VISIT the fishing section of a sporting-goods store and there will be an array of smelly, flashy, noisy things which claim to be irresistible to nearly any species of fish. These high-tech baits and lures have become big business: American anglers spend more than $2 billion on all types of kit each year. But does their investment yield much more than fishermen’s tales?

It seems it might. Fly fishermen have been imitating insects for centuries by tying coloured feathers and thread around hooks, and firms like Northland Fishing Tackle of Bemidji, Minnesota, produce the same lure in dozens of different patterns. Whether this variety exists to attract the fish or the fisherman has been the subject of much debate.

The difference between watermelon-red and bubble-gum pink might actually matter, says Culum Brown, who studies fish cognition at Macquarie University in Australia. Water selectively absorbs different wavelengths of light, so reds can disappear within ten metres (33 feet). But many shallow-water species have highly evolved visual cortexes and their eyes can contain up to eight different light-absorbing photopigments, compared with the paltry red, blue and green which humans possess. These extra light receptors give fish increased sensitivity to other wavelengths; some species can even see ultraviolet light, which is invisible to humans.

For certain species, however, smell can be more important than looks. The diffusion of scent molecules occurs much more readily in water than in air, which gives some fish a sense of smell over 100,000 times keener than humans. Keith Jones, a researcher in Spirit Lake, Iowa, working for Pure Fishing, a tackle producer, has decoded what some freshwater game fish are sniffing for. His team began by dissecting small prey like minnows and crayfish, and identified the most prevalent molecules in different regions of their anatomy. Then they synthesised these compounds in the lab and tested them to see which elicited the strongest response from predator fish.
For certain species, however, smell can be more important than looks. The diffusion of scent molecules occurs much more readily in water than in air, which gives some fish a sense of smell over 100,000 times keener than humans. Keith Jones, a researcher in Spirit Lake, Iowa, working for Pure Fishing, a tackle producer, has decoded what some freshwater game fish are sniffing for. His team began by dissecting small prey like minnows and crayfish, and identified the most prevalent molecules in different regions of their anatomy. Then they synthesised these compounds in the lab and tested them to see which elicited the strongest response from predator fish.

Casting wide

The tricky part was the delivery mechanism. The polymers used to make artificial bait in the form of rubbery worms did not mix well with the scent and hindered its diffusion into water. Dr Jones solved that problem by developing a proprietary polymer in which to embed the molecules, which boosted scent diffusion over 400-fold. His worms have been selling like smelly little hot cakes ever since.

For other types of bait, swimming skills are paramount. Fishing lures use a variety of control surfaces to move through water, ideally mimicking the movement of distressed prey. Dr Jones and his colleagues built a large underwater racetrack to tow different lures through schools of hungry fish, and then tested the most frequently nibbled in the underwater equivalent of a wind tunnel. Using high-speed photography they were able to quantify attributes like pitch, yaw, roll and oscillation frequency to determine the movements that attract different species of game fish.

Yet even the best lure is useless if it is alone in the water. The latest fish-finders combine different ultrasonic frequencies and beam angles to probe the water around a boat. Some generate photo-like images of the bottom, including structures such as sunken trees and pilings which are often prime habitat. With the click of a cursor, an angler can differentiate between game and baitfish, calculate their distance from the boat and estimate which bait is best according to the water conditions.

“It is really getting kind of unfair,” says Macquarie’s Dr Brown. “If you are going to use GPS to take you to a location, sonar to identify the fish and a lure which reflects light that humans can’t even see, you may as well just go to McDonald’s and order a fish sandwich.”


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