Biological Keys to Triggering a Hot Bite
Watching crappies move under water -demonstrates their cautious deliberate style that makes, at times, for the fastest fishing imaginable. Other times they leave us baffled, wondering where they went or why they won’t bite.
When hungry, crappies scull along, seemingly measuring the distance between their mouths and a preyfish. If prey is close enough, they may swoop in and vacuum the minnow, or else try to inch closer without causing it to flee.
In clear water, like in our giant -In‑Fisherman aquarium and in many of the clear natural lakes of the North Country, where scuba observation and underwater camera viewing conditions are ideal, crappies use vision to find and catch prey. But at what range can crappies see, and can they detect colors?
And what about the murky rivers and reservoirs that are also home to crappies? Where do a fish’s other four senses fit into the feeding strategy? A look at the way crappies sense their world provides clues to more effectively finding and catching them in all sorts of conditions.
The eyes of crappies are among the largest for their body size of all freshwater fish, a feature that alone suggests the importance of vision to both crappie species. For fish and other animals, what is not needed usually isn’t present. Occasionally, a feature is a throwback to an earlier ancestor and is obsolete. But for fish, intense predation pressure tends to shape a critter to fit its environment.
This assumption is helpful when describing the sensory world of the crappie, including its vision. Little research of the sensory systems of crappies has been done, surprising in that crappies tame quickly, live in confined quarters, and are easily handled. As a result, much of what we think we know about crappie vision and their other sensory systems is based on research with other species, usually trout and goldfish, but sometimes other members of the sunfish family. Crappies are closely related to sunfish and bass, and likely are similar in many sensory respects, but undoubtedly different in subtle ways we can only guess at.
Visual Range: As humans, it’s difficult for us to imagine vision in any way other than the way we see. Yet the watery medium is far different and puts serious limits on vision under water. Fish eyes are similar in form to ours, with a cornea, iris, lens, and retina. As with vision in air, underwater vision depends on the detection of light of different wavelengths.
These same wavelengths enter water but are absorbed, reflected, or scattered before traveling nearly as far as they do in air, a much purer medium. In an ultraclear lake, blue and violet penetrate deepest, beyond 50 feet. But in more typical water that’s stained by suspended particles and various, greens, yellows, or reds penetrate deeper. Yet the more algae and suspended particles, the shorter the field of view, both looking into the water and viewing from below.
The length of a fish’s visual field depends on water clarity and is generally similar to a Secchi disc reading, a simple water-clarity test. The Secchi depth is the depth that the black-white disc disappears when lowered into the depths during prime viewing conditions (bright sun, relative calm). So with a Secchi depth of 10 feet (considered clear), a fish’s visual field in the upper layer of water would extend about 10 feet in front of its snout. And field of view shrinks with depth.
Fish vision expert Dr. Don Quick has likened a fish’s vision to walking into a thick fog during daylight. Above, the sky looks white and white surrounds on all sides. It’s impossible to make out dark objects in front of you because the light entering your eyes is reflecting off fog droplets closer to you.
As you move closer to an object like a tree, it becomes dimly visible, growing more distinct as you near it. Standing just inches from the trunk, the tree looks as it would in clear conditions. But branches several feet above are still obscured by fog. Like a person in fog or in a smoky room, a crappie sees close objects clearly but more distant objects as though in a perpetual fog.
Crappies like to inspect objects closely, and this characteristic should be a guide to your crappie fishing. A crappie, interested in an item, either by vaguely spying its shape from several feet away (farther in clear water) or else detecting it with another sense, often closes in for a better look. If the object is moving fast like a crankbait, it’s likely already out of range. But if it’s nearly motionless, jiggling along, or slowly moving vertically, it may be fair game, being of the right size and with an appealing profile.
The forward and upward position of crappie eyes suggests the preferred direction for feeding—ahead and somewhat above the snout. A bait in this position attracts the attention of one or sometimes many crappies that rise to inspect it more closely, or sometimes engulf it in a rush if they’ve put on the feed bag.
