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Hooking the gullible: Fish researchers analyze the science of a lure.

Just about everywhere you go in the National Fresh Water Fishing Hall of Fame and Museum in Hayward, Wis., you'll find lures. On the walls and in display cases, vast arrays of fishing lures dominate the exhibits. Many of the baits mimic a fish's natural prey, such as insects, small fish, and frogs. One lure appears to be a creature straight from the Star Wars cantina. Another looks like a Ping-Pong ball--size Pacman with froglike eyes and Andy Rooney's eyebrows. Another resembles a hockey puck with an airbrushed paint job that would look at home on a 1970s muscle car. Yet another lure has the size, shape, and maybe even the hydrodynamic characteristics of a shoehorn.

"I think you could put a hook on almost anything and catch fish," says Ted Dzialo, the hall of fame's executive director.

As it turns out, hunger is only one of the factors that drives a fish to lunge for a lure. Research into fish behavior has been revealing other cues that fish find hard to resist, clues that lure designers might use to blind a fish to the sharp truth about what really awaits it on the end of a monofilament line. As for understanding what goes on in anglers' minds when they're choosing lures.... Well, that's another story.

AMATEUR SPOONING The first U.S. patent for an artificial lure was issued in 1852 to Julio T. Buel. While taking a lunch break on his boat one day, Buel accidentally dropped his spoon overboard. As the shiny utensil fluttered toward the lake bottom, the Vermont angler saw a huge fish zoom from the depths and repeatedly strike at it. Buel went home, chopped up his silverware, added a few hooks, and spawned America's fishing lure industry--or so the fish tale goes.

Today, recreational fishing is big business. According to a 2001 survey conducted for the U.S. Fish and Wildlife Service, more than 28.4 million anglers whiled away their time on the nation's freshwater lakes that year. They also spent about $17 billion on equipment. About $490 million of that total went to purchase lures and other artificial baits, says Forbes Darby of the American Sport-fishing Association, a trade group based in Alexandria, Va.

With that kind of money floating around, some companies rely on science, rather than trial and error and anecdotal reports, in their quest to develop the most alluring of lures. Many of the industry researchers' investigations focus on fish behavior to guide the development of lures, says Keith A. Jones, a director of research at Pure Fishing in Spirit Lake, Iowa.

"We'd like to know what 'turns on' a fish" says Jones, who's worked at the company for 19 years. To answer that question, he and his fellow luremeisters develop prototype baits in a variety of sizes, shapes, materials, and color schemes ... and eventually, they go fishing.

Before looking for waterside live action, however, the researchers put each lure through an assortment of lab tests. First, they examine its motion in a trough of flowing water, a fluid-filled analogue of the wind tunnels that aeronautical engineers use to test aircraft components. Slow-motion video recordings taken from several angles reveal a lure's movements in three dimensions and show, for example, how much a lure wobbles and how fast it swishes back and forth.

Next come tank trials with live fish. Sometimes the artificial baits are towed past fish in a long, straight tank. In other tests, they're hauled around in oval circuits for a specified number of laps. The researchers then compile statistics on how well a lure gets a fish's attention, for example, or how often it triggers the creature to strike.

Finally, in the most enjoyable part of the research-and-development process, the baits are field-tested on lakes and streams. Often, several years separate when a lure is first dreamed up and when it becomes available for sale.

SIZE MATTERS No lure works equally well on all fish. Luckily, one of the species that fish behaviorists frequently study in university labs--Micropterus salmoides, the largemouth bass--is the favorite target of many freshwater anglers.

About 11 million U.S. anglers actively seek this feisty fish or its cousin, the smallmouth bass Micropterus dolomieui, says Darby. These two hardy bass species found in lakes and streams nationwide thrill sports fishers by striking lures hard and putting up a good fight.

"They'll eat darn near anything" says Michael P. Masser, a fisheries biologist at Texas A&M University in College Station. While hatchlings thrive on microscopic plankton, adult largemouths eat worms, crayfish, other fish, and even baby ducklings.

Bass often show a preference for prey of a certain size. Peter C. Wainwright and his colleagues at the University of California, Davis have studied the feeding behavior of largemouth bass in their laboratory by examining high-speed video of bass strikes at live prey and also by implanting electronic sensors in muscles of the bass' head and jaws. During those studies, the scientists noticed that bass preferred prey that were about half the diameter of their mouths or a little bigger.

Jones' experiments at Pure Fishing show a similar partiality, but he notes that when fish are hungry, they'll go after prey that's much larger than their mouths. In field trials, Jones has caught smallmouth bass that were barely larger than the prototype lure he was testing.

While their maximum prey size varies, bass don't seem to go for prey smaller than a certain size, says Masser. "Maybe they do think anything small is worthwhile," he notes,

Both size and distance enter into fish-behavior experiments conducted at Loyola University in Chicago. John G. New placed a 20-centimeter-long largemouth yearling alone in a tank with a 4-cm-long fathead minnow. Typically, the bass first turned toward a minnow when it was a little over 40 cm away. At that distance, the minnow would stretch across up to 5[degrees] of the bass' visual field, about 10 times the angle that the full moon occupies in a person's field of view. Although the bass probably can see objects that stretch across one-hundredth that angle, results of News experiments suggest that the predator doesn't pay attention to such small, distant, potential meals.

