The importance of using scented baits couldn’t be clearer for catfish; they’re pretty much swimming tongues. The issue becomes slightly more complex with other gamefish, though. Studies have shown that olfaction plays a distinct role in finding spawning grounds and avoiding predators, but does using scented attractants actually help anglers? To a point, say fish biologists.
Smell and taste are the same underwater, and aquatic animals have evolved specialized features to perceive scented particles. Most fish have nares, the underwater equivalent of nostrils, in front of their eyes. The nares are each divided by flaps, which allow the fish to take in and expel water separately. Water is taken in as the fish breathes and is passed over rosettes, folded structures where smelling takes place. The folding of tissue in the rosette creates a bigger surface area, making more room for sensory cells, but there are big variations among the smell sensitivities of different species.
Fish like pike and muskie might have fewer than ten folds, but fish that rely heavily on smell – like carp and catfish – can have ten times that amount. These bottom feeders can have a sense of smell 1,000 times more powerful than other gamefish. This isn’t surprising, though, as walleye, pike, and muskie almost entirely feed by sight, and bass rely mainly on vibration.
Smell is a secondary or tertiary sense, and it becomes more important after a fish has detected prey – or a lure. The scent trail that is left in the water column makes stalking easier, and many times scent can convince a wary fish to bite. If the scent is right, that is.
The complex olfactory systems of fish have evolved to detect two things above all else: bile acid and amino acids. Bile acid is key component of a fish’s digestive system, and it is released in small amounts when fish feed. Smelling bile acid in the water is a sure sign to other fish that someone’s eating, and it usually triggers feeding for them, too.
Amino acids are the simple organic compounds that make up proteins. They’re present in all animals, and predatory fish have adapted to detect the specific amino acid combinations that signal food. No one amino acid is a winner; different species in different areas are attracted to different combos. If you are going to buy attractant, those that promise amino acids, bile acids, or natural flavors are the most likely to provide results.
Even using natural scents isn’t foolproof, though. Fish are surprisingly quick to make the connection between stimuli, especially when one of those is being ripped through the water and hoisted into the air by their lip. After a few experiences with scented lures or attractants, most fish will have learned to keep their distance.
That’s not to say that anglers should disregard scent entirely – if anything, it means the opposite. Multiple studies have shown that fish know to avoid lures that smell like humans. Taking a few extra seconds to rinse your hands of whatever you may have handled before getting in the boat – gas, potato chip grease, insect repellent, even soap – may mean the difference between a limit and being skunked.
Originally published in Outdoor News Minnesota