Studies have shown time and again that the voluntary release of big fish leads to a population of overall larger fish. One big female contributes far more viable, genetically superior eggs than a handful of eater sized fish, and her reproduction value will only ever increase as she ages.

The majority of modern anglers, fly fishermen and bass anglers especially, consider catch and release the most responsible form of fishing. While they are practicing a valuable conservation technique, they may be unknowingly creating harder-to-catch fish.

Fisheries biologists and anglers alike have long wondered if fish can learn to avoid lures. Current research says yes. When presented with a hookless minnow imitation, bass in a lab will initially strike fast and often. After a few swipes, though, the bass learn to ignore what is now obviously not food. That’s without even associating the lure with being hooked in the lip, yanked through the water column, and hoisted into the air. The same general response is seen in Northern pike, Muskie, salmonids, and sunfish. More research is being done on other game species.

Recent studies in Minnesota, Wisconsin, Nebraska, and Florida have focused on observing this behavior in heavily pressured lakes and rivers. Biologists have noted that fish catchability is highest immediately after a body of water is opened for fishing. It doesn’t matter what anglers are throwing – the fish are biting. This trend steadily decreases over the next two months as the fish become familiar with the most popular presentations.

And unfortunately, fish don’t actually have that famous three-second memory. When those same lab bass are exposed to the minnow lure again after a rest period, none react as strongly to it as they did initially. After a few inquisitive strikes, the bass return to ignoring the lure. Unsurprisingly, when bodies of water with a history of high angling pressure are closed for a few months and then reopened to fishing, the fish don’t act like those who have never been caught before. After a brief period of increased catchability – though not nearly as high as observed in historically unfished areas – fish become just as hard to catch as they were before the season closed.

Only populations that are regulated by catch and release exhibited this trend. Species that experience the highest levels of harvest did not become harder to catch as angling continued, which further supports the hypothesis that fish learn by experience to avoid lures. Luckily, biologists suspect that any social learning is minimal. Seeing another fish caught on a hook is not likely to dissuade another from striking as well.

After being caught, released fish flee to dense cover and are significantly less likely to be caught again. Fisheries biologists report that these wary fish can quickly learn the difference between big, bright lures and their everyday forage. They’re not so adept at picking out smaller, more natural colored lures, though.

To outsmart these skeptical individuals, first find the areas in which you’re guaranteed to lose a few lures: dense weeds, stump fields, and brush piles. Then dial down your lures to the smallest, most natural options. The closer you are to matching the hatch, the more likely you are to fool an experienced fish. There doesn’t currently seem to be an advantage to either fishing fast or slow, so let the temperature and weather conditions direct you in that regard.

Targeting pressured fish is undoubtedly frustrating, but that’s what makes catching trophies that much more satisfying. Knowing that you’ve not only fooled a fish that’s spent over a decade learning to avoid a hook and line, but that you’ve strengthened the population by releasing it, is the ultimate reward.

Originally published in Outdoor News Minnesota