Considering the fact that civilized humans--humans at least bright enough to seek shelter in caves--have been on Earth for 50,000 to 100,000 years, you might think we'd have this business of fishing down pat. Fish do have the advantage of time, though, because they've been around for an estimated 400 million years. On the other hand, they still have a brain about the size of a pea. And it's not much of one, being pretty much an enlargement of the spinal cord.

Ironically, that itself is a clue as to why catching a fish isn't a simple and straight-forward process. Fish are slaves of their senses; they don't ponder abstracts and permutations like humans do, they react to various stimuli. If you've ever been around a four-year-old when he or she hears the jingle of a nearby ice-cream truck, you've already grasped this concept. Also, the stimuli that fish react to are very different from those that you and I react to (and I refuse to write a simile or metaphor about that, because fishing is a wholesome activity). But the point is that it can be difficult to catch fish consistently if you don't understand, say, how the heck they can live in water in the first place. This chapter introduces concepts that can help you become better at catching fish.

Hal's Story: A Day in the Life of a Fish
Hal (not his real name; he doesn't have a name) is a foot-long largemouth bass who lives in a 100-acre lake in a state with a moderate climate. Hal was born in the lake three years ago, one of about one thousand fertilized eggs that hatched in late spring. When he was an inch long--by which time more than half of his nestmates had been eaten by other fish--he was on his own, seeking shelter in the weeds of the cove where he was born. Hal has spent most of his life in that cove, leaving it only when the water there became too warm, too low, or too cold.

At sunrise this summer morning, Hal is hovering just inside the edge of the bed of lily pads that extends 10 feet from the shoreline. His belly is full of various minnows, insects, and one unlucky frog that Hal ate during the course of the previous night. Hal roamed the entire cove finding this forage, but now he is staying under the cover of the lily pads, avoiding the direct sunlight.

A school of 3-inch long shiners, a dozen in all, swims past the edge of the lily pads, looking for insects and any tiny aquatic creatures that will fit into their minuscule mouths. Hal sees the school and remains motionless. He will not go after the school and expend energy chasing them. However, the last shiner in the school is a bit smaller than its mates and must swim harder to keep up. This effort sends vibrations through the water that do not synchronize with the vibrations made by the rest of the school. Hal waits until the shiners are almost past him, then darts out and opens his mouth behind the last shiner. By this time the entire school has sensed the presence of the predator and has begun swimming quickly toward the deeper water of the cove, but already the last shiner is in Hal's mouth. Hal turns the shiner around in his mouth and swallows it headfirst while swimming back to his station in the weeds.

Hal remains there for a couple more hours, eating one more shiner in a similar manner. By now the sun is higher in the sky and Hal moves to a deeper, and thus cooler and darker, section of the cove, where he is more comfortable and less likely to be seen by predators. Hal stays in the depths for most of the day, moving around close to the bottom, finding and eating two small crayfish.

Hal's Evening
Toward dusk, when the sun is off the water, Hal moves back to the lily pads. A not-quite-grown green frog jumps off one lily pad and begins swimming toward another. The sight of the frog and its vibrations trigger Hal into movement. He rises to near the surface, studies the frog for a few seconds, and with one powerful burst shoots up and out of the water, grabbing the frog in his mouth in the process. He swims back down and swallows the frog, again headfirst.

Minutes later something splashes down on the water in almost the same place where Hal captured the frog. Again, Hal is triggered into movement, but as he rises near the object, it moves in a most unfrog-like manner, moving way too fast through the pads, at one point sticking to a pad stem and making it quiver and shake. Hal moves quickly away from the object disturbing the environment and leaves the lily pads altogether, dropping down to the bottom of the cove.

The fisherman standing on shore yanks on his fishing rod, eventually disentangling his lure from the weeds, reels up, and casts again elsewhere.

Cautious Casts
Some fishing lures are good at catching fish, others are good at catching fishermen. When you're buying lures, don't fall for fancy packaging or ornate designs. A good lure either imitates the natural forage of the water you intend to fish--long, slim, silver minnows, perhaps; or small crayfish--or will provoke a strike because of its action in the water. (More on lures in Chapter 11, "Lures: Virtual Reality to Fish.")

