Cutbaits. Stinkbaits. Dipbaits. Hotdogs, cheesebait, chicken livers, Uncle Cooter’s-can’t-miss catfish concoction and an endless list of other home brews are used to lure catfish.
For many catfish anglers, at least those pursuing channels and blues, success follows those in the right place at the right time with the right smell or flavor.
So just how good are catfish at sniffing out your bait? Pretty darn good, according to some intricate and sophisticated studies.
Catfish detect chemicals in the water by smell and taste, and both senses are well developed. The two senses differ in the location of the sense organs and the part of the brain where the signals are processed, but both senses work the same in that a nerve cell fires when triggered by a certain chemical or family of similar chemicals in the water.
Olfaction — the sense of smell
The catfish version of a nose is a pair of olfactory pits on the top of the head into which water enters, flows through an elaborate surface area covered with sensory cells and exits.
Channel catfish can detect certain amino acids at concentrations of 0.17 parts per million to 0.00017 parts per million. Let me put this low concentration in more meaningful terms: Channel catfish can detect certain amino acids at concentrations as low as a teaspoon of chemical in a one-acre pond that averages 3 feet deep.
Channel catfish’s sense of smell has similar acuity to that of some mammals. I’m not talking about you and me: I’m thinking of mammals like whitetail deer that can sniff you out 100 yards downwind or that bird dog that can smell a quail 30 yards away.
Gustation — the sense of taste
Cells that function for taste are concentrated in the throat and on the barbels (aka whiskers) but, in fact, they cover the entire body. Taste receptors on the skin and barbels allow the fish to taste a potential food item without ingesting it.
Catfish can detect “biologically meaningful” chemicals by taste at concentrations as low 1 percent of what can be detected by smell, and catfish have the most-sensitive sense of taste known among vertebrate animals. Channel catfish are able to detect a couple of drops of certain amino acids in the one-acre pond mentioned above.
The range of chemicals catfish can detect is far from fully explored.
Above, I mentioned “amino acids” and “biologically meaningful” chemicals. Amino acids are small molecules that are the building blocks of proteins, so all catfish food sources contain amino acids. Thus, amino acids make good “real-world” chemicals for testing detection thresholds. They are also chemical molecules to which catfish have high sensitivity.
Detection of other chemicals, such as chemicals excreted by intact or injured fish, also allow catfish to zero in on prey. Different chemicals signal whether the prey is alive or dead.
Catfish can detect at least several different amino acids and, based on learning experiments, can discriminate among them. What is not clear is whether catfish can use chemical signatures — that is, the mix of different chemicals — to differentiate among food sources. However, differentiating different food sources might be unimportant, as blue and channel cats eat a wide variety of plant animal materials. And blue cats are notorious scavengers.
Lab studies have shown that catfish will follow a chemical gradient to locate the source. When an amino acid is detected, a catfish begins swimming toward to source, increasingly turning (presumably to decipher the direction of the source).
As the concentration of the chemical increases, the catfish begins biting and snapping, but only solid objects trigger swallowing.
Catfish are clearly able to detect changes in concentrations of chemicals and, thereby, follow a scent trail. But lab studies suggest you can have too much scent.
Although catfish live in a variety of water conditions, many live — and feed — in deep, turbid rivers where there is zero light and finding food is solely a function of chemical detection.
While a lot of attractant might lure catfish from a larger area in standing water or a greater distance downstream in flowing water, a large, dense cloud of your chemical attractant might also hinder them finding your hook because they are unable to pinpoint the source of the scent.
Now, would someone please tell me how long to age a box of chicken livers to make them work best?