FWS Focus

Overview

Characteristics
Overview

The brook trout are members of the char family. They prefer small spring fed streams and ponds with sand or gravel bottom and vegetation. They spawn over gravel in either streams or lakes, with ground water percolation or in the spring fed areas in lakes. Young brook trout feed on plankton and progress to insects until they are adults.

Scientific Name

Salvelinus fontinalis
Common Name
brook trout
charr
salter
sea trout
coaster brook trout
aurora trout
FWS Category
Fishes
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Life Cycle

Characteristics
Reproduction

Brook trout spawn in late summer or autumn depending on the latitude and temperature (Scott and Crossman, 1985). The type of area required for brook trout spawning is one that offers loose, clean gravel in shallow riffles or shoreline area with an excellent supply of upwelling, oxygen-rich water (LaConte, 1997). Mature fish have been known to travel many miles upstream to reach adequate spawning grounds (Scott and Crossman, 1985). Females are able to detect upwelling springs or other areas of ground-water flow, which make for excellent spawning grounds. Brook trout reach maturity on an average at the age of two and spawn every year, although their size at first maturity depends on growth rate and the productivity of thier habitat (Everhart, 1961). Males often outnumber females at the spawning site, but only rarely is more than one male able to fertilize the eggs in a particular redd (Scott and Crossman, 1985; Blanchfield et al., 2003). The females clear away debris and silt with rapid fanning of her caudal fin while on her side, creating a redd (Scott and Crossman, 1985). The redd is where the eggs will be deposited and fertilized after the males compete for spawning right to the female (Scott and Crossman, 1985). The redd actually resembles a pit that is 4-12 inches in depth (Everhart, 1961). To gain the spawning right of the female the males compete for position by nipping and displaying themselves to the competitor males (Mills, 1971). When spawning is actually taking place the male takes a position to hold the female against the bottom of the redd and both of the fish vibrate intensely while eggs and milt are simultaneously discharged (Scott and Crossman, 1985). Very shortly after this exchange takes place the female works to cover the fertilized eggs with gravel by digging slightly upstream and letting the current carry the gravel down to fill the redd (Everhart, 1961). The eggs are initially adhesive to prevent them from washing away so they are able to incubate within the gravel (Scott and Crossman, 1985). The total time of incubation depends on factors such as temperature and oxygen (Scott and Crossman, 1985). After hatch the fry remain in the gravel until the yolk sac is absorbed then the fry swim up out of the gravel to begin the next stage of their life (Scott and Crossman, 1985). (Blanchfield, et al., 2003Everhart, 1961LaConte, 1997Mills, 1971Scott and Crossman, 1985)

Characteristic category

Behavior

Characteristics
Behavior

Behavior varies greatly in brook trout depending on their habitat; for example, some populations in streams draining into marine environments have individuals that take to living in the marine environment, only returning to the river in order to spawn (Mills, 1971). Brook trout that take to the sea are called sea-run trout, salters, or coasters and are considered anadromous, similar to salmon (Mills, 1971).

While coasters migrate extensive distances to spawn, freshwater populations of brook trout travel comparatively shorter distances upstream (Mills, 1971). The brook trout is one of the least tolerant of competing species of coldwater fishes, it does best in waters where there are no fishes competing for similar niches (Everhart, 1961).

There is a relatively high amount of territorial behavior found in brook trout and territory is established shortly after emergence from the redd (Latta, 1968). These territories are established as a result of aggressive behavior (Latta, 1968). Their aggressiveness is shown to increase when factors such as current velocities, availability of food, and the degree of visual isolation heighten (Latta, 1968).