The sun sets. That night Hal moves around the cove again, searching for shiners and other small fish. A cricket falls into the water just inches from the shoreline and Hal, being only a few feet away, blasts into the shallows to eat it. Later, a field mouse swims across the water and Hal rises up, studying the rodent. But suddenly a bass nearly twice as big as Hal appears from the other side of the cove and engulfs the mouse in a shower of spray. Hal moves off, and as the light from the early morning sun hits the water, goes back to the refuge of the lily pads.

Loose Lines
Many people, even experienced anglers, assume that a fish will hit a bait or lure because it's hungry. This is true most of the time, but certainly not always. For example, fish that are protecting their nests of eggs or young will often attack a lure retrieved past them, only to defend their progeny. And certain species of fish, like shad and some salmons, that migrate up a river or stream to spawn (mate) sometimes aggressively hit an angler's offering. But if you open a migrating shad's belly, you'll find it empty. When spawning, these fish hit lures only out of reflex.

Just Another Survivor ...
Hal's life may not seem to be a particularly pleasant one because everything he (and every other fish) does revolves around survival: eating; competing with other fish for the same food supply; locating to various parts of the water to avoid extreme cold, heat, or light; and staying away from predators (reproduction, another survival instinct, will be covered later in this chapter). Hal's life is not a Disney movie; anthropomorphizing may be fun but it won't help you catch fish. Hal isn't cagey or crafty or plotting; he is simply a survivalist.

He is also quite tasty when filleted, dipped in milk, rolled in flour, and fried to a crispy golden brown.

Fish Physiology 101

Fish are cold-blooded (meaning their body temperature is not internally regulated) vertebrates (meaning they possess a spinal column) that live in waters the world over. About 17,000 species of fish are now known.

There are two basic biological groups of fish: bony fish, which have skeletons made of bone and are the quarry of most fishermen; and cartilaginous fish, which have skeletons made of cartilage. The latter group consists mainly of sharks, rays, and skates, found primarily in salt water. The females of most bony fish discharge their eggs into the water, where males fertilize them with their milt(semen). The eggs of cartilaginous fish are fertilized in the female's body.

Bony fish share many characteristics, as indicated in the following illustration.

3.1. The basic anatomy of a bony fish, using this large-mouth bass as an example.

Most bony fish have two sets of paired fins: the pectoral fins, which are typically located just behind the gills; and the pelvic fins, found on the fish's belly below the pectoral fins. There are also three vertical fins: the dorsal fin, which is on the fish's back (some fish have front and rear dorsal fins); the anal fin, which is at the rear of the belly, and the caudal fin, which is the tail. Fins provide mobility and balance.

Fish must take in oxygen from the water and eliminate carbon dioxide from their circulatory systems. This is performed via the gills, which bring the fish's blood supply in close contact with the water. Bony fish have four pairs of gills, which are located on either side of the fish just behind the head. A fish "breathes" by closing the gill slits and opening its mouth, taking in water. The water is then forced through the gill chambers, over feather-like gill filaments that absorb oxygen from the water and remove carbon dioxide from the blood. The water is then passed out through the opened gill slits.

The skin of a fish is covered with a thin layer of slime, which performs a number of vital functions. First, the slime serves to protect the fish from parasites and disease. Second, it allows the fish to move easily through the water (which is why some long-distance swimmers coat their bodies with grease before a competition). Third, the slime prevents water from entering the fish's body.

Getting the Point
An anadromous fish is one that migrates from the ocean to a freshwater river to spawn, such as shad and striped bass. Salmon that have been transplanted to the Great Lakes still exhibit this behavior, moving from the lake to a tributary to spawn. Fish that migrate from freshwater rivers to oceans in order to spawn are called catadromous fish.

Beneath the slime on most bony fishes are scales, which serve as another form of protection. Scales are layered in rows on the fish's body, much like shingles on a roof. One edge of each scale is attached to the skin of the fish. Scales are not living tissue, somewhat resembling fingernails. Some fish species have no scales; some have tiny, practically invisible scales; and some have large ones. People who eat large-scaled fish like perch with the skin on, such as when baking, should remove the scales before cooking. This can be done with a scaler, which resembles a dull-edged, large-sawtoothed knife. (See Chapter 29, "In the Pan or On the Wall?" for more information on fish cleaning and preparation.)

