Can Fish Smell?

How They Actually React to Lure Scents By JOHN N. FELSHER

F3-Lead

My dad used to say, “Companies make lures to catch fishermen, not fish.” True, every year, companies spend millions of dollars developing new “can’t-fail” scented baits they promise will catch more fish, but do they really work?

Unfortunately, most scents, like garlic, appeal more to humans than fish. Open a bottle of garlic-flavored additive in a room full of anglers and everyone immediately starts thinking about lunch as aromatic vapors fill the room. However, bass can’t detect aromatic vapors in the air any more than a scuba diver can smell a dead shark on the ocean floor. Moreover, if a bass could detect garlic, it wouldn’t automatically associate it with food.

Although the taste and smell systems in fish and humans share many similarities, people and fish simply detect chemicals in vastly different ways. People breathe in particles dissolved in the air and carried by air currents. Fish don’t breathe in air and cannot process airborne molecules. Fish can only detect chemicals dissolved in the water. A buffalo carcass could sit on a beach under a broiling Texas sun in August and fish would never find it unless some water-soluble chemicals spilled into the water.

Many anglers userattling baits, like this lipless crankbait, to attract bass. PhotoS: John N. Felsher, Larry Hodge

Many anglers use rattling baits, like this lipless crankbait, to attract bass. PhotoS: John N. Felsher, Larry Hodge

 

“Fish can detect small water-soluble molecules with both their taste and olfactory systems,” explained Dr. John Caprio, a Louisiana State University biology professor who spent decades studying fish neurobiology to determine how fish process taste and smell stimuli. “Humans detect volatile chemicals that dissolve in the air when we breathe them into our noses. Pour liquids up our noses and we can’t smell them. In the same way, fish can’t smell particles in the air.”

One of  the world’s leading experts in fish behavior relating to chemosensory  neurobiology, Caprio learned that the highly developed taste and olfactory systems in fish detect and analyze dissolved chemical stimulants in water much differently from how people process airborne smells and taste sensations. In his research, Caprio studied how different species of freshwater and saltwater fish instinctively react to specific natural chemicals they find in the water. He isolated some key chemicals that stimulate fish to feed and used that information to develop SCI-X, a feeding stimulant found in Attraxx soft-plastic lures (Attraxxbaits.com). When an Attraxx bait hits the water, it immediately begins releasing these natural feeding stimuli, exactly what a fish expects to find when looking for prey.

Largemouth bass rely primarily upon sight, not smell or taste, to find and attack prey. Bass react instinctively when they see a wounded minnow swimming with difficulty or a succulent crawfish crawling on the bottom. Therefore, bass normally hit artificial or natural baits that move.

“There’s no chemical in a fishing lure that’s going to attract a bass,” Caprio advised. “It’s the visual presentation of the lure and the mechanical movements that attract bass. Once a bass hits a lure, it will taste and feel it. If the object doesn’t have the right consistency and taste, a bass will spit it out, often long before the fisherman knows a bass hit the bait.”

A bass also uses its lateral lines like a biological sonar system to detect and analyze sounds and find prey by the vibrations they make. Sound wave vibrations move much more easily and for longer distances through water than through air. Because of its lateral line, a bass can detect a black worm dragged over a muddy bottom at midnight on a moonless night in dark water; but like scents, fish can’t detect all sounds.

Catfish use their barbels to sense food in the water. They also have sensors all over their bodies.

Catfish use their barbels to sense food in the water. They also have sensors all over their bodies.

“Many bass anglers use rattling baits that produce high-frequency sounds that humans can hear,” Caprio said. “However, fish hear low frequency sounds. Many lures give off sounds that are too high frequency for fish to hear.”

While companies making bass lures tend to create products that smell pleasant to humans, catfish bait manufacturers traditionally take the opposite approach. They sell baits that smell repulsive to humans, but ones they hope appeal to bottom-dwelling scavengers that habitually rely upon taste to locate food.

With highly developed sensory organs, catfish can detect very minute particles dissolved in the water. Like sharks, they may home in on those sensations from long distances. Nevertheless, even the most vile-smelling (to us) baits won’t attract catfish unless chemicals from that noxious mess dissolve into the water.

“A fish has a greater sensitivity to taste than a human,” explained Dr. Bill Carr, a retired University of Florida zoology professor who now works with the FishBites lure company. “Fish have taste buds on their lips, in their mouths and sometimes in the back of their throats. A catfish is like a giant tongue swimming through the water. It doesn’t just have taste buds on its barbels, but all over its body.”

In salt water and sometimes in fresh water, anglers occasionally dump fish oils into the water to chum up fish. They hope hungry predators detect the smelly substance and race in, ready to eat anything. However, oils do not dissolve in water; they separate. A fish may bump into an oily sheen in the water and possibly taste some components, but more likely couldn’t detect it. On the other hand, oily fish such as shad or mullet contain multitudes of chemicals in their bodies. Many body chemicals do dissolve in the water and attract predators looking for a meal.

Saltwater anglers often overestimate the effectiveness of oils in attracting fish.

Saltwater anglers often overestimate the effectiveness of oils in attracting fish.

“Often, an angler doesn’t realize that the receptors a fish uses to detect food have nothing to do with what the angler can see,” Caprio said. “Many baits release an oily trail in the water, which deceives the angler into believing that the bait must be working because the angler can see the oil. A chemical trail floating on the surface means that the chemicals are probably not water-soluble so fish can’t detect them.”

At worst, adding flavoring or scent enhancements can’t hurt, but adding the right chemicals could greatly enhance the attraction of a lure. The trick comes in thinking like a fish, not like a human and use what fish expect to find in the water when looking for food.