The cutthroat trout is a fish species of the family Salmonidae native to cold-water tributaries of the Pacific Ocean, Rocky Mountains, Great Basin in North America. As a member of the genus Oncorhynchus, it is one of the Pacific trout, a group that includes the distributed rainbow trout. Cutthroat trout are popular gamefish among anglers who enjoy fly fishing; the common name "cutthroat" refers to the distinctive red coloration on the underside of the lower jaw. The specific name clarkii was given to honor explorer William Clark, coleader of the Lewis and Clark Expedition. Cutthroat trout inhabit and spawn in small to moderately large, well-oxygenated, shallow rivers with gravel bottoms, they reproduce in clear, moderately deep lakes. They are native to the alluvial or freestone streams that are typical tributaries of the rivers of the Pacific basin, Great Basin and Rocky Mountains. Cutthroat trout spawn in the spring and may inadvertently but hybridize with rainbow trout, producing fertile cutbows.
Some populations of the coastal cutthroat trout are semi-anadromous. Several subspecies of cutthroat trout are listed as threatened in their native ranges due to habitat loss and the introduction of non-native species. Two subspecies, O. c. alvordensis and O. c. macdonaldi, are considered extinct. Cutthroat trout are raised in hatcheries to restore populations in their native range, as well as stock non-native lake environments to support angling; the cutthroat trout type species and several subspecies are the official state fish of seven western U. S. states. The scientific name of the cutthroat trout is Oncorhynchus clarkii. Cutthroat trout were the first New World trout encountered by Europeans when in 1541, Spanish explorer Francisco de Coronado recorded seeing trout in the Pecos River near Santa Fe, New Mexico; these were most Rio Grande cutthroat trout The species was first described in the journals of explorer William Clark from specimens obtained during the Lewis and Clark Expedition from the Missouri River near Great Falls and these were most the westslope cutthroat trout.
As one of Lewis and Clark's many missions was to describe the flora and fauna encountered during their expedition, cutthroat trout were given the name Salmo clarkii in honor of William Clark. In 1836, the type specimen of S. clarkii was described by naturalist John Richardson from a tributary of the lower Columbia River, identified as the "Katpootl", the Lewis River as there was a Multnomah village of similar name at the confluence. This type specimen was most the coastal cutthroat trout subspecies O. c. clarkii. Until the 1960s, populations of westslope cutthroat trout and Yellowstone cutthroat trout were lumped into one subspecies. Biologists split the group into two subspecies, christening the name westslope cutthroat trout with the lewisii name which honors explorer Meriwether Lewis and renaming the Yellowstone cutthroat trout Salmo bouvierii, the first name given to the Yellowstone cutthroat trout by David Starr Jordan in 1883 honoring a U. S. Army Captain Bouvier. In 1989, morphological and genetic studies indicated trout of the Pacific basin were genetically closer to Pacific salmon than to the Salmos–brown trout or Atlantic salmon of the Atlantic basin.
Thus, in 1989, taxonomic authorities moved the rainbow and other Pacific basin trout into the genus Oncorhynchus. Behnke in his salmon and trout handbook of 2002 recognized 14 subspecies of cutthroat trout that are each native to a separate geographic area. Not all of them were scientifically described, different views on the taxonomic identities have been presented in some cases, it has been suggested that the cutthroat trout evolved from a common Oncorhynchus ancestor that migrated along the Pacific coast and into the mountain west via the Columbia and Snake river basins 3-5 million years ago, in the late Pliocene or early Pleistocene epochs. These epochs had repeated glacial and interglacial periods that would have caused repeated fracturing and isolation of cutthroat trout populations resulting in the different subspecies found today; the 14 subspecies are found in four evolutionary groups—Coastal, Westslope and Lahontan. Throughout their native and introduced ranges, cutthroat trout vary in size and habitat selection.
Their coloration can range from golden to gray to green on the back. Cutthroat trout can be distinguished from rainbow trout by the presence of basibranchial teeth at the base of tongue and a maxillary that extends beyond the posterior edge of the eye. Depending on subspecies and habitat, most have distinctive red, pink, or orange linear marks along the underside of their mandibles in the lower folds of the gill plates; these markings are responsible for the common name "cutthroat", first given to the trout by outdoor writer Charles Hallock in an 1884 article in The American Angler. These markings are not unique to the species, some coastal rainbow trout and Columbia River redband trout populations display reddish or pink throat markings. At maturity, different populations and subspecies of cutthroat trout can range from 6 to 40 inches in length, depending on habitat and food availability. Sea-run forms of coastal cutthroat trout average 2 to 5 pounds; the length and weights of mature inland forms vary depending on their particular environment and availability of food.