As fish approach a target, they focus their eyes with specialized muscles that move the lens of the eye forward and backward, a process called accommodation. The lens is retracted for scanning a distant background, then pushed forward to inspect a close target, like the zoom lens on a camera.
These physical and behavioral characteristics associated with vision suggest the use of a float for crappie fishing, to suspend lures or livebaits at a level slightly above the depth at which fish are holding. As crappies shift vertically, in response to light, baitfish, or other factors, float adjustment keeps the offering in the best position. Floatfishing with small jigs or livebaits is a staple presentation for crappies throughout the year, though other options complement it.
Color Vision: Crappie eyes have multiple cones, light receptors used in bright light to differentiate wavelengths of light that equate to colors, giving evidence of color vision. -Further evidence arises from tests with the closely related largemouth bass, bluegill, and green sunfish, whose color detection has been verified in lab tests. By studying the characteristics of the cones of a species, physiologists can make educated guesses about the colors the species is most sensitive to.
Human eyes have three sets of cones, each most sensitive to a particular color, and the cones compare the amount of stimulation from longer wavelengths (red, orange, yellow), intermediate wavelengths (-yellow-green, green and blue-green), and short wavelengths (blue, and violet). Largemouth bass have two sets, thought to give more sensitivity to colors in the red-orange range, with less sensitivity for yellows and grays. Bass and sunfish can, however, sense colors of the entire spectrum, to some extent.
Little study of bass vision has been done, and to my knowledge, no experiments have tested crappies. Color sensitivity is therefore purely speculative, and its effects on color choice in jigs is even more of a stretch. Suffice to say that in clear, shallow water, crappies probably can discriminate chartreuse from yellow or white, orange from red shad, or pink from nuclear chicken.
In murky rivers, stained impoundments, or fertile ponds, color vision is lost at depths around 10 to 15 feet, depending on clarity and light levels. Fish switch from reliance on color–sensitive cones to rods, receptor cells that detect black and white and shades between. The last color to remain visible is one that matches the general water color of the lake.
Crappies apparently see well using their black-white vision capability, for they feed extensively after dark during all seasons. Their large eyes may gather more available light than the eyes of small preyfish, placing crappies at an advantage. They also take advantage of the typical vertical migration of plankton, which move toward the surface after dark and recede at first light. Dense plankton draw preyfish, and crappies school below the plankton to feed heavily.
Most fish are thought to have a functional sense of hearing, based on the structure of their inner ear and on behavioral tests with some species (not crappies). Early on, ichthyologists considered fish deaf, as no external openings to an ear were apparent. In recent centuries, though, dissections revealed an inner ear structure analogous to ours, with tiny ear stones, sensory cells, and semicircular canals for balance.
Under water, external ears would cause water drag and hurt swimming speed, though that might not be a problem for a crappie. Fish would look more than a bit comical but we’d get used to it. Primarily, though, we and other terrestrial animals use external ears to funnel sound into the inner ear.
Underwater sounds travel so far and so fast (almost five times faster than in air) that fish are surrounded by sound. That’s because water molecules are much more closely packed than air molecules, and sound waves cause compression waves that travel along underwater until they contact an object. Fish don’t need a middle ear, used by terrestrial animals to transduce airborne sound waves to the liquid medium of the inner ear.
When sound waves contact a crappie, they pass through fish flesh, which is about the same density as water. Inside the inner ear, however, the waves can’t move the dense calcium carbonate otoliths (ear stones) at the same rate, and the difference in motion stimulates the sensory cells of the inner ear, resulting in hearing as the impulses are sent to the central nervous system.
Minnows and catfish have the widest range of hearing, from a low-frequency range of about 10 cycles per second (cps) to as high as 13,000 cps in some catfish species. Fish that lack swim bladders, such as sharks, rays, and lampreys, have the poorest hearing. Crappies and other sunfish, and members of the pike and perch families, are intermediate in hearing range.
