| Brook trout | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Salmoniformes |
| Family: | Salmonidae |
| Genus: | Salvelinus |
| Subgenus: | Baione |
| Species: | S. fontinalis |
| Binomial name | |
| Salvelinus fontinalis (Mitchill, 1814) | |
| Subspecies | |
†S. f. agassizii(Garman, 1885) | |
| Synonyms[3] | |
previous scientific names
| |
Thebrook trout (Salvelinus fontinalis) is aspecies of freshwaterfish in thechargenusSalvelinus of thesalmonfamilySalmonidae native toEastern North America in theUnited States andCanada.[4][2] Two ecological forms of brook trout have been recognized by theUS Forest Service.[4] Oneecological form is long-livedpotamodromous populations inLake Superior known ascoaster trout orcoasters. The second ecological form is the short-livingpredaceousanadromous populations which are found in northern lakes and coastal rivers fromLong Island toHudson Bay, which are referred to assalters.[5] In parts of its range, it is also known as theeastern brook trout,speckled trout,brook char (orcharr),squaretail,brookie, ormud trout, among others.[6] Adult coaster brook trout are capable of reaching sizes over 2 feet in length and weigh up to 6.8 kg (15 lb), whereas adult salters average between 6 and 15 inches in length and weigh between 0.5 and 2.3 kg (1 and 5 lb).[7] The brook trout is characterized by its distinctive olive-green body with yellow and blue-rimmed red spots, white and black edged orangefins, anddorsalvermiculation.[8] The diet of the brook trout is restrictive to the season and location of the fish, but will typically consist of terrestrial andaquatic insects,fry,crustaceans,zooplankton, andworms.[4]
Throughout history, non-native brook trout have been transplanted beyond its native borders, where it has spread acrossNorth America and much of the world.[4] These brook trout have been introduced since the 1800s by means of artificial propagation andaquaculture in hope of promoting fishery resources.[9] Through this transplantation, brook trout have been observed to affect native populations by outcompeting,preying upon, andhybridizing with many nativeaquatic species.[10][11] Thisinvasive nature via human-mediated introductory has led to their classification in thelist of the top 100 globally invasive species.[12]
Since the 19th century, isolated native eastern brook trout populations have facedextirpation due tostream pollution,habitat destruction,invasive species, and waterwaydamming.[13] Although facing these pressures, the brook trout is not listed as anendangered species by theInternational Union for Conservation of Nature, but native population decline has been observed.[14]
The scientific name of the brook trout isSalvelinus fontinalis.[11] Initially, the brook trout was scientifically described asSalmo fontinalis by the naturalistSamuel Latham Mitchill in 1814.[15] The species was later moved to the char genusSalvelinus, which in North America also includes thelake trout,bull trout,Dolly Varden, and theArctic char.[16][15] 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.[17][4]
There is little recognized systematic substructure in the brook trout, but the two subspecies have been proposed. Theaurora trout (S. f. timagamiensis) is a subspecies native to two lakes in theTemiskaming District ofOntario, Canada.[18] Thesilver trout (S. agassizii orS. f. agassizii) is anextinct trout species or subspecies last seen inDublin Pond,New Hampshire, in 1930.[19] It is considered by fisheries biologistRobert J. Behnke as a highly specialized form of brook trout.[20]
The brook trout produceshybrids both with itscongeners thelake trout (S. namaycush) and theArctic char (S. alpinus), and intergeneric hybrids with thebrown trout (Salmo trutta).[21]
