Categories: fishing

Trout salmon basics

trout salmon basics

Trout and salmon have long been considered superior gamefish, the ultimate in wariness and fighting ability. In years past, many anglers regarded them as the only true gamefish.

Unfortunately, this wary nature has led to the popular notion that the fish are intelligent, and therefore difficult for the average angler to catch. However, there is no evidence to indicate they are more intelligent than other gamefish species.

The notion of intelligence is reinforced when anglers see feeding trout being “put down” by even the slightest movement or vibration. However, this is an instinctive reaction, and should not be confused with intelligence. Like any other fish, trout flee for cover to avoid predators. As soon as they hatch, trout face attacks from predatory insects, crayfish, and other small fish. As they grow older, trout are attacked by larger fish and by kingfishers, herons, and other predatory birds. A trout’s wariness is also the result of natural selection; those that lack sufficient wariness do not live to reproduce.

Their preference for cold water distinguishes trout and salmon from other gamefish. Although temperature preferences vary among trout and salmon species, most seek water temperatures from 50 to 65°F (10 to 18°C), and avoid temperatures above 70°F (21°C). This requirement means they can live only in streams or lakes fed by cold water sources such as springs or snowmelt, or in lakes with deep, unpolluted water.

Trout and salmon belong to the family Salmonidae. Besides trout and salmon, the family includes grayling, found mainly in Alaska, the Yukon, and the Northwest Territories; and whitefish, which are widely distributed in the northern states and Canada but have minor importance to anglers.

For the purposes of this article, the term “trout” includes not only true trout (genus Oncorhynchus and Salmo) but also chars (genus Salvelinus). True trout, such as browns and rainbows, have dark spots on a light background; chars, such as brook trout and Dolly Varden, have light spots on a dark background. Chars require colder water than true trout.

Identifying Salmonid Groups

dark spots on light background trout and atlantic salmon

Atlantic salmon are closely related to brown trout and belong to the same genus, Salmo. Pacific salmon belong to a different genus, Oncorhynchus, meaning “hooknose,” and are related to rainbow trout. Pacific salmon spawn only once, dying soon afterwards; other members of the family may live to spawn several times. All salmon species are anadromous; they spend their lives at sea and then return to freshwater streams to spawn. Salmon stocked in freshwater lakes spawn in lake tributaries.

Many species of trout, including rainbow, brook, brown, and cutthroat, have anadromous forms with a different appearance than the forms limited to freshwater. The anadromous forms are generally sleeker and more silvery.

Powerful fighters, trout and salmon have remarkable stamina. Some species, like rainbow trout and Atlantic salmon, leap repeatedly when hooked; others, like brook

trout, wage a deep, bulldog-style battle. Most trout and salmon are excellent eating, but there is a strong trend toward catch-and-release fishing. In some heavily fished water, catch-and-release is mandatory. This has long been the accepted practice for Atlantic salmon because the species is so rare and so treasured as a gamefish. Catch-and-release fishing ensures that the fish remain in a stream long enough to spawn and produce “wild” progeny. The other alternative, frowned upon by most trout enthusiasts, is put-and-take stocking of hatchery-reared trout.

To become a successful trout or salmon angler, you must shed the notion that there is an aura of mystery surrounding these fish. Although they live in prettier settings than most other fish, they have the same behavior patterns and the same needs for food and cover. Learn to think of their basic needs and you will have no trouble finding them. Learn to approach them stealthily, like a predator, and you will have no trouble catching them.


Stream fishermen know that a sudden movement, a heavy footstep, a shadow, or a fly rod glinting in sunlight will send a trout scurrying for cover. Salmonids depend mainly on vision to detect danger, but they also have an excellent sense of smell and a well-developed lateral-line sense.

VISION. When approaching salmonids, remember that they can view the outside world clearly through a “window,” a circular area on the surface of the water whose size depends on the depth of the fish. The diameter is slightly more than twice as wide as the fish is deep. A trout at a depth of 2 feet (61 cm) would have a window 4 feet, 6 inches (137 cm) wide. Surrounding the window, the surface is a mirror, so the fish can’t see out.