The growth rate of brook trout vary depending on their habitat; for example, an individual in a cold spring brook will reach no more than 15.24 cm after four years (Mills, 1971). An individual that inhabits a relatively rich lake habitat may be 38.1-50.8 cm in length and reach weights of around 1.8 kg in the same amount of time (Mills, 1971). The largest brook trout ever caught was a 6.57 kg. individual taken on the Nipigon River in Rabbit Rapids, Ontario (Scott and Crossman, 1985). Brook trout seldom live over 5 years and virtually never beyond 8 years (Scott and Crossman, 1985). The population size of brook trout populations is primarily determined by disease, predation or starvation during the first year of life (Mills, 1971). Brook trout are very specific when it comes to habitat, they require cold, clean, well-oxygenated water and even a seemingly minor change in these conditions can result in the loss of brook trout populations (LaConte, 1997). (Everhart, 1961LaConte, 1997Latta, 1969Mills, 1971Scott and Crossman, 1985)

Characteristic category

Physical Characteristics

Characteristics
Size & Shape

The brook trout's body is elongate with an average length of 38.1-50.8 cm, is only slightly laterally compressed; the body has its greatest depth at or in front of the origin of the dorsal fin (Scott and Crossman, 1985). Another physical characteristic of the brook trout is an adipose fin and a caudal fin that is slightly forked (Hubbs and Lagler, 1949). The brook trout also has a large terminal mouth with breeding males developing a hook or kype on the front of the lower jaw (Scott and Crossman, 1985).

Weight

In streams, brook trout can weigh 1 to 5 pounds. 

Color & Pattern

The coloration of the brook trout is very distinct and can be spectacular. The back of the brook trout is dark olive-green to dark brown, sometimes almost black, the sides are lighter and become silvery white ventrally (Scott and Crossman, 1985). On the back and top of the head there are wormy cream colored wavy lines known as vermiculations which break up into spots on the side (Scott and Crossman, 1985). In addition to the pale spots on the side there are smaller more discrete red spots with bluish halos (Scott and Crossman 1985). The fins of the brook trout are also distinct; the dorsal fin has heavy black wavy lines, the caudal fin has black lines, the anal, pelvic and pectoral fins have white edges followed by black and then reddish coloration (Scott and Crossman, 1985). (Scott and Crossman, 1985Hubbs and Lagler, 1949)

Characteristic category

Habitat

Characteristics
Habitat

Brook trout can be found in three types of aquatic environments with very specific habitat requirements in each: rivers, lakes, and marine areas. Freshwater populations occur in clear, cool, well-oxygenated streams and lakes with water temperatures that remain below 18.8 C and where there is little to no siltation. Stream dwelling brook trout require habitat that consists of resting areas in pools, feeding sites near riffles or swiftly flowing water, and escape cover that is normally found along undercut banks, under woody debris, trees or large rock ledges. Brook trout that reside in marine environments migrate there from freshwater tributaries and tend to stay close to river mouths.

Lake

A considerable inland body of standing water.

Coastal

The land near a shore.

Marine

Of or relating to the sea.

Lake
Mountain
Coastal
River or Stream

A natural body of running water.

Characteristic category

Food

Characteristics
Food

The food habits of brook trout vary according to their age and life history stage. A brook trout will virtually eat anything its mouth will accommodate, including mostly many aquatic insect larvae such as caddisflies, mayflies, midges, and black flies. Other organisms consumed include worms, leeches, crustaceans, terrestrial insects, spiders, mollusks, a number of other fish species, frogs, salamanders, snakes and even small mammals like voles should they find one in the water. As brook trout become larger their diet shifts more towards a piscivorous one. 

Geography

Characteristics
Range

Brook trout are native to much of northeastern North America. To the north, brook trout can be found in most of eastern Canada from Newfoundland to the western side of Hudson Bay. To the south, brook trout are native to the Great Lakes Basin and in headwater tributaries of the upper Mississippi River basin of Minnesota, Wisconsin, and northeastern Iowa. in the northeastern United States, brook trout are native to all Atlantic coastal drainages southward to Virginia. In the southern Appalachian Mountains, brook trout are native to higher-elevation streams draining both to the Atlantic Ocean and the headwaters of the Tennessee River drainage, with the southernmost range being in the headwaters of the Chattahoochee River in northern Georgia.

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