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Why do fish seem to want a particular lure one day, then switch their preference to something else the next? We fishermen might simply say, “Because they’re fish,” and take our lumps.

Fishery ecologists have a more established model to go by. They explain the fickleness of fish on the basis of what they call the “optimal foraging theory.” Understanding how it works might help you get more bites.

There is nothing complicated about this commonsense theory. Food (forage) provides energy, but searching, catching, handling and ingesting food expends energy. According to the optimal foraging theory, the best choice of forage is the one that provides the greatest net energy. But are fish capable of making feeding choices based on maximum energy gain?


Some years ago biologists who wanted to answer that question placed bluegills and blue tilapia, which have a profile very similar to that of bluegills, in tanks with largemouth bass. The tanks were stocked with carefully selected bluegills and blue tilapia that had the same body length and depth. When vegetation was present in the tank, the bass ate the tilapia. That makes sense: Bluegills are adept at hiding in water weeds, whereas tilapia tend to stay in open water, making them easy pickings.

What was really interesting about the experiment, though, is that when vegetation was completely absent, the bass still preferred the tilapia. Although the bluegills and tilapia were of the same length and body depth, the tilapia were thicker bodied and weighed more, inch for inch. The scientists drew the conclusion that when both prey were equally vulnerable, bass selected the one that would provide them with the greater amount of energy.

The optimal foraging theory suggests that when you’re fishing for bass that are in ambush mode, a bigger, bulkier bait will draw more strikes than a smaller one. This explains the success of bulky baits such as jigs, creature baits, lizards and oversize tubes for flipping heavy cover or working dense weed beds.

The same rationale can be applied to topwater baits. Largemouths and smallmouths often demolish big topwaters but ignore smaller offerings. The bass have that bait trapped. Energy expended to capture the bait is minimized.

Conversely, downsizing might be wise when fishing open water with a fast-moving crankbait. Since the swimming speed of a fish correlates to its body length, the bass might perceive the smaller lure as something that requires less energy to capture.

There is no substitute for time on the water to help improve your catch rate. But understanding basic biological principles that affect feeding behavior can give the novice angler a good starting point and help the veteran angler make sense out of a lifetime of experience.


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