Trout are a type of freshwater fish that are found in cold and clear bodies of water such as lakes, rivers, and streams that range from about 50 to 60 °F. This type of fish is generally characterized by having long oval bodies and a long dorsal fin that is covered in different colored spots.
Trout also have cycloid scales, which are smooth, round, and flat. This type of scale grows with the fish, so scientists are actually able to determine the age of a trout by looking at the number of growth rings on a scale. Another characteristic that trout share is that they all spawn in streams.
Despite trout being classified as freshwater fish, there are sea-run trout species that will migrate to the ocean for a part of their lives. Although they may live in the ocean, these marine trout, as well as other species of trout, will make their way to slower-moving streams to lay their eggs on gravel substrate.
Trout Fish Species
1) Cutthroat trout (Oncorhynchus clarkii)
Cutthroat trout have more than 10 subspecies in varying geographic locations, and each subspecies looks slightly different from the other; however, there are characteristics that all of these subspecies share. While coloration varies among different subspecies, all cutthroat trout have red marks on their lower jaws. Cutthroat trout also have teeth on the base of their tongue called basibranchial teeth. Cutthroat trout range from about 7 – 16 inches in length and weigh around 4 – 9 pounds, although the Lahontan cutthroat trout is the largest subspecies, which can weigh up to 40 pounds. There are both anadromous and freshwater cutthroat trout.
Cutthroat trout are largely solitary animals and will only interact with other trout during spawning season. This species of trout is also relatively sedentary, and will only be active to migrate or hunt. Cutthroat trout feed on algae, small crustaceans, and insects when they are young, and adults will feed on just about anything including other fish. Cutthroat trout are not threatened or endangered as a whole species; however, their populations are being threatened by habitat loss as well as the stocking of other trout species like the rainbow trout.
2) Coast rainbow trout (Oncorhynchus mykiss)
Rainbow trout come in two forms: freshwater resident and anadromous. Rainbow trout that reside in freshwater are typically a lighter silver color with intense dark markings along the body, and they have a light pink line running laterally from head to tail. Anadromous rainbow trout, also called steelheads, tend to be a darker silver with less intense spots and a darker line. This darker coloration is believed to help steelheads blend in with the marine environment better. Rainbow trout typically grow between 12 – 20 inches and usually weigh 1 – 4 pounds. This species is also closely related to the cutthroat trout, but unlike cutthroat trout, rainbow trout do not have basibranchial teeth.
Rainbow trout are extremely hostile towards each other as soon as they hatch because only the strongest and largest will be able to outcompete for space and food. Juvenile and adult rainbow trout primarily feed on larvae that float through the water. Relying on this food source saves a lot of energy since they are not actively foraging, but adults will also eat other fish, crustaceans, and worms. Rainbow trout are an incredibly popular sport fish, and this species has been introduced to every continent except for Antarctica. While this species is thriving in certain areas, some populations of steelheads are actually endangered or threatened mainly due to the creation of dams that block access to the steelheads’ spawning streams.
3) Golden trout (Oncorhynchus aguabonita)
Golden trout are a unique species of trout because they only inhabit freshwater lakes and rivers that are at high altitudes ranging from 9,000 – 12,000 feet above sea level. Golden trout get their name because of their golden-yellow bodies complete with orange-red stripes along the body and dark spots around the tail and dorsal fin. This species is one of the smallest species of trout measuring about 6 – 12 inches in length and 0.04 – 11 pounds in weight.
Golden trout are a more social species of trout and can be found swimming in schools. This species is very meek and is easily dominated by any other type of fish, which is why golden trout are only found in remote bodies of water. Golden trout primarily feed on surface-dwelling insects and larvae, and because insects do not survive winters, golden trout have a primary feeding season that lasts from May to September. Golden trout are not currently threatened; however, there have been attempts to increase population sizes, but these attempts do not seem to have long-lasting effects.
4) Gila trout (Oncorhynchus gilae)
Gila trout inhabit freshwater streams and rivers in New Mexico and Arizona. This species grows to about 5 – 9 inches and weighs around 1 – 6 ounces. Their bodies are yellow with spots on the back and adipose fin, and they also have a pinkish lateral band that runs across the body.
Gila trout are generally solitary, and populations tend to have a hierarchy where more aggressive and dominant fish are more likely to push out weaker fish from certain territories. This species is classified as insectivores because they primarily prey on invertebrates around the water, although they have been known to eat other smaller fish when food sources run low. Gila trout are the rarest trout species, and they were once listed as endangered; however there have been many efforts to help reintroduce and repopulate Gila trout in their native waters, and they have been down-listed to being a threatened species in 2006.
5) Apache trout (Oncorhynchus apache)
Apache trout inhabit clear, cool mountain waters in the White Mountain region of Arizona. Apache trout have golden bodies with tints of pink and purple. Dark spots line their backs, and they have a black band through each eye. This species can range from 6 – 24 inches in length and weigh anywhere from 6 ounces to 6 pounds. These fish primarily feed on insects and invertebrates.
Apache trout were once close to extinction due to habitat loss, overfishing, and timber harvesting, but many efforts, starting with the ban of Apache trout fishing implemented by the White Mountain Apache Tribe in 1955, have replenished the species in their native waters.
6) Marble trout (Salmo marmoratus)
Marble trout live in cold streams and rivers that do not get warmer than 60 °F. This species gets its name from its marbled pattern created by brown lines that lay over a silvery-olive body. Many populations of marble trout also have red spots along the lateral line.