The swim bladder acts as a resonating chamber. In fish like catfish and minnows, the swim bladder is connected to the inner ear by a special set of bones called Weberian ossicles. This physical connection allows a greater range and probably also more sensitive hearing.
Tests with related species suggest that crappies probably detect frequencies from just about 10 cps to perhaps 1,000 cps with their inner ear. Those below about 200 cps are detected by both the inner ear and the lateral line, a separate but related sense.
Lower frequency sounds travel far under water, attenuating only slightly compared to sounds in air, unless physical barriers are reached. So crappies likely can hear a loud and distinct underwater sound from a distance of more than 100 feet. Under water, as in air, background sounds tend to blur a sound’s effects, and fish probably tune out a din of normal sounds.
While rattling lures are the rage for bass and walleyes, few crappie baits have this feature. Most crappie jigs are too small to house a rattle chamber, though some small plastics can accommodate a thin glass rattler. At times, small rattling crankbaits catch lots of crappies, but the role of sound can’t be separated from the underwater vibration the lures create, or their appearance.
We have little practical experience with using sound to attract crappies, but what we do know suggests that sound should work to alert fish that something is in the area. An active crappie might approach the sound, though directional hearing is poor in fish. An inactive fish might ignore the sound or be frightened.
Small rattles attached to jigs or inserted in plastics produce sound that’s easily heard with a hydrophone suspended in a tank. But sound is produced only when the jig hits bottom or an object, or is vigorously shaken. Rattle shapes and materials seem to affect the frequency of the sound as well as its volume.
This sense, exclusive to fish and aquatic amphibians, takes advantage of the power of low-frequency sounds in water to provide more information to the animal. Fish use their lateral line, a series of pores connected to an interior canal that runs down each side, to detect movement caused by objects displacing water, like predators, prey, or school mates. They also can use it to detect threatening objects like boats and trolling motors.
Lures that move slowly or that barely twitch can be felt by a crappie via its lateral line. During daylight in clear water, vision may guide most crappie feeding. But at night or in murky water, limits on vision suggest that the lateral line provides cues that help fish feed, avoid danger, and navigate obstructions like brushpiles.
The irregular beat of a wounded minnow’s tail is probably a universal attractor for predatory fish. Similar actions with plastic baits or feathered jigs also may attract feeding fish or cause them to engulf a bait. The fact that crappies often eat tiny prey like barely visible zooplankton suggests that, at times, the most subtle presentations may be best.
A close look at a crappie’s snout reveals a pair of nostrils or nares, as they’re called in fish. You can see the front opening where water enters the olfactory chamber, and the rear port where it exits. Inside each chamber, water washes over the feathery olfactory organ, where sensors detect substances that compose all living matter and much that isn’t. These building blocks are known as amino acids, and many lab tests have been done with certain fish species, but apparently not with our friend the crappie.
Tests show that some fish are far more sensitive to water borne materials, with eels generally considered the keenest sniffers, capable of detecting pure substances diluted to just a few parts per trillion. Minnows, salmon, and trout also are sensitive, and for different biologically significant reasons. Salmonids use olfaction to imprint on their stream of birth before departing to feed in the ocean. Upon -returning to spawn, they follow the scent trail for many miles to locate an appropriate spawning site.
Minnows, on the other hand, use olfaction to sense danger, and individuals emit a chemical alarm pheromone called Schreckstoff when they’re struck, alerting fellow members of the school to the danger. Recent studies have found that pike are attracted to Schreckstoff and may locate a feeding area and join in. We don’t know if crappies can do this.
Many commercial fish-attracting formulas are available, containing either mixtures of proteins and amino acids, processed preyfish or crayfish, or other natural materials like anise, salt, or garlic. Experience with several types suggests that these sprays and pastes may enhance a slow presentation in certain conditions, particularly when fish are holding in one spot and rather inactive, typically in cold water.
