Catfish Senses When it comes to senses, catfish are turbo-charged. Their sense of taste is unbelievable. Their sense of smell is unparalleled. Few fish hear as well, and catfish also have excellent sight and a superb sense of touch. On top of all that, catfish have other sensory abilities that seem more like science fiction than science fact. To say the least, they are highly attuned to the world around them. CATFISH are literally covered from head to tail with sensory organs.  The nostrils  lead to the complex olfactory pits. The barbels and most of the body are covered with taste buds. The back of the eyes  are coated with a layer of crystals that reflect light. The lateral line  detects vibrations in the water. Electroreceptive pores  cover the head region and the lateral line. SMELL. Catfish smell real good. Well, they don’t really smell good but they have an extraordinary sense of smell. Their smellers are right up front, in two little pits located in front of the eyes and behind the upper jaw. With this keen sense of smell they can detect food at long distances, but also in water where visibility may only be a few inches. Each olfactory pit has two nostrils, one for incoming water and one for outgoing water. These pits are lined with sensitive tissue wrinkled into a series of folds (below) to provide the maximum surface area for smelling. The number of these folds is related to sharpness of smell. Channel cats have more than 140. Rainbow trout have only 18, largemouth bass 8 to 13. Water is drawn into one nostril, over the sensory tissue and out the other nostril. Catfish detect some compounds at one part per 10 billion parts of water. If a substance is determined to be a potential food item, a message is sent to the brain telling the catfish to move toward the object for further investigation. TASTE. The catfish’s highly developed sense of taste is like something out of Ripley’s Believe It or Not. The smooth scaleless skin is completely covered with taste buds. A catfish just 6 inches long has more than a quarter million. On a giant blue cat or flathead . . . well, who knows. No one wants to count them. Imagine a huge swimming tongue. In a way, that’s what a catfish is. Most fishes’ taste buds are only found in the mouth – on the tongue, the palate and so forth. There aren’t that many of them, either. In catfish, the mouth is packed with dense concentrations of taste buds. The major flow of water is across the gills, so gill rakers facing water flow also are loaded with huge densities of taste buds. Taste buds are also found on the outside of catfish as well – their fins, their back, their belly, their sides, even their tail. On the flank of an adult channel or blue cat, there are at least 5,000 taste buds per square centimeter of skin. The highest concentrations on the outside of the body, however, are on the whiskers. Look at a catfish whisker under a microscope, and you’ll see a field of volcanoes. Every volcano is a taste bud. The taste buds function in two ways. Those covering the body help catfish locate food, even in dark, muddy water. They detect chemicals from nearby food that help the fish close in on the potential morsel. Then, when the cat is near, the long tapered whiskers are used as “feelers” to cautiously sample the food. If everything’s kosher so far, the catfish mouths the item. Taste buds in the mouth then determine whether the food item is edible. HEARING. Catfish don’t have ears, right? No, that’s not right. They don’t have ears we can see, but they don’t need them. They “hear” by receiving sound waves through their skin. Actually, a catfish’s ear is its swim bladder. That’s part of it, anyway. The swim bladder contains gas, creating an air space with a different density from the rest of the fish. When sound waves hit the bladder, it vibrates, just like our eardrums. This amplifies the sound waves, which then travel to small ear bones called otoliths in the inner ear. The otoliths start vibrating, too. As they vibrate, they bend little hair-like projections on the cells beneath them, which transfer a message to the brain. The swim bladder on most fish is independent of the inner ear. But in catfish, nature built a series of vertebral bones known as the Weberian apparatus, connecting the swim bladder and inner ear. Fish without these bone connections (bass and trout, for instance) detect sounds from about 20 to 1,000 cycles per second. The hearing of catfish, however, is much more acute. They hear sounds of much higher frequency, up to about 13,000 cycles per second. Low-frequency sounds that cannot be detected by the catfish’s inner ear are picked up by a series of little pores running along the fish’s sides, called the lateral line. Similar pores exist around the eye, down the lower jaw and over the head. Inside the pores are cells with little hair-like projections, similar to cells in the inner ear. These projections bend in response to water displacement, thus stimulating nerve endings that signal the brain. Catfish use this system to locate nearby prey, potential enemies and members of their own kind. Creatures scurrying across the bottom, flopping at the surface, swimming through the water or walking along a riverbank all create low-frequency vibrations in the water, which the catfish’s lateral line detects. Bullheads in particular are ultra-sensitive to low-frequency vibrations. The Chinese have used them for centuries to warn of earthquakes. Apparently, they can detect rumblings beneath the earth’s crust days in advance. Channel catfish raised in aquaculture ponds also exhibit sensitivity to low-frequency vibrations. They often rise to the surface in response to the footsteps of a person walking over to feed them. This behavior may be noted even when the person is 100 yards or more away! The lesson here: don’t bang around in your boat or stomp around on shore. One way or another, catfish will hear you. SIGHT. With their beady little eyes, it would seem catfish have poor sight. This is a fallacy. All our catfish have excellent vision. They frequently feed on live fish and use eyesight to capture this fleet prey. In clear waters, sight is probably the primary sense used to zero in on live forage animals. When you see a deer or raccoon in your headlights at night, their eyes glow from the reflection of light on a thin layer of crystals at the back of the eye, called the tapetum lucidum. This structure reflects gathered light back at the retina, greatly aiding night vision. Walleyes are probably the fish most known for having a tapetum. Catfish also have it but to a lesser degree. Scientists say rods and cones are present in roughly equal numbers in a catfish’s eye. Rods allow vision in dim light, and cones offer color vision in daylight. ELECTROSENSING. Perhaps the most amazing sense possessed by catfish is that of electroreception. Look closely on a catfish’s head and you’ll notice small scattered pores (below). These are sensory organs that detect electrical fields in living organisms. Electroreceptive pits also are in and along the lateral line. Thanks to these specialized organs, a catfish doesn’t have to see its prey or smell it or taste it or feel it; it can find its prey through electroreception, just like sharks. Every living cell is a battery. That is, if you were to stick an electrode inside a cell and another outside that cell, you would get a reading just as if you were measuring a battery with a voltmeter. Catfish can detect these electrical fields in their prey at very minute levels, the equivalent of detecting a flashlight battery at several thousand yards. With single small forage animals, however, the catfish must be very close – within an inch or less – for this method of detection to work. Work it does, though. This sense is extremely beneficial in dark muddy water or when cats are digging in mud or sand to find insect larvae and other invertebrates. The exceptionally powerful senses of catfish enable them to thrive in a wide variety of habitats. They cope better than other fish in difficult environments, and thus are often found where other fish are not. As catman Steve Quinn once put it, “Catfish can where other fish can’t.” The next time you feel a big catfish tugging on your line, think about how it found your bait. It will help you better appreciate the remarkable senses of these extraordinary fish.