The lateral line on a fish is a long, thin canal that runs horizontally on each side of the fish's body, from just behind the gills to the base of the tail. On some fish it is also continued on the head and may have numerous branches off the main line. The lateral line is filled with sensory organs with which the fish is able to detect low-frequency sounds and changes in temperature, pressure, and water current. Fish also possess an inner ear, and numerous pits on the skin containing nerve endings detect touch. All this makes for a very vibration-sensitive creature.

Fish taste things via specialized taste organs located in and around the mouth. Fish may also be able to detect taste via additional organs on their body. A number of species, such as catfish, have barbels(commonly referred to as "whiskers"), or thin protrusions emanating from the mouth area. These are very sensitive to taste.

Fish smell (that is, they are able to) via nostrils on either side of the head. Nerves connect the nostrils to the brain and allow the fish to search for food. Some fish, most notably sharks, have highly refined senses of smell and rely on it more than they do eyesight to find food. Some fish use their sense of smell to find particular waters. Anadromous fish such as salmon live in oceans but always migrate to the stream in which they were born. Their senses of smell allow them to detect the odor of their home stream.

What Fish See and Don't See
Fish see things very much like humans see things, although there are some important differences.

First, with the exception of some sharks, fish don't have eyelids and tear glands. Because the fish is in constant contact with water, there is no need to rewet the eye and clean it.

Second, most fish can't regulate the size of their iris, which is the colored ring on the eye. The human iris can widen or shrink to adjust to the amount of light, leaving just a dot in the center when the light is bright, or exposing the whole lens in dim conditions. Fish, therefore, must move to different areas of their environment to adjust to the amount of light in the water. (Of course, light under water never reaches the same brilliance as does light above it.) This is why fish rarely expose themselves to bright sunlight.

Third, the lens of a fish is round (when looking from the side), not disk-like as in humans. Fish focus on objects by altering the position of the lens, instead of changing its shape, as we do.

Fourth, because fish have eyes on either side of their head, they can see objects to either side of them simultaneously (although most fish can't focus on the same object with both eyes). This also means, however, that fish have a "blind spot" directly in front of their heads, because the line of vision from each eye intersects at a certain distance in front of them?from a few inches to a few feet, depending on the fish.

Fifth, some fish species are farsighted, some are nearsighted; others have no problem focusing on both distant and close objects. This last group can focus their eyes independently on different objects at different ranges as well. Authorities agree that the various vision capabilities of fish depend on the environment and habits of the particular species. For instance, a bottom-hugging catfish has no need to see objects at a long distance; the fish is suited to living and feeding in dark and often silty waters. This makes perfect sense when considering that catfish have those taste organs on their barbels, which allow them to identify food without having to get a clear picture of it. Conversely, brown trout--which often feed on insects floating on the surface of the water--need good long-range vision to search for and identify forage.

Fish see color very well, at least as well if not better than humans can, and can distinguish contrasts, brightness, and shade. This holds true mostly for comparatively shallow-water species. Because light does not penetrate water very well, fish that live in the depths have no need to distinguish colors, as most aren't visible there anyway.

School Notes
Because fish don't like bright light, casting to large areas of shallow, sunlit waters is usually wasted time. This is one reason why dawn and dusk are usually good times to fish. Also, if you can easily see a fish, that means it can also see you, and any sudden movement will scare it into hiding. Back off slowly and cast from a distance.

Where Fish Live
Different species of fish prefer various types of habitat, depending on their biological needs. Often, that habitat is determined by the temperature of the water. Because fish cannot internally regulate their body temperature, they must seek water in which they are comfortable.

Brook trout, for example, require very clean, cool (never reaching higher than 65-F), well-oxygenated water to survive. Picture a gushing cold mountain stream, and you've defined ideal brook-trout habitat. The brown trout, though, prefers water in the 60-65? range, but it can tolerate much warmer water than can the brookie--up to 75-F, or, in some cases, 80-F. Brown trout can live practically anywhere that brook trout live, but brookies can't survive in many waters where brownies thrive. The two species, though, share many of the same food sources--mainly aquatic and terrestrial insects, crustaceans, and smaller fish--so if you're fishing a stream that harbors both fish, you're liable to catch either type if you are using, say, an earthworm for bait.

