Brook trout
The brook trout is a species of freshwater fish in the char genus Salvelinus of the salmon family Salmonidae native to Eastern North America in the United States and Canada. Two ecological forms of brook trout have been recognized by the US Forest Service. One ecological form is long-lived potamodromous populations in Lake Superior known as coaster trout or coasters. The second ecological form is the short-living predaceous anadromous populations which are found in northern lakes and coastal rivers from Long Island to Hudson Bay, which are referred to as salters. In parts of its range, it is also known as the eastern brook trout, speckled trout, brook char, squaretail, brookie, or mud trout, among others. Adult coaster brook trout are capable of reaching sizes over 2 feet in length and weigh up to 6.8 kg, whereas adult salters average between 6 and 15 inches in length and weigh between 0.5 and 2.3 kg. The brook trout is characterized by its distinctive olive-green body with yellow and blue-rimmed red spots, white and black edged orange fins, and dorsal vermiculation. The diet of the brook trout is restrictive to the season and location of the fish, but will typically consist of terrestrial and aquatic insects, fry, crustaceans, zooplankton, and worms.
Throughout history, non-native brook trout have been transplanted beyond its native borders, where it has spread across North America and much of the world. These brook trout have been introduced since the 1800s by means of artificial propagation and aquaculture in hope of promoting fishery resources. Through this transplantation, brook trout have been observed to affect native populations by outcompeting, preying upon, and hybridizing with many native aquatic species. This invasive nature via human-mediated introductory has led to their classification in the list of the top 100 globally invasive species.
Since the 19th century, isolated native eastern brook trout populations have faced extirpation due to stream pollution, habitat destruction, invasive species, and waterway damming. Although facing these pressures, the brook trout is not listed as an endangered species by the International Union for Conservation of Nature, but native population decline has been observed.Taxonomy
The scientific name of the brook trout is Salvelinus fontinalis. Initially, the brook trout was scientifically described as Salmo fontinalis by the naturalist Samuel Latham Mitchill in 1814. The species was later moved to the char genus Salvelinus, which in North America also includes the lake trout, bull trout, Dolly Varden, and the Arctic char. The specific epithet "fontinalis" comes from the Latin for "of a spring or fountain", in reference to the clear, cold streams and ponds in its native habitat.Subspecies
There is little recognized systematic substructure in the brook trout, but the two subspecies have been proposed. The aurora trout is a subspecies native to two lakes in the Temiskaming District of Ontario, Canada. The silver trout '' is an extinct trout species or subspecies last seen in Dublin Pond, New Hampshire, in 1930. It is considered by fisheries biologist Robert J. Behnke as a highly specialized form of brook trout.Hybrids
The brook trout produces hybrids both with its congeners the lake trout and the Arctic char, and intergeneric hybrids with the brown trout.
The splake is an intrageneric hybrid between the brook trout and lake trout. Although uncommon in nature, they are artificially propagated in substantial numbers for stocking into brook trout or lake trout habitats. Although they are fertile, back-crossing in nature is behaviorally problematic and very little natural reproduction occurs. Splake grow more quickly than brook trout, become piscivorous sooner, and are more tolerant of competitors than brook trout.
The tiger trout is an intergeneric hybrid between the brook trout and the brown trout. Tiger trout rarely occur naturally but are sometimes artificially propagated. Such crosses are almost always reproductively sterile. They are popular with many fish-stocking programs because they can grow quickly, and may help keep coarse fish populations in check due to their highly piscivorous nature.