Thesplake is an intrageneric hybrid between the brook trout andlake trout (S. namaycush). Although uncommon in nature, they are artificially propagated in substantial numbers for stocking into brook trout or lake trout habitats.[22] Although they arefertile, back-crossing in nature is behaviorally problematic and very little natural reproduction occurs.Splake grow more quickly than brook trout, becomepiscivorous sooner, and are more tolerant of competitors than brook trout.[23]
Thetiger trout is an intergeneric hybrid between the brook trout and the brown trout. Tiger trout rarely occur naturally but are sometimes artificiallypropagated. Such crosses are almost always reproductivelysterile. They are popular with many fish-stocking programs because they can grow quickly, and may help keep coarse fish (wild non "sport" fish) populations in check due to their highly piscivorous (fish-eating) nature.[24]
The sparctic char is an intrageneric hybrid between the brook trout and the Arctic char.[25]
TheUnited States Forest Service has recognized two ecological forms of brook trout,salters andcoasters. The forms express the same general features but vary in size, behavior, and location.[4]
Apotamodromous population of brook trout native tolacustrine regions, whichmigrate intotributary rivers tospawn, are called "coasters".[26] Coasters tend to be larger than most other populations of brook trout, often reaching 6 to 7 lb (2.7 to 3.2 kg) in size.[27] They also commonly live for longer periods of time and exhibit more predacious behavior than their counterparts.[28] Many coaster populations have been severely reduced byoverfishing and habitat loss by the construction ofhydroelectric power dams on Lake Superior tributaries. InOntario,Michigan, andMinnesota efforts are underway to restore and recover coaster populations.[29][30]
When Europeans first settled inEastern North America, semi-anadromous or sea-run brook trout, commonly called "salters", ranged from southernNew Jersey, north throughout theCanadian maritime provinces, and west toHudson Bay. Salters are a short-lived form of brook trout that inhabit smaller bodies of water and exhibit less predacious behavior than coasters.[4] 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 tofreshwatertributaries tospawn 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.[27] Salters have faced threats such ashabitat destruction,water pollution, and water waydamming that have led to their declining population numbers across theNortheastern United States.[31]
The brook trout has a dark green to brown color, with a distinctive marbled pattern (calledvermiculation) of lighter shades across theflanks and back and extending at least to thedorsal 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.[8][4] Typical lengths of the brook trout vary from 25 to 65 cm (9.8 to 25.6 in), and weights from 0.3 to 3 kg (11 oz to 6 lb 10 oz). The maximum recorded length is 86 cm (34 in) and maximum weight 6.6 kg (14 lb 9 oz). Brook trout can reach at least seven years of age, with reports of 15-year-old specimens observed inCalifornia habitats to which the species has been introduced.Growth rates are dependent on season, age, water and ambient air temperatures, andflow 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.[32]
Brook trout are native to a wide area of EasternNorth America, but are increasingly confined to higher elevations southward in theAppalachian Mountains to northernGeorgia and northwestSouth Carolina, Canada from theHudson Bay basin east, theGreat Lakes–Saint Lawrence system, theCanadian maritime provinces, and the upperMississippi River drainage as far west as easternIowa.[34] 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 throughintroductions. 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 theAmerican Acclimatization Society and by private, state, and federal fisheries authorities.[35]Acclimatization movements in Europe, South America, and Oceania resulted in brook trout introductions throughout Europe,[25] inArgentina,[36] andNew Zealand.[37] Although not all introductions were successful, a great many established wild, self-sustaining populations of brook trout in non-native waters.