Compare that with the temperature preferences of the largemouth and smallmouth bass. Largemouths prefer water temperatures from 68? to 78?, but can survive in lakes and rivers that reach higher and lower temperatures. This means that the largemouth can survive, even thrive, in a large variety of waters, and it does: Largemouths are found in almost every state in the U.S., in waters ranging from huge reservoirs to slow-moving rivers to spit-across-size ponds. The smallmouth bass--a close relative of the largemouth--requires water near the 70-degree mark, and therefore is limited in range to cool rivers and large lakes and reservoirs. The range of the smallmouth is limited to the northern half of the U.S. (and some deep and therefore cool man-made waters throughout the South, where the smallmouth was stocked). There are a number of waters that hold both largemouth and smallmouth bass, but because largemouths prefer warmer water than the smallmouth, you usually won't find them inhabiting the same area.

Getting the Point
A terrestrial is a life form that lives on or in the ground (terra firma) instead of in the water. Terrestrials play a significant role in the diets of many fish. Ants, grasshoppers, crickets, mosquitoes and their larvae, grubs, mealworms, mice, and, of course, earthworms are all eaten by numerous species.

For example, one day a friend and I went fishing at a large reservoir in the Northeast for largemouth bass. We were planning to hit the coves first thing in the morning, casting to weedbeds and to the numerous felled trees that littered the shoreline. We launched the boat and started motoring to one long, narrow cove not too far away. At the entrance to the cove, a rock bluff entered the water at a steep angle, and the depth obviously dropped off quickly. There were no weeds. It wasn't an ideal place to fish for largemouths, considering that this was mid-spring and the water was still quite cool. But in our anxiousness to begin fishing, we cut the motor and cast to the bluff. Bang! A fish grabbed my lure (a jig with a white plastic trailer; see Chapter 11 for more information about lures), and a few minutes later, I brought a 2-pound smallmouth to the net. I was pleased but also surprised because I had no idea that the reservoir even contained smallmouths.

School Notes
Good fishermen check the temperature of the water they intend to fish. Although fish can detect minute differences in temperature--as little as one degree, according to some studies--most of us can't accurately gauge the temperature of water by sticking our hand in it. Water thermometers, which are sold in tackle shops, come with a long cord so temperatures can be checked at various levels.

We cast a few more times to the bluff with no results. So we fired up the motor, turned into the cove, cut power, and dropped anchor. On my second or third cast to the downed trees, a 1-pound largemouth nailed my lure--the same jig that fooled the smallmouth.

The following table lists the preferred habitats and water temperatures of popular freshwater species.

3.1. Fish Habitats and Temperature Zones


Preferred Habitat

Preferred Temperature Zone (-F)

Brook Trout

Streams, lakes, ponds


Brown Trout

Reservoirs, streams, lakes


Lake Trout

Reservoirs, lakes


Rainbow Trout

Reservoirs, streams, lakes


Largemouth Bass

Rivers, reservoirs, lakes, ponds


Smallmouth Bass

Reservoirs, lakes, rivers, streams


Spotted Bass

Streams, reservoirs



Streams, lakes, ponds



Streams, lakes, ponds


Black Crappie

Rivers, reservoirs, lakes


White Crappie

Rivers, reservoirs, lakes


Chain Pickerel

Streams, lakes



Rivers, lakes


Northern Pike

Reservoirs, lakes, rivers, streams



Reservoirs, lakes, rivers, streams


Yellow Perch

Reservoirs, lakes, rivers, ponds


Striped Bass

Rivers, reservoirs


White Bass

Reservoirs, lakes, rivers


White Perch

Reservoirs, lakes, rivers, ponds


Blue Catfish

Reservoirs, rivers, ponds


Channel Catfish

Reservoirs, lakes, rivers, ponds


Black Bullhead

Streams, lakes


Brown Bullhead

Streams, lakes, ponds


Loose Lines
A good reason to know temperature preferences of various species, and to check the temperature of the water you're fishing, is the thermocline. The thermocline is a horizontal band of water in a lake or pond that marks a rapid temperature change. If you've ever gone swimming in a lake and, upon entering a deep section, noticed that the water at your feet was much colder than the water at your belly, you felt the top layer of the thermocline. Fish will often seek out and remain in the thermocline because the water temperature they seek is within the thermocline's zone.