Stream-resident fish are much smaller, 0.4 to 3.2 ounces, while lacustrine populations have attained weights ranging from 12 to
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
The teleosts or Teleostei are by far the largest infraclass in the class Actinopterygii, the ray-finned fishes, make up 96% of all extant species of fish. Teleosts are arranged into 448 families. Over 26,000 species have been described. Teleosts range from giant oarfish measuring 7.6 m or more, ocean sunfish weighing over 2 t, to the minute male anglerfish Photocorynus spiniceps, just 6.2 mm long. Including not only torpedo-shaped fish built for speed, teleosts can be flattened vertically or horizontally, be elongated cylinders or take specialised shapes as in anglerfish and seahorses. Teleosts dominate the seas from pole to pole and inhabit the ocean depths, rivers and swamps; the difference between teleosts and other bony fish lies in their jaw bones. This is of great advantage, enabling them to draw it into the mouth. In more derived teleosts, the enlarged premaxilla is the main tooth-bearing bone, the maxilla, attached to the lower jaw, acts as a lever and pulling the premaxilla as the mouth is opened and closed.
Other bones further back in the mouth serve to swallow food. Another difference is that lower lobes of the tail fin are about equal in size; the spine ends at the caudal peduncle, distinguishing this group from other fish in which the spine extends into the upper lobe of the tail fin. Teleosts have adopted a range of reproductive strategies. Most use external fertilisation: the female lays a batch of eggs, the male fertilises them and the larvae develop without any further parental involvement. A fair proportion of teleosts are sequential hermaphrodites, starting life as females and transitioning to males at some stage, with a few species reversing this process. A small percentage of teleosts are viviparous and some provide parental care with the male fish guarding a nest and fanning the eggs to keep them well-oxygenated. Teleosts are economically important to humans, as is shown by their depiction in art over the centuries; the fishing industry harvests them for food, anglers attempt to capture them for sport.
Some species are farmed commercially, this method of production is to be important in the future. Others are kept in aquariums or used in research in the fields of genetics and developmental biology. Distinguishing features of the teleosts are mobile premaxilla, elongated neural arches at the end of the caudal fin and unpaired basibranchial toothplates; the premaxilla is unattached to the neurocranium. This lowers the pressure inside the mouth; the lower jaw and maxilla are pulled back to close the mouth, the fish is able to grasp the prey. By contrast, mere closure of the jaws would risk pushing food out of the mouth. In more advanced teleosts, the premaxilla has teeth, while the maxilla is toothless; the maxilla functions to push both the lower jaw forward. To open the mouth, an adductor muscle pulls back the top of the maxilla, pushing the lower jaw forward. In addition, the maxilla rotates which pushes forward a bony process that interlocks with the premaxilla; the pharyngeal jaws of teleosts, a second set of jaws contained within the throat, are composed of five branchial arches, loops of bone which support the gills.
The first three arches include a single basibranchial surrounded by two hypobranchials, ceratobranchials and pharyngobranchials. The median basibranchial is covered by a toothplate; the fourth arch is composed of pairs of ceratobranchials and epibranchials, sometimes additionally, some pharyngobranchials and a basibranchial. The base of the lower pharyngeal jaws is formed by the fifth ceratobranchials while the second and fourth pharyngobranchials create the base of the upper. In the more basal teleosts the pharyngeal jaws consist of well-separated thin parts that attach to the neurocranium, pectoral girdle, hyoid bar, their function is limited to transporting food, they rely on lower pharyngeal jaw activity. In more derived teleosts the jaws are more powerful, with left and right ceratobranchials fusing to become one lower jaw, they have developed a muscle that allows the pharyngeal jaws to have a role in grinding food in addition to transporting it. The caudal fin is homocercal, meaning the upper and lower lobes are about equal in size.