Many frustrated fishermen can attest that salmonids have excellent color vision. An olive nymph may produce fish after fish, but a similar nymph in a slightly darker green will not draw a strike. Because the fish are so color selective, experienced anglers often carry similar fly or lure patterns in several different colors or shades in an attempt to determine the color of the day.

Trout and salmon have only fair night vision. With the exception of large brown trout, they do little feeding after dark. Even browns seem to have difficulty locating a fly unless it produces noise or vibration.

SMELL. Trout and salmon use their sense of smell to find food, avoid predators, and locate spawning areas. If you drop a gob of fresh salmon eggs in a clear pond filled with rainbows, the eggs will “milk” as they sink, leaving a scent trail. Feeding trout mill about until they cross the trail, then they turn and follow it to the eggs.

Researchers in British Columbia found that salmon turned back from their spawning run and headed downstream when a bear was fishing upstream of them. The salmon detected a chemical emitted by the bear called L-serine. This chemical is also given off by human skin.

Salmon and migratory forms of trout navigate at sea or in large lakes by using the sun, currents, and the earth’s magnetic field. These clues enable them to return to the vicinity of their home stream at spawning time. Once they get that far, they rely on scent to find just the right stream. Amazingly, they can return to the exact area of the stream where their lives began. When researchers cut a salmon’s olfactory nerves, it could not find its way back.

Biologists have discovered that they can dramatically increase the percentage of chinook salmon returning to a given stream by “imprinting” the young fish before they move to open water. Just as the young start to smolt, a chemical that can be detected in extremely low concentrations is dripped into the stream. The smell of this chemical is somehow locked into the fish’s memory. Then, when the salmon reach maturity, the same chemical is again dripped into the stream. In some cases, this technique has doubled the return rate.

LATERAL LINE. Veteran stream fishermen step very lightly when wading the streambed or walking the bank, even when outside the fish’s field of vision. They also realize that vibration-producing lures work better in murky water or after dark than lures that produce little vibration. The fish evidently detect footsteps and lure vibrations with their lateral-line system, a network of ultra-sensitive nerve endings along the side of the body.


During their early years, trout and salmon feed mainly on immature forms of aquatic insects, and to a lesser extent on adult insects, both aquatic and terrestrial. They also eat small crustaceans, mollusks, and earthworms. As they grow larger, they continue to eat large numbers of insects, but small fish make up an increasing percentage of their diet. Large trout do not hesitate to eat small animals like frogs and mice. Some salmon species, such as sockeye and pink, are plankton feeders, filtering tiny organisms from the water with their closely spaced gill rakers. This feeding behavior makes them very difficult to catch on hook and line. Practically all trout and salmon will eat the eggs and young of other species, and of their own kind, when the opportunity presents itself.

How fast a trout grows depends not only on the type of food it eats, but also on the fertility and size of the stream.

Generally, trout that feed primarily on insects grow more slowly than those that eat small fish; insect feeding uses more energy for nutrients obtained. Trout in mountain streams usually grow more slowly than trout in farm-country streams. The high

altitude streams are colder and less fertile, so they produce considerably less food. Brown trout, for instance, seldom exceed 1 pound (0.45 kg) in small mountain streams where insects are the major food. In contrast, they grow to 15 pounds (7.4 kg) or more in rivers with marginal temperatures for trout but with plenty of baitfish.

Trout that live in small brooks have a slower growth rate than those in good-sized rivers because the bigger water offers a greater abundance and diversity of foods. The size of the spawning stream also seems to affect the size of chinook salmon, even though the salmon do very little feeding in the stream. Studies have revealed that the larger the spawning stream, the larger the salmon.

Genetics also influence growth rate. Fast-growing strains of many species have evolved naturally or have been produced by fish culturists who select and breed the fastest-growing individuals from each year-class. Donaldson rainbow trout, a strain selectively bred for fast growth at the University of Washington, may reach 10 pounds (4.5 kg) in only two years, provided they have enough food. A normal rainbow of the same age weighs less than a pound (0.45 kg), even if food is abundant.

Male trout and salmon grow faster than females; salmonids differ in this respect from most other fish species.

Salmon diet and lifespan

The next article talks about the common stream insects like the mayfly, stonefly, caddisflies and more which is essential to the fly fishing enthusiast who wants to learn more about the insects and tying flies that closely mimic the thing.



Robert Frost

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