It’s unlikely that crappies can follow a scent trail for any distance, as water dilutes a substance so quickly. But at close range, natural juices from a minnow or maggot might well encourage a bite from a reluctant fish staring at it from a foot or two away. Applying scent products to plastics and hair jigs may turn a looker into a biter.
Like smell, a fish’s sense of taste occurs in a medium where molecules are dissolved in water. As a result, it can be harder than in the terrestrial environment to distinguish whether olfaction or taste is responsible for a reaction. That’s particularly true for fish with taste buds all over their bodies, like some catfish. A fish’s taste buds are microscopic nipple-like structures densely packed in localized areas, sometimes 10 to 20 buds per square millimeter.
Catfish can taste substances from a distance, though a much shorter distance than they can detect by smell. Experiments show that trout, who lack barbels or taste buds on their bodies, also can taste from a distance. The crappie has taste buds on its mouth, tongue, and throat, plus the outside of the mouth. It also has a palpatory organ on the roof of the mouth, located just behind the front teeth.
Taste is important to all fish, the sense that distinguishes dinner from disaster, often the final barrier between fish and fisherman. A crappie can inhale a bait, decide it’s objectionable, and eject it in less than half a second, far faster than the most wired angler can set the hook. They do this with startling frequency, and the action must be observed underwater or in an aquarium, as the rod won’t twitch and even the tiniest bobber barely jiggles.
In nature, 20 common amino acids exist, plus a few exotic ones. Different fish species favor different amino acids and combinations of amino acids. Experiments at the Pure Fishing lab have fostered the production of several species-specific flavor formulas that have been impregnated into soft plastic lures to encourage fish to hold them longer.
Tests on crappies found them to be the most finicky of our popular gamefish, while rainbow trout were the least selective. Crappies only seemed to savor two or three of the many flavors the researchers offered, a far narrower taste spectrum than that of bluegills and bass. Crustacean and baitfish -flavors worked best.
Flavors found in favored natural foods are attractive, but packaging essence of minnow, Daphnia, or mayfly into a lure is a challenge, given the need to preserve a food while maintaining its basic flavor. Several softbaits and pastes are infused with natural food substances, however.
Other attractive flavors aren’t usual fare for fish. Many species flock to garden worms and nightcrawlers, though they’re not a common prey, and gamefish in arid reservoirs probably never see them. Pike sometimes prefer mackerel, though they never encounter this marine species.
Experiment with new artificial formulas and add-on flavors, as well as essences of natural food. Several new flavor formulas have a viscous consistency that clings to a bait for almost an hour in cool water. Livebait can give an edge in tough conditions; carefully hooking the bait can help flavors leach out.
With waxworms, eurolarvae, or other maggots, nick the hook point through the head or tail of the bait, not puncturing organs. That way, body fluids escape gradually from the wound, while the larvae remain alive and active for a time. Nick the hook into the lips of minnows or into the back above the spine.
Making a Sensible Presentation
Special treatments that target specific sensory capabilities of crappies are warranted anytime fishing is tough. Try sensory tricks when you find your favorite crappie hole crowded with boats. Unless you surrender your spot, the challenge is to distinguish your presentation from the crowd.
Light line and light hooks can give a visual edge, hiding the presentation and allowing a livebait to live longer and move more naturally. Fluorocarbon lines with ultra-low visibility are great in these conditions, too.
Jigs with special shapes and colors can provide a visual advantage, sometimes a huge difference in crappie fishing. Plastics and feather bodies can match baitfish colors, or increase visibility with chartreuse or white-pink combos.
Try rattles and vibrating baits to appeal to hearing and lateral line senses. But remember that mimicking the smooth movements of small minnows may best stimulate the lateral line sense of crappies.
We await further studies on the sensory physiology of crappies, to provide more precise knowledge about the way they sense, see, and feel. In the meantime, we consider the constant array of information passing into a crappie’s tiny brain and marvel at the way fish take it all into account to live, grow, and reproduce. ■