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Aurora trout

Salvelinus fontinalis

What do they look like?

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). Brook trout have 10-14 principle dorsal rays, 9-13 principle anal rays, 8-10 pelvic rays, and 11-14 pectoral rays (Scott and Crossman, 1985). 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).

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, 1985; Hubbs and Lagler, 1949)

  • Range mass
    1 to 6 kg
    2.20 to 13.22 lb
  • Range length
    38.1 to 50.8 cm
    15.00 to 20.00 in

Where do they live?

Brook trout are found as far south as Georgia in the Appalachian mountain range and extend north all the way to Hudson Bay. From the east coast their native range extends westward to eastern Manitoba and the Great Lakes (Willers, 1991). The fish has been introduced, very successfully in some areas, into many parts of the world including western North America, South America, New Zealand, Asia, and many parts of Europe (Scott and Crossman, 1973). (Willlers, 1991; Scott and Crossman, 1985; Willlers, 1991)

What kind of habitat do they need?

Brook trout are found in three types of aquatic environments: rivers, lakes, and marine areas. Their living requirements in these environments are very specific. The freshwater populations occur in clear, cool, well-oxygenated streams and lakes (Scott and Crossman, 1985). Brook trout thrive in these environments with temperatures that remain below 18.8 C and where there is little to no siltation (LaConte, 1997). Stream dwelling brook trout require three habitat components, which include resting areas in pools, feeding sites near riffles or swiftly flowing water, and escape cover which normally is found along undercut banks, under woody debris, trees or large rock ledges ("Brook Trout," 1987). Brook trout that reside in marine environments migrate there from freshwater tributaries and tend to stay close to river mouths. ("Brook Trout", 1987; Scott and Crossman, 1985; LaConte, 1997)

How do they reproduce?

Usually only a single male is able to fertilize the eggs that a female lays in a redd, but occasionally more than one male is able to do so. Usually the largest males are the most successful breeders. (Blanchfield, et al., 2003)

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., 2003; Everhart, 1961; LaConte, 1997; Mills, 1971; Scott and Crossman, 1985)

  • How often does reproduction occur?
    Brook trout breed once per year
  • Breeding season
    Spawning occurs in late summer or autumn
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    730 days
  • Average age at sexual or reproductive maturity (male)
    2 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    730 days

How long do they live?

How do they behave?

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, 1961; LaConte, 1997; Latta, 1969; Mills, 1971; Scott and Crossman, 1985)

How do they communicate with each other?

What do they eat?

The food habits of brook trout vary according to their age and life history stage. As fry, or very young fish, brook trout feed primarily on immature stages of aquatic insects (Everhart, 1961). In general a brook trout's diet can be likened to a smorgasbord of organisms with prey ranging from mayflies to salamanders (Wittman, 2001). 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 (cannibalism is limited to spawning time and spring), frogs, salamanders, snakes and even small mammals like voles (e.g. Microtus, Cleithrionomys), should they find one in the water (Scott and Crossman, 1985). As brook trout become larger their diet shifts more towards a piscovourus one (Everhart, 1961). Sea-run brook trout eat fish and intertebrates that are commonly found in marine environments (Scott and Crossman, 1985). (Everhart, 1961; Scott and Crossman, 1985; Wittman, 2001)

  • Animal Foods
  • mammals
  • amphibians
  • reptiles
  • fish
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans

How do they interact with us?

As a gamefish the brook trout is very highly sought after and one of the most popular, especially in north eastern North America (Scott and Crossman, 1985). The brook trout can be caught by fishing with artificial flies, spin casting, or with live bait (Scott and Crossman, 1985). Brook trout and their vastly popular sport fishing bring to a community related recreational activities such as camping, boating, and the need for gear, guides and transportation, all of which provide positive economic opportunities (Hubbs and Lagler, 1949). Brook trout have been raised in hatcheries and distributed world wide in hope of creating the above mentioned opportunities in places where they do not natively occur or to reestablish and strengthen native populations (Scott and Crossman, 1985). (Hubbs and Lagler, 1949; Scott and Crossman, 1985)

Are they endangered?

There are many extensive conservation efforts directed towards brook trout, especially naturally reproducing brook trout populations. This is because in many northeastern states and Canada brook trout, the only native stream dwelling trout in many of these places, are very susceptible to urbanization and deforestation and its effects on the surrounding aquatic ecosystems. Ohio for example has only two naturally reproducing populations of brook trout left and breeds these populations in hatcheries then placing them in other suitable habitats to reestablish these populations (LaConte, 1997). Many other states and areas in Canada are performing similar projects to preserve this treasured and threatened natural resource. (LaConte, 1997)

Some more information...

When in breeding colors the male brook trout are considered by many to be one of the most colorful and beautiful of all freshwater fishes (LaConte, 1997). Another interesting fact is that brook trout are actually a char not a trout (LaConte, 1997). The brook trout has also been hybridized with the brown trout, by combining brown trout (Salmo trutta) eggs with brook trout sperm, to produce a sterile tiger or zebra trout, which has proven itself to be a very good gamefish (Mills, 1971). The brook trout's sperm has also been combined with the eggs of a lake trout (Salvelinus namaycush) which results in a splake, a fish that has been introduced into some of the North American Great Lakes (Mills, 1971). (LaConte, 1997; Mills, 1971)


William Fink (editor), University of Michigan-Ann Arbor.

James Roberts (author), University of Michigan-Ann Arbor.


1987. Brook Trout. J Mayhew, ed. Iowa Fish and Fishing. Des Moines, Iowa, USA: Iowa Department of Natural Resources. Accessed November 04, 2004 at

Blanchfield, P., M. Ridgway, C. Wilson. 2003. Breeding success of male brook trout (Salvelinus fontinalis) in the wild. Molecular Ecology, 12(9): 2417-2428.

Everhart, W. 1961. Fishes of Maine. Augusta, Maine, USA: The Maine Department of Inland Fisheries and Game.

Hubbs, C., K. Lagler. 1949. Fishes of the Great Lakes Region. Ann Arbor, Michigan: University of Michigan Press.

LaConte, V. 1997. Ohio's Native Brook Trout. Wild Ohio, Fall.

Latta, W. 1969. Some factors affecting survival of young-of-the-year brook trout, *Salvelinus fontinalis* (Mitchill), in streams. Pp. 229-239 in T Northcote, ed. Symposium on Salmon and Trout in Streams. The University of British Columbia:

Mills, D. 1971. Salmon and Trout: A resource, its ecology, and management. Bungay, Suffolk, Great Britain: The Chaucer Press.

Scott, W., E. Crossman. 1985. Freshwater Fishes of Canada. Ottawa, Canada: Minister of Supply and Services Canada.

Willlers, B. 1991. Trout Biology. New York City, New York: Lyons and Burford.

Wittman, S. 2001. "Brook Trout" (On-line). Fish of the Great Lakes. Accessed 11/05/04 at

University of Michigan Museum of ZoologyNational Science Foundation

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Roberts, J. 2000. "Salvelinus fontinalis" (On-line), Animal Diversity Web. Accessed May 22, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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