The sparctic char is an intrageneric hybrid between the brook trout and the Arctic char.Ecological forms
The United States Forest Service has recognized two ecological forms of brook trout, salters and coasters. The forms express the same general features but vary in size, behavior, and location.Coasters
A potamodromous population of brook trout native to lacustrine regions, which migrate into tributary rivers to spawn, are called "coasters". Coasters tend to be larger than most other populations of brook trout, often reaching 6 to 7 lb in size. They also commonly live for longer periods of time and exhibit more predacious behavior than their counterparts. Many coaster populations have been severely reduced by overfishing and habitat loss by the construction of hydroelectric power dams on Lake Superior tributaries. In Ontario, Michigan, and Minnesota efforts are underway to restore and recover coaster populations.Salters
When Europeans first settled in Eastern North America, semi-anadromous or sea-run brook trout, commonly called "salters", ranged from southern New Jersey, north throughout the Canadian maritime provinces, and west to Hudson Bay. Salters are a short-lived form of brook trout that inhabit smaller bodies of water and exhibit less predacious behavior than coasters. They may spend up to three months at sea feeding on crustaceans, fish, and marine worms in the spring. During this time they won't stray more than a few miles from the river mouth, but then return to freshwater tributaries to spawn in the late summer or autumn. While in saltwater, salters gain a more silvery color, losing much of the distinctive markings seen in freshwater. However, within two weeks of returning to freshwater, they assume typical brook trout color and markings. Salters have faced threats such as habitat destruction, water pollution, and water way damming that have led to their declining population numbers across the Northeastern United States.Description
The brook trout has a dark green to brown color, with a distinctive marbled pattern of lighter shades across the flanks and back and extending at least to the dorsal fin, and often to the tail. A distinctive sprinkling of red dots, surrounded by blue halos, occurs along the flanks. The belly and lower fins are reddish in color, the latter with white leading edges. Often, the belly, particularly of the males, becomes very red or orange when the fish are spawning. Typical lengths of the brook trout vary from, and weights from. The maximum recorded length is and maximum weight. Brook trout can reach at least seven years of age, with reports of 15-year-old specimens observed in California habitats to which the species has been introduced. Growth rates are dependent on season, age, water and ambient air temperatures, and flow rates. In general, flow rates affect the rate of change in the relationship between temperature and growth rate. For example, in spring, growth increased with temperature at a faster rate with high flow rates than with low flow rates.Range and habitat
Brook trout are native to a wide area of Eastern North America, but are increasingly confined to higher elevations southward in the Appalachian Mountains to northern Georgia and northwest South Carolina, Canada from the Hudson Bay basin east, the Great Lakes–Saint Lawrence system, the Canadian maritime provinces, and the upper Mississippi River drainage as far west as eastern Iowa. Their southern historic native range has been drastically reduced, with fish being restricted to higher-elevation, remote streams due to habitat loss and introductions of brown and rainbow trout. As early as 1850, the brook trout's range started to extend west from its native range through introductions. The brook trout was eventually introduced into suitable habitats throughout the western U.S. during the late 19th and early 20th centuries at the behest of the American Acclimatization Society and by private, state, and federal fisheries authorities. Acclimatization movements in Europe, South America, and Oceania resulted in brook trout introductions throughout Europe, in Argentina, and New Zealand. Although not all introductions were successful, a great many established wild, self-sustaining populations of brook trout in non-native waters.Habitat
The brook trout inhabits large and small lakes, rivers, streams, creeks, and spring ponds in cold temperate climates with mild precipitation. Clear spring water with adequate cover and moderate flow rates is indicative of strong habitability for brook trout. They exhibit high levels of adaptability when exposed to habitat changes from environmental effects, and have been observed to exhibit more resilience to habitat change than other Salvelinus species. The typical pH range of brook trout waters is 5.0 to 7.5, with pH extremes of 3.5 to 9.8 possible. Water temperatures typically range from. Warm summer temperatures and low flow rates are stressful on brook trout populations—especially larger fish.Ecology and reproduction
Diet
Brook trout have a diverse diet that includes larval, pupal, adult forms of aquatic insects, adult forms of terrestrial insects that fall into the water, crustaceans, frogs and other amphibians, molluscs, smaller fish, invertebrates, and even small aquatic mammals such as voles and sometimes other young brook trout.Reproduction
The female constructs a depression in a location in the stream bed, sometimes referred to as a "redd", where groundwater percolates upward through the gravel. One or more males approach the female, fertilizing the eggs as the female expresses them. Most spawning involve peripheral males, which directly influences the number of eggs that survive into adulthood. In general, the larger the number of peripheral males present, the more likely the eggs will be cannibalized. The eggs are slightly denser than water. The female then buries the eggs in a small gravel mound where they hatch in 4 to 6 weeks.