So, for lure making, bigger may be better.

Beyond a lure's size, certain characteristics of its motion can attract a fish's attention. For instance, many successful lures mimic prey that are erratic or hurt, says Texas A&M's Masser.

That sort of movement frequently seems irresistible to largemouths, agrees Wainwright. In his lab experiments at UC Davis, bass often ignored live prey that was swimming normally but immediately surged the length of the tank to pounce upon an injured fish.

Wainwright and his colleagues also observed that, to conserve effort, bass adjust the speed and strength of their strikes for different prey. Slow fish such as goldfish don't elicit strikes that are as fast and hard as those that more-elusive victims, such as shad, provoke. Also, bass strike harder at larger prey than they do at smaller ones. Stronger strikes are more likely to ensure that the prey doesn't escape, Wainwright speculates.

ACCOUNTING FOR TASTE

There's good evidence to support the efficacy of lures that use chemistry to catch fish. Sometimes anglers spray a fishy or wormy scent on a hard-plastic lure, or a soft lure incorporates such feeding stimulants into its material.

Once prey has been taken into a bass' mouth, the fish judges its taste and texture and decides either to chew and swallow its victim or to spit it out, says Paul J. Linser, a biologist at the University of Florida in St. Augustine. He and his colleagues are among the researchers who have studied largemouth bass behavior during this final stage of predation.

In some of their experiments, the scientists fed bass goldfish and artificial food balls made of gels of varying compositions. Video recordings of largemouths after they had taken up food but not yet swallowed suggested the fish were grinding their food back and forth at the rear of their mouth between tough plates that have short, rasp-like teeth--the so-called pharyngeal pads. This chewing action pulverizes relatively soft food such as invertebrates and strips the scales off piscine prey, says Linser.

The experiments suggest that bass rely heavily on their sense of taste at this stage of feeding. Microscopic analyses of a bass' pharyngeal pads show taste buds scattered among the teeth. In lab tests where the artificial food balls didn't contain any feeding stimulants such as pureed shrimp or minced fish, 8 bass spit out the ball within 3 seconds. When feeding stimulants were present, even when they made up as little as 1 percent of the food ball, bass held the balls in their mouth longer and swallowed them significantly more often.

Lure makers recognize that the longer a fish holds a lure in its mouth, the more likely it is that an angler can set the hook and reel in the catch.

SOMETHING'S FISHY Not all aspects of lure design stem from research into fish biology or feeding behavior. Take color, for instance. The photoreceptors in a fish's eye often are keenly tuned to the creature's environment, says Jones.

Many species that live primarily in clear water, such as those that inhabit coral reefs, have photoreceptors that are sensitive to red, green, blue, and even ultraviolet wavelengths of light. Fish that live in waters murky with sediment or stained with pigments from rotting vegetation, however, often have fewer types of photoreceptors. Largemonth bass, for example, have only receptors that detect primarily red and green wavelengths.

So, what explains the dizzying profusion of lures with blue and purple--colors that a bass can interpret only as varying shades of gray? Blame a phenomenon that Jones calls the "jewelry effect"

"We design lures for the fish, but fish don't buy lures" says Jones. "It's hard to convince anglers that a lure's color doesn't make much difference."

Jones says that when he started designing lures, he underestimated the need to make them aesthetically pleasing to anglers. Even today, some of his baits' designs need to be tweaked to increase sales.

For example, 2 years ago, one variant of a lure his company makes had a smooth, white body, a caramel-colored back, tigerlike stripes, and painted-on eyes. Slow sales quickly relegated that lure to bargain bins, even though it attracted fish. The company then remodeled the lure to include a textured, olive-toned surface with scale-like features, gill plates, and raised bumps for eyes. Those characteristics don't affect the lure's motion through the water or its appeal to fish, says Jones, but their effect on the bait's commercial success has been dramatic. After the new design was introduced late last year, sales of that lure more than doubled.

The jewelry effect isn't limited to hard lures. Just one example among many: Classic Fishing Products of Clermont, Fla., has been manufacturing a soft-plastic worm dubbed Culprit for 25 years. This year, they'll produce about 10 million of those faux worms, of which 98 percent will probably be used by anglers looking to land bass, says Mike Richards, a spokesman for the company.

The firm's best-selling worm is red--a color that bass actually can discern--and it accounts for about half of the sales of that bait, he notes. However, the company also offers the Culprit in 81 other colors or combinations as well. Six of those options--including Green Pumpkin Candy, Watermelon Silver Flake, and Grape/White Tail--were added just last year, and seven more were revealed in the company's latest catalog.

Newly offered colors typically sell well, says Richards. Retailers often specifically ask for those options because they know many anglers are eager to try new combinations of colors, even though the baits often don't resemble anything that a fish would normally see. "What's natural in life that's purple with green dots?" asks Richards. "Nothing, really."

And the gimmicks don't stop with bizarre color combinations. What can explain lures shaped like miniature beer bottles? Mermaids? Lures with NFL logos painted on them?

The Hall of Fame's Dzialo might have the answer: "I think most lures are designed to catch more fishermen than fish."
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Author:Perkins, Sid
Publication:Science News
Date:Apr 24, 2004
Words:2028
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