Marble trout are a less active species and utilize sit-and-wait and drift-feeding techniques to feed on insects, crustaceans, and fish. They are aggressive competitors and form hierarchies based on dominance. Marble trout are seriously threatened by hybridization with brown trout, and there are believed to be only eight pure marble trout populations left in the wild. These pure populations are monitored today, and efforts are being made to help conserve them.
7) Brown trout (Salmo trutta)
Brown trout prefer to live in slow-moving deep streams, but they are also known to inhabit lakes and marine environments. Brown trout have a brown or olive green body with dark-colored spots, and their undersides are tannish. Adult brown trout range from about 7 – 22 inches in length and weigh anywhere from 1 – 52 pounds. Female brown trout tend to have a larger abdomen and a smaller head compared to males.
Brown trout are very active and sociable fish. Social hierarchies are formed within populations, and the males that exhibit the most assertive behaviors, such as quivering, charging, and biting, will be at the top of the hierarchy. Brown trout primarily feed on invertebrates and crustaceans, but larger individuals will prey on other fish. Brown trout have been introduced to waters all over the world, and they are considered invasive in many areas. While they are a popular sport fish, brown trout seem to be having many negative impacts on ecosystems including the decline of other fish species, as well as the alteration of algal biomass in certain waters.
8) Bull trout (Salvelinus confluentus)
Bull trout are technically members of the char family that reside in cold, clear rivers, lakes, and streams. This species is characterized by olive or blue-gray bodies that have red, yellow, and/or orange spots along the back and sides. The average length for bull trout is 25 inches, and they weigh less than 9 pounds when inhabiting streams.
Juvenile bull trout will feed on small aquatic invertebrates, but as individuals get larger, they are more likely to feed on other fish. Due to habitat loss and habitat degradation, bull trout are listed as a threatened species, but there have been multiple recovery plans implemented to help conserve populations.
9) Lake trout (Salvelinus namaycush)
Lake trout (technically a char species) are mainly found in lakes with very high concentrations of dissolved oxygen, but they are able to survive in deep, cold bodies of water that are low in nutrients. Lake trout have a greenish-colored body that is full of cream-colored spots from the head all the way to the tail, and the lower fins are usually an orange-red color. This species has an average length of 19.7 inches and usually weighs 5 – 15 pounds, but they can get much larger as well.
Lake trout are solitary except during breeding season. They are piscivores, but if this species has to move to deeper water in the warmer summer months to keep cool, they may have to feed entirely on zooplankton. Lake trout are an extremely popular sport fish and have been introduced to waters all over the globe including South America and New Zealand. Lake trout are threatened by overfishing and the predation of sea lampreys, but there are many restocking programs that help maintain the lake trout population.
10) Brook trout (Salvelinus fontinalis)
Brook trout (technically char) can reside in rivers and streams as well as in marine environments, and for each habitat, brook trout have very specific environmental conditions that need to be met in order to survive. Brook trout have a dark green or brown back that fades into silver-colored sides. They have cream-colored wavy lines along their heads and back that turn into spots on their sides, and they also have red and blue spots speckled across their body. Brook trout are around 12 – 20 inches long and weigh 2 – 13 pounds on average.
Brook trout are relatively aggressive fish that tend to live solitary lives, and they will resort to more aggressive behaviors when there is a shortage of food or space, or if there is an unfavorable change in the environment. These fish are opportunistic feeders and will eat just about anything that finds its way into the water including insects, worms, fish, salamanders, and even small rodents. Because brook trout are extremely sensitive to their environment and need perfect conditions to thrive, there are many threats to their populations. Some of the biggest threats include urbanization and climate change, but scientists are working hard to figure out how to help save this species, and efforts are being made to help keep their populations high in number.
11) Tiger trout (Salmo trutta x Salvelinus fontinalis)
Tiger trout are a hybrid species created by crossing a female brook trout and a male brown trout. Because the number of chromosomes of brook trout and brown trout is different, the likelihood of this hybridization occurring naturally is very rare.
Fisheries have been breeding these sterile hybrids and stocking them in bodies of water because they are a unique sport fish, and it is believed that tiger trout can help manage populations of undesirable fish since they are piscivorous. Since these hybrids are not able to reproduce, their populations can be easily managed, making them a much better tool than introducing non-native fish species that can reproduce.
12) Splake (Salvelinus namaycush x Salvelinus fontinalis)
The splake is a hybrid between male brook trout and female lake trout that have been produced in fisheries since the 1870s and regularly stocked in waters in northern North America. Splake look almost identical to brook trout, but the main difference between the two is that splake have a forked caudal fin, whereas brook trout have a square caudal fin.
Because splake grow very rapidly and may not be able to reproduce naturally, fisheries have been stocking splake in water where brook trout were unsuccessful in surviving in an attempt to control populations of other sport fish like bass.
13) Palomino trout (Oncorhynchus mykiss hybrid)
Palomino trout, or golden rainbow trout, is a hybrid species between the rainbow trout and West Virginia golden trout that was created in a West Virginian fishery in the 1950s, and the hybrid was then first stocked in West Virginia in 1963. While these hybrids are not necessarily sterile, the success rate of breeding naturally is unknown.
Palomino trout have golden yellow bodies with a pale belly and contain no spots. Adults can grow to about 12 – 30 inches long and weigh 2 – 10 pounds, and they primarily feed on minnows, aquatic insects, crayfish, and crustaceans. Because of their unique appearance and rarity, palomino trout are a popular sport fish.