The brook trout inhabits large and smalllakes,rivers,streams, creeks, and springponds in coldtemperate climates with mildprecipitation.[38] 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 tohabitat change than otherSalvelinus species.[38] The typical pH range of brook trout waters is 5.0 to 7.5, with pH extremes of 3.5 to 9.8 possible.[39] Water temperatures typically range from 34 to 72 °F (1 to 22 °C). Warm summer temperatures and low flow rates are stressful on brook trout populations—especially larger fish.[40]
Brook trout have a diverse diet that includeslarval,pupal, adult forms of aquatic insects (typicallycaddisflies,stoneflies,mayflies, and aquaticdipterans), adult forms of terrestrial insects (typicallyants,beetles,grasshoppers, andcrickets) that fall into the water,crustaceans,frogs and otheramphibians,molluscs, smaller fish, invertebrates, and even small aquatic mammals such asvoles and sometimes other young brook trout.[38]
The female constructs a depression in a location in thestream bed, sometimes referred to as a "redd", wheregroundwater 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.[41] 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.[42]
Following the deposition of up to 5,000 eggs in gravel beds by the female brook trout, the eggs enter an incubation period from the winter months to early spring.[43] During thisincubation period, the eggs source oxygen from the stream that passes through the gravel beds and into theirgel-like shells.[44] The eggs will then successively hatch into miniaturefry that rely upon theiryolk sac for nutrients to compensate for the lack of nutrients provided by the parental trout during the early stages of development. In the ensuing stage of their life cycle, thefry will seek cover frompredatory species in rock crevices and inlets.[43] During this period of hiding, the trout will begin to mature into fingerlings by summer and start expressing parr marks to aid in camouflage.[45] At this point, most brook trout will be between 2 and 3 inches in length.[45] Finally, in succeeding months, the trout will fully mature into a trout that is approximately between 10 and 34 inches long and capable ofspawning in the fall months.[8] These fully developed adult brook trout will express a vibrant olive-green back, cherry red underbelly, black accented fins, and wavydorsal patterns.[46] A typical adult brook trout will live to the age of 3 to 4 years old, with occasional brooks living to over the age of 4.[47]
The brook trout is a popular game fish withanglers, particularlyfly fishermen.[48]
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Until it was displaced by introducedbrown trout (1883) andrainbow trout (1875), the brook trout attracted the most attention of anglers from colonial times through the first 100 years of U.S. history. Sporting writers such as Genio ScottFishing in American Waters (1869), Thaddeus NorrisAmerican Anglers Book (1864),Robert Barnwell RooseveltGame Fish of North America (1864) andCharles HallockThe Fishing Tourist (1873) produced guides to the best-known brook trout waters in America.[51] As brook trout populations declined in the mid-19th century near urban areas, anglers flocked to theAdirondacks in upstate New York and theRangeley lakes region inMaine to pursue brook trout.[51] In July 1916 on theNipigon River in northern Ontario, an Ontario physician, John W. Cook, caught a 14 lb 8 oz (6.57 kg) brook trout, which stands as theIGFA world record.[52]Today, many anglers practicecatch-and-release tactics to preserve remaining populations. Organizations such asTrout Unlimited have been at the forefront of efforts to institute air and water quality standards sufficient to protect the brook trout. Revenues derived from the sale of fishing licenses have been used to restore many sections of creeks and streams to brook trout habitat.[53]
The current world angling record brook trout was caught by Dr. W. J. Cook on the Nipigon River, Ontario, in July 1915. The 31 in (79 cm) trout weighed only 6.57 kg (14 lb 8 oz)[52] because, at the time of weighing, it was badly decomposed after 21 days in the bush without refrigeration.[54][55] A 29 in (74 cm) brook trout, caught in October 2006 in Manitoba, is not eligible for record status since it was released alive.[56][57] This trout weighed about 15.98 lb (7.25 kg) based on the accepted formula for calculating weight by measurements, and it currently stands as the record brook trout forManitoba.[58]
Since the 1800s, brook trout populations have been grown by artificial propagation andaquaculture.[9] Artificial propagation in fish is the process by which eggs areinseminated, hatched, and grown in a controlled environment that minimizes unfavorable environmental pressures. The fish are then released into the wild when they have reached the appropriate age and size.[59][60] This process was introduced as a way to counteract the effects ofoverfishing andaquatic habitat loss and to reinforce brook trout populations across theNortheastern United States.[61] Hatchery rearing was also introduced to raise brook trout in large numbers for food production and sale for human consumption.[62]
