Shared Characteristics—What Makes A Fish A Fish?

Scales—Most fish have distinctive scales, although some, like catfish, have more of a skin. Fish typically have a slime coat of some sort to help stave off infections. While most coatings are inoffensive, some are slimy and rather strongly scented!

Coloration—Fish display an amazing range of colors and distinctive patterns, although there are some universal principles. Species that suspend in open water are usually silvery, white or light in color, with sunlight reflecting off their bodies helping them to blend in to the coverless environment. Those that chiefly live in and around cover are often mottled with dark colors, functioning as a camouflage to protect them from larger predators and to disguise them from smaller prey. When they switch from one area to another, they tend to adjust the intensity of their coloration, turning lighter or darker. They’re not chameleons, but they do adapt.

Fish also tend to be dark in color along their backs, and light or white along their bellies, with a transition between. This is the principle of countershading: Sunlight shining down on their backs brightens the upper portion of their bodies, while their shaded underbelly blends in with the colors above, rendering them less visible to predators.

Males versus Females—Ah, the battle of the sexes, even in fish! Not really, but you will find that the females of most freshwater species grow to a larger average size than males. Differences between the sexes are most apparent near spawning time, although during the rest of the year, larger fish (mostly females) may tend to school together and feed on a certain forage type or size, while smaller fish (mostly males) may school in other locales and feed on smaller food items.

Spawning/reproduction—Female freshwater fish lay eggs, with the eggs being fertilized by males in close attendance. Eggs tend to develop more rapidly (perhaps a few weeks) in warmer temperatures, and more slowly in colder water (possibly months). Most freshwater gamefish spawn in the spring, although salmon, char and some trout spawn in fall. Water temperature is a key trigger to the timing, although other factors like sunlight penetration into the water are likely involved.

Where and fish lay eggs, however, is highly dependent on the species. Some deposit eggs on rocks, other atop weeds or flooded brush. Nesting fish like those of the sunfish family (bass, panfish) sweep out pit-type nests to spawn in, with males remaining on the nest for several weeks to protect the eggs and newly-hatched fry from predators. Broadcast spawners like walleyes simply dump their eggs into rocks swept by current, and then leave the area unguarded. Trout and salmon, meanwhile, create crude nests in rocky current areas, but don’t guard them after spawning. To each its own.

Schooling behavior—Most fish are not loners; instead, they often school together in groups, large or small, to help defend them from predators (safety in numbers), or to increase their feeding effectiveness. They display a social lifestyle not because they’re friendly, but to enhance efficiency and survival. The result is, you’re often trying to locate schools of fish rather than individuals, and when you locate and convince one into biting, chances are there are more nearby. Fish that suspend and roam in open water tend to form the largest schools, while those that function in shallow cover tend to function in smaller groups, all else being equal.

Pea brain—They may say that you need to think like a fish in order to catch a fish, but you can put that saying out of your mind. Fish have small brains and aren’t about to outthink your best efforts. Instead, they tend to react by instinct, which is what you must appeal to most. You’d never get an entire roomful of smart people to agree on anything, but when a weather change suddenly affects the entire fish population and they go off-bite, well, that’s an instinctual reaction to an outside stimulus.

That’s not to say that fish can’t learn, however. Studies in the lab and fishing on the water show that fish can and do learn to avoid certain negative stimuli, and to experience positive reinforcement when feeding successfully. Fish can eventually become conditioned to certain lures or presentations, reducing their effectivness. This partially explains why a hot new lure can be so hot at first; either the fish haven’t yet learned to avoid it, or the ones most likely to respond to it haven’t yet been caught and released, recaught, or kept. Thus the constant urge for fishermen to experiment and discover a new wrinkle to provide an advantage over their fellow anglers—and the fish.