Brook Trout (Salvelinus fontinalis)

Brook trout are technically not true trout but are closely related to trout; they are charr and members of a family composed of lake trout, bull trout, bluebacked trout, Dolly Varden, and arctic charr. As a native North American fish, and a sensitive one that has been displaced in some habitats as the result of fish stocking or water degradation, the brook trout has long been a favorite of stream and pond anglers, especially in the northeastern region of North America.

Identification

Brook trout have a coloration and patterns so unique that there is seldom any confusion with other fish, especially when one is looking at a native specimen (which will be richer and more brightly marked and colored than a hatchery specimen). Three external features allow immediate separation of the brook trout from either the brown or the rainbow trout or other charr. White pipings on the outer edges of all but the caudal (tail) fin identify it as a charr.

On the interior of the white leading edges on the fins is a narrow black stripe. Body spots of a true trout are on a light background but are reversed in all charr. Trout have large scales easily seen by the eye, whereas charr have very small scales. The feature that is wholly unique to the brook trout is the wormlike wavy lines, called vermiculations, on the back and the head. These appear on the dorsal, the adipose, and the caudal fins like a series of tiger stripes.


Like all salmonids, the brook trout sports a vestigial adipose fin on its back. It also has paired pectoral and pelvic fins and a singular anal fin, just posterior of the vent.

Coloration can vary greatly, depending on the environment, ranging from a light, metallic blue in fish that enter saltwater (which are called salters) or in fish that leave natal streams and spend part of the year in large, deep, clear lakes (which are called coasters), to dark brown and yellowish bodies in trout trapped behind beaver dams or in high mountain ponds. In both sexes, body colors intensify during spawning and are more pronounced in males.

Size/Age

Brook trout are not a long-lived fish, generally surviving into their fourth or fifth year, although some fish have lived to at least 10 years of age. In most environs, the average brook trout caught is between 7 and 10 inches long and weighs considerably less than a pound. In many of their small-water natural habitats, the conditions do not exist to foster large sizes.

A brook trout exceeding 12 inches in most northeastern waters is a sizable fish, and one exceeding 2 pounds is uncommon. Nevertheless, brook trout are capable of reaching larger sizes; a 14-pound, 8-ounce brook trout caught in 1916 is the all-tackle world record for the species, and that individual measured 31 inches in length.

Life history/Behavior

Brook trout spawn in the late fall and the early winter. Immature and small, adult brook trout are likely to stay in a stream even when access to a lake or a pond is nearby because stream habitats offer more protection from predators. During summer months, larger brook trout typically inhabit the lake, which has larger food items, and move to rivers or streams only to spawn.

Some populations of brook trout migrate to sea for short periods. They move downstream and upstream in the spring or the early summer and remain in estuaries and ocean areas where food is plentiful. After roughly 2 months, they return to freshwater. Not all fish in a population migrate, nor do they necessarily do so every year. Sea-run brook trout live longer and grow larger than strictly freshwater brook trout.

Food and feeding habits

Brook trout from 4 to 8 inches long feed mainly on aquatic and terrestrial insects. Between 8 and 12 inches, they begin feeding on small fish. Large trout, particularly in northern waters during the summer, are known to eat small mammals (mice, voles, shrews, and lemmings) that find their way into the water.

Other Names

Eastern brook trout, speckled trout, native, spotted trout, speckled charr, brook charr, salter, coaster, squaretail, brookie, aurora trout, mountain trout; French: truite mouchetée.

Distribution

Brook trout populations still exist over much of the species’ original distribution. Their range covers all of the northeastern United States, the Canadian Maritimes, Labrador, and Newfoundland, and they exist in all the Quebec and Ontario rivers and streams that enter Hudson and James Bays.

The 96° longitudinal line, where it crosses into Minnesota, is the natural western limit of brook trout in the United States, although they have been introduced elsewhere and as far west as California. The most southerly brook trout distribution is the headwaters of the Chattahoochee River in Georgia.

Habitat

Compared to all other charr, as well as to salmon and trout, brook trout are the least specialized in their habitat demands. This allows them to live in a great variety of environments, with a wide range of tolerances. They inhabit small trickles, rivulets, creeks, and beaver ponds. They live in larger streams and any lake, from the Great Lakes to little lakes and ponds, to small rivers and big rivers with tumbling falls and rapids.

Because of a unique organ (the glomerulus) in their kidneys, they are anadromous and can move into riverine estuaries and are at home in brackish streams that feel the surge of tides, in a purely saline bay, or even the oceans themselves. They are, however, the classic example of a coldwater species and thrive best in the northern half of the Northern Hemisphere.

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