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.
Mating System: monogamous ; polyandrous
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).
Breeding interval: 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 (male): 2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous
Average age at sexual or reproductive maturity (male)
Sex: male: 730 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 730 days.