The spine ends at the caudal peduncle, the base of the caudal fin, distinguishing this group from those in which the spine extends into the upper lobe of the caudal fin, such as most fish from the Paleozoic. The neural arches are elongated to form uroneurals. In addition, the hypurals, bones that form a flattened plate at the posterior end of the vertebral column, are enlarged providing further support for the caudal fin. In general, teleosts tend to be more flexible than more basal bony fishes, their skeletal structure has evolved towards greater lightness. While teleost bones are well calcified, they are constructed from a scaffolding of struts, rather than the dense cancellous bones of holostean fish. In addition, the lower jaw of the teleost is reduced to just three bones; the teleosts were first recognised as a distinct group by the G
Salmon is the common name for several species of ray-finned fish in the family Salmonidae. Other fish in the same family include trout, char and whitefish. Salmon are native to tributaries of the North Pacific Ocean. Many species of salmon have been introduced into non-native environments such as the Great Lakes of North America and Patagonia in South America. Salmon are intensively farmed in many parts of the world. Salmon are anadromous: they hatch in fresh water, migrate to the ocean return to fresh water to reproduce. However, populations of several species are restricted to fresh water through their lives. Folklore has it. Tracking studies have shown this to be true. A portion of a returning salmon run may spawn in different freshwater systems. Homing behavior has been shown to depend on olfactory memory. Salmon date back to the Neogene; the term "salmon" comes from the Latin salmo, which in turn might have originated from salire, meaning "to leap". The nine commercially important species of salmon occur in two genera.
The genus Salmo contains the Atlantic salmon, found in the north Atlantic, as well as many species named trout. The genus Oncorhynchus contains eight species which occur only in the North Pacific; as a group, these are known as Pacific salmon. Chinook salmon have been introduced in New Patagonia. Coho, freshwater sockeye, Atlantic salmon have been established in Patagonia, as well. † Both the Salmo and Oncorhynchus genera contain a number of species referred to as trout. Within Salmo, additional minor taxa have been called salmon in English, i.e. the Adriatic salmon and Black Sea salmon. The steelhead anadromous form of the rainbow trout migrates to sea, but it is not termed "salmon". A number of other species have common names which refer to them as being salmon. Of those listed below, the Danube salmon or huchen is a large freshwater salmonid related to the salmon above, but others are marine fishes of the unrelated Perciformes order: Eosalmo driftwoodensis, the oldest known salmon in the fossil record, helps scientists figure how the different species of salmon diverged from a common ancestor.
The British Columbia salmon fossil provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis of mitochondrial DNA suggest the divergence occurred by 10 to 20 million years ago; this independent evidence from DNA analysis and the fossil record rejects the glacial theory of salmon divergence. Atlantic salmon reproduce in northern rivers on both coasts of the Atlantic Ocean. Landlocked salmon live in a number of lakes in eastern North America and in Northern Europe, for instance in lakes Sebago, Ladoga, Saimaa, Vänern, Winnipesaukee, they are not a different species from the Atlantic salmon, but have independently evolved a non-migratory life cycle, which they maintain when they could access the ocean. Chinook salmon are known in the United States as king salmon or blackmouth salmon, as spring salmon in British Columbia. Chinook are the largest of all Pacific salmon exceeding 14 kg; the name tyee is used in British Columbia to refer to Chinook over 30 pounds, in the Columbia River watershed large Chinook were once referred to as June hogs.
Chinook salmon are known to range as far north as the Mackenzie River and Kugluktuk in the central Canadian arctic, as far south as the Central California coast. Chum salmon are known as dog, keta, or calico salmon in some parts of the US; this species has the widest geographic range of the Pacific species: south to the Sacramento River in California in the eastern Pacific and the island of Kyūshū in the Sea of Japan in the western Pacific. Coho salmon are known in the US as silver salmon; this species is found throughout the coastal waters of Alaska and British Columbia and as far south as Central California. It is now known to occur, albeit infrequently, in the Mackenzie River. Masu salmon or cherry salmon are found only in the western Pacific Ocean in Japan and Russia. A land-locked subspecies known as the Taiwanese salmon or Formosan salmon is found in central Taiwan's Chi Chia Wan Stream. Pink salmon, known as humpies in southeast and southwest Alaska, are found from northern California and Korea, throughout the northern Pacific, from the Mackenzie River in Canada to the Lena River in Siberia in shorter coastal streams.