How Big Fish Make Little Fish
Bony fish reproduce by the female discharging eggs through her vent into the water, where a male releases milt, or semen, from his vent to fertilize them. (If you turned to this page first in hopes of finding some NC-17 material, sorry, that's it, the show's over.) Spawning, as fish reproduction is called, is an instinctive rite for fish and not much is known about the actual triggers for it, although experts in the field agree that water temperature and light have something to do with it. Some fish species will change hues and color patterns during the spawn-some turn bright, others go dark.

Various species go about spawning in slightly different ways. The brown trout and the largemouth bass, two very popular species in the United States, provide two good examples of the differences.

The brown trout spawns in the fall or the early winter, depending on the region. Brown trout in streams will deposit eggs in redds, or a shallow depression on the gravel bottom dug by the female trout with her tail. The male and female will lay side by side over the redd, depositing eggs and milt. After fertilization, the female covers the eggs in the redd with more gravel. The current holds the eggs, which number from 500 to a few thousand, depending on the size of the fish, in place in the redd. The male and female browns then leave. The eggs hatch the following spring.

Largemouth bass, however, spawn in the spring. The male (not the female, as with trout) prepares a nest-again a shallow depression-in a sandy or gravelly bottom of a lake in only two or three feet of water. The male then tries to attract a female to spawn. If successful, the male and female lay eggs and release milt over the nest. This may happen several times in one nest, with the same or a different female. The eggs hatch in a week or two, during which time the male guards the nest, defending it from all real and imagined predators, including lures cast by fishermen.

School Notes
Fish eggs are popular forage for many fish, notably rainbow trout and steelhead (which are ocean or Great Lakes rainbows that spawn in rivers). A popular bait for both fish are salmon eggs, which are sold in jars. One pea-sized egg is usually impaled on a similar-sized gold-colored hook. Often the pale yellow salmon eggs are dyed in bright colors (usually orange) and/or scented for extra fish appeal.

Although the reproductive habits of the brown trout and the largemouth bass differ, both species-as well as hundreds of other species--are very successful spawners in the U.S., enough so that natural propagation keeps thousands of waters filled with fish.

Loose Lines
Because bass are very vulnerable to fishermen when they are spawning, some states don't open the bass fishing season until after the spawn is complete. On very heavily fished lakes, it would be possible to decimate the bass population if fishermen caught and kept all those males guarding the nest.

Do Fish Feel Pain?
This is a question commonly asked by those new to fishing. And it's a good question, too; many otherwise experienced anglers don't know the answer. Actually, it's difficult to prove scientifically whether a fish feels the sting of a hook in its mouth the same way that I would feel that same hook in my mouth (that has never happened to me, although a friend of mine once hooked himself in the nose while flyfishing on a very windy day, and he said it hurt quite a bit).

We do know that fish respond to being hooked: They fight and leap and pull toward the bottom, always putting pressure against the angler's fishing line (never in my life have I hooked a fish that came directly to my hand or net). But that still does not signify pain as we know it. As a matter of fact, fish exhibit some traits from which we can construe that they don't feel pain at all.

For instance, many times I have had a fish on my line--including bass, pickerel, bluegills, and numerous saltwater species--that I lost moments after I hooked it. These fish had the point of the hook embedded far enough into their mouths to respond to it by fighting. For whatever reason--I didn't set the hook hard enough, the hook point itself was dull, I didn't keep a tight enough line--the fish was able to dislodge the hook from its mouth ("throwing" or "spitting" the hook, as it is commonly referred to). Yet on one of my next few casts, I would hook the very same fish.

When I was young, sometimes I would lie down on a small boat dock and fish for the little bluegills and pumpkinseeds that took refuge in the shade of the structure. I would dangle a worm-baited hook just a foot or so under the surface and watch the panfish come out from the shade, observing the worm. Eventually one of them would dart over and try to grab the worm--try, because often the mouths on those diminutive bluegills would be too small to engulf the whole worm. So it would become a matter of striking exactly when just the point of the hook was positioned at, or just inside of, the fish's mouth. So many times I would have a bluegill on the hook for a matter of seconds, watching while it tugged against the line and tried to swim back to the safety of the dock's shadow, and then it would throw the hook. I'd reel in, rebait with a fresh worm, drop it back in the same place, and witness that same bluegill come out, study the worm, and try to eat it again.

School Notes
If I catch a fish that I intend to keep, and don't have the means to keep it alive until I clean it or fillet it, I kill it. Besides putting the fish out of its misery, it ensures good-quality meat. Fish that jump around until they expire may acquire an off-taste.

Similarly, I have fished lakes for bass with a topwater lure (which imitates a frog or a mouse or a wounded baitfish) and had a bass jump up, grab the lure, and start swimming away. Now, many surface lures are made of hard plastic and feel very much unlike a frog, not to mention the shiny and sharply honed hooks dangling from them. The bass would shake its head, losing the hook, and then come back to hit it again.

Also, many people have witnessed sharks in a "feeding frenzy" that are so keyed into eating that one shark will occasionally take a bite out of another. That wounded shark would then--as gruesome as it may sound--turn and actually begin feeding on itself.

Some people may argue that fish dofeel pain; the reason that they don't react to it is that their sense of hunger--the predatory instinct--is much stronger than their sense of pain. But I've also fished enough times when, for whatever reason, the fish just won't eat anything, to disallow that reasoning. My personal, unscientific theory is that fish do feel something when they're hooked, but it is not at all the same sensation that humans would experience. In other words, it doesn't hurt them.

Loose Lines
Sometimes a fish gets away from the angler by breaking the line, with the hook still embedded in its jaw. Surprisingly, many fish survive such an event, because the hook will rust and fall away. I have even caught fish with an old fishhook still attached to them, and they didn't show any outward signs of being affected by it (obviously they were still well enough to eat). Fish that swallow the hook are a different case, and there have been numerous--and conflicting--studies on whether or not the majority of such fish survive. The type and size of the hook, where in the fish it is located, the species of the fish, and the water it is in are all factors.

Pollution and How Fish Deal with It
I used to live near a picture-perfect trout stream in rural Pennsylvania that had signs posted on trees along its banks notifying anglers that the water was polluted. Chemicals had leached from some old barrels that had been buried near the stream some time ago, and tests had shown that the fish carried the chemicals in their bodies. The state fish commission no longer stocked the stream. That was OK, because it was brimming with brown trout that had "held over" from previous stockings years ago. My friends and I caught and released hundreds of trout from that stream over the course of a couple of years, and they were beautiful, sparkling fish. One day there I caught a brown trout that was no more than five inches long--proof that the trout were successfully reproducing.

At one time I also lived close to a river that had one color year-round: brown. Street sewers drained into it and various manufacturing companies released who-knows-what from discharge pipes along its length. Occasionally the river would emit a distinct and very unpleasant odor. Its shores were lined with garbage and waste. Yet the river held fish--a healthy population of carp and a few species of panfish.

Cautious Casts
Many of the harmful chemicals found in fish that live in polluted waters collect mainly in the organs, which are not normally consumed, and the skin. If you know or suspect that the water is polluted, remove skin before cooking.

Many fish species are hardy and can withstand pollution to an amazing extent. The problem with fishing in polluted waters--besides the obvious loss of aesthetic value--is that the fish might be dangerous to eat, because of the build-up of chemicals inside their bodies

Loose Lines
The carp is an extremely hardy and prolific species of fish that is native to Europe, where it is highly regarded as a gamefish. In the U.S., however, where the species was introduced into a number of waters in the late 1800s, carp are disdained by many fishermen. This is because carp are considered ugly by those who pursue trout, bass, and other "glamour" species; they muddy waters because of their widely wandering bottom-feeding habits; and possibly because they can survive where no other fish species can, such as highly polluted lakes and rivers. Yet carp grow to tremendous sizes, exceeding 40 pounds in many waters. They are also edible (when skinned and the dark meat removed), and are an ingredient in gefilte fish. Smoked carp is also considered delicious.

Fortunately, U.S. waters are less polluted now than they were just two decades ago, thanks to rigid enforcement of environmental regulations. Also, state fish and game departments keep close track of the degree of pollution in fishable waters, and institute dietary guidelines for people who intend to keep and eat their catch. There are many different types of pollutants present in our waters, but basically there are two types of guidelines issued if necessary: Either no fish should be consumed, or no fish should be consumed by children under a certain age or by pregnant women. Contact your state fish and game department for details about specific waters, species affected, and guidelines.

Fair Use Notice and Disclaimer
Send questions or comments about this web site to Ann Berlin,