In some hatchery programs, mature brook trout are collected from streams usingbackpack electrofishing, a standard fisheries technique that momentarily stuns fish with minimal harm. This allows biologists to safely capturespawning adults, gently express eggs andmilt for fertilization, and return the adult fish to the wild. Both wild and domestic strains of brook trout show no reduction in gamete viability or offspring survival following electrofishing of the adults, supporting this method of collecting offspring for artificial propagation.[63]
Within the hatchery, the process of artificial propagation in brook trout begins by decreasing the temperature of the adult trout's propagation tank to mimic the seasonal changes associated with brook troutspawning season. Theacclimated trout are then collected, and the eggs are gently massaged out of the female trout into a collection vessel, and theninseminated with themilt of a male brook. Next, the inseminated eggs are strained of themilt and transferred to a jar for several weeks to develop into viableembryos. Once the eggs have begun to hatch, thefry are transported into rearing tanks where they will grow and develop before their release into the wild.[64] Their rearing tanks typically consist of large circular tanks with a constant water flow going through them to allow a current to circulate through the tank and keep it clean (some more elaborate systems operate on a re-circulation system where the water is filtered and reused). The fish are typically fed a pelleted food consisting of 40–50% protein and 15% fat made fromfish oil, animal protein, plant protein and vitamins and minerals.[65][66] Finally, once the fish have reached a viable size, around 2 inches in length, they are released into the wild.[64]
This means of brook troutaquaculture has sparked controversy due to potential decrease in the fishes fitness, adaptability, and environmental resilience, effectively posing a threat to native brook trout populations.[61] Arguments against artificial propagation of brook trout claim that it can cause adegradation of the overallgenetic pool due to the possibility ofinbreeding among individuals. This lack ofgenetic variation could lead to certain populations of brook trout to becomeextirpated from their deficiency inadaptability.[9][61]
As early as the late 19th century, native brook trout inNorth America becameextirpated from many watercourses as land development,forest clear-cutting, andindustrialization took hold.[67] Streams and creeks that were polluted, dammed, or silted up often became too warm to hold native brook trout, and were colonized by transplantedsmallmouth bass andperch or other introduced salmonids such as brown andrainbow trout. Thebrown trout, a species not native to North America, has replaced the brook trout in much of the brook trout's native water. If already stressed byoverharvesting or by temperature, brook trout populations are very susceptible to damage by the introduction ofexogenous species. Manylacustrine populations of brook trout have been extirpated by the introduction of other species, particularlypercids, but sometimes otherspiny-rayed fishes.[68]
In addition to chemical pollution and algae growth caused by runoff containing chemicals and fertilizers, air pollution has also been a significant factor in the disappearance of brook trout from their native habitats. In the U.S., acid rain caused by air pollution has resulted in pH levels too low to sustain brook trout in all but the highest headwaters of some Appalachian streams and creeks.[69] Brook trout populations across large parts of eastern Canada have been similarly challenged; a subspecies known as theaurora trout was extirpated from the wild by the effects of acid rain.[70]
Organizations such as Trout Unlimited and Trout Unlimited Canada are partnering with other organizations such as the Southern Appalachian Brook Trout Foundation, the Eastern Brook Trout Joint Venture, and state, provincial, and federal agencies to undertake projects that restore native brook trout habitat and populations.[14][29][71][72]
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Although brook trout populations are under stress in their native range, they are considered aninvasive species where they have been introduced outside their historic native range.[73][74][75] In the northern Rocky Mountains, non-native brook trout are considered a significant contributor to the decline or extirpation of nativecutthroat trout (Oncorhynchus clarki) in headwater streams.[76][77] Invasive brook trout populations may provoke territorial competition with the nativecutthroat trout that can impede the recovery efforts ofcutthroat trout by environmental agencies.[77] Non-native brook trout populations have been subject to eradication programs in efforts to preserve native species.[78][79] InYellowstone National Park, anglers may take an unlimited number of non-native brook trout in some watersheds. In theLamar River watershed, a mandatory kill regulation for any brook trout caught is in effect.[80] In Europe, introduced brook trout, once established, have had negative impacts on growth rates of native brown trout (S. trutta).[25]
{{citation}}:ISBN / Date incompatibility (help)Trout and char of the world | ||
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| Trout of thePacific basin Oncorhynchus | ||
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