It is the smallest of the Pacific species, with an average weight of 1.6 to 1.8 kg. Sockeye salmon are known in the US as red salmon; this lake-rearing species is found south as far as the Klamath River in California in the eastern Pacific and northern Hokkaidō island in Japan in the western Pacific and as far north as Bathurst Inlet in the Canadian Arctic in the east and the Anadyr River in Siberia in the west. Although most adult Pacific salmon feed on small fish and squid, sockeye feed on plankton they filter through gill rakers. Kokanee salmon are the land-locked form of sockeye salmon. Danube salmon, or huchen, are the largest permanent freshwater salmonid species. Salmon eggs are laid in freshwater streams at high latitudes; the eggs hatch into alevin or sac fry
The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles and archosaurs; the world at the time was dominated by two continents known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors; the Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earth's history, in which nearly 96% of marine species and 70% of terrestrial species died out.
It would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian–Triassic extinction event was protracted; the term "Permian" was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Édouard de Verneuil; the region now lies in the Perm Krai of Russia. Official ICS 2017 subdivisions of the Permian System from most recent to most ancient rock layers are: Lopingian epoch Changhsingian Wuchiapingian Others: Waiitian Makabewan Ochoan Guadalupian epoch Capitanian stage Wordian stage Roadian stage Others: Kazanian or Maokovian Braxtonian stage Cisuralian epoch Kungurian stage Artinskian stage Sakmarian stage Asselian stage Others: Telfordian Mangapirian Sea levels in the Permian remained low, near-shore environments were reduced as all major landmasses collected into a single continent—Pangaea; this could have in part caused the widespread extinctions of marine species at the end of the period by reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major landmasses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean, the Paleo-Tethys Ocean, a large ocean that existed between Asia and Gondwana; the Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys Ocean to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic era. Large continental landmass interiors experience climates with extreme variations of heat and cold and monsoon conditions with seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea; such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian. Three general areas are noted for their extensive Permian deposits—the Ural Mountains and the southwest of North America, including the Texas red beds.
The Permian Basin in the U. S. states of Texas and New Mexico is so named because it has one of the thickest deposits of Permian rocks in the world. The climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an ice age. Glaciers receded around the mid-Permian period as the climate warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles. Permian marine deposits are rich in fossil mollusks and brachiopods. Fossilized shells of two kinds of invertebrates are used to identify Permian strata and correlate them between sites: fusulinids, a kind of shelled amoeba-like protist, one of the foraminiferans, ammonoids, shelled cephalopods that are distant relatives of the modern nautilus. By the close of the Permian, trilobites and a host of other marine groups became extinct. Terrestrial life in the Permian included diverse plants, fungi and various types of tetrapods; the period saw a massive desert covering the interior of Pangaea.
The warm zone spread in the northern hemisphere. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals became marginal elements; the Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began; the swamp-loving
Trout is the common name for a number of species of freshwater fish belonging to the genera Oncorhynchus and Salvelinus, all of the subfamily Salmoninae of the family Salmonidae. The word trout is used as part of the name of some non-salmonid fish such as Cynoscion nebulosus, the spotted seatrout or speckled trout. Trout are related to salmon and char: species termed salmon and char occur in the same genera as do fish called trout. Lake trout and most other trout live in freshwater lakes and rivers while there are others, such as the steelhead, which can spend two or three years at sea before returning to fresh water to spawn. Steelhead that live out their lives in fresh water are called rainbow trout. Arctic char and brook trout are part of the char family. Trout are an important food source for humans and wildlife, including brown bears, birds of prey such as eagles, other animals, they are classified as oily fish. The name'trout' is used for some species in three of the seven genera in the subfamily Salmoninae: Salmo, Atlantic species.
Fish referred to as trout include: Genus Salmo Adriatic trout, Salmo obtusirostris Brown trout, Salmo trutta River trout, S. t. morpha fario Lake trout/Lacustrine trout, S. t. morpha lacustris Sea trout, S. t. morpha trutta Flathead trout, Salmo platycephalus Marble trout, Soca River trout or Soča trout – Salmo marmoratus Ohrid trout, Salmo letnica, S. balcanicus, S. lumi, S. aphelios Sevan trout, Salmo ischchan Genus Oncorhynchus Biwa trout, Oncorhynchus masou rhodurus Cutthroat trout, Oncorhynchus clarki Coastal cutthroat trout, O. c. clarki Crescenti trout, O. c. c. f. crescenti Alvord cutthroat trout O. c. alvordensis Bonneville cutthroat trout O. c. utah Humboldt cutthroat trout O. c. humboldtensis Lahontan cutthroat trout O. c. henshawi Whitehorse Basin cutthroat trout Paiute cutthroat trout O. c. seleniris Snake River fine-spotted cutthroat trout, O. c. behnkei Westslope cutthroat trