percent of his hits came during these turns.

Don’s observations may not stop the arguments that are bound to arise when two captains discuss what a fish sees, but we certainly learned a lot. Now, the next time a fish rejects your baits, you might be better able to understand what’s wrong by looking at it from a fish’s point of view. A

Fish Eye For the Angler Guy

•Use flat line clips, long leaders, or suspension from close rigger lines to make sure your lines don’t enter the water and make that highly visible “V” anywhere near the lures.

•Try pulling rigged ‘hoo a little more often. Time and time again, Don claimed it was the best thing we had in the water.

•Replace the heavy leaders in your daisy chains for lighter stuff that’s not so noticeable. All of the leaders were visible up close, even 50-pound fluorocarbon, so stick with the lightest possible.

•Zigzag as you troll, enough so that your lures pass through the whitewater and bubble trails.

•Consider a fish’s inability to shield its eyes from the sun. When the light is bright, try running a few subsurface lines.

•Don’t forget that fish have more rods than cones in their eyes. When it comes to lures or skirts, worry less about color and more about contrast; imagine what they’d look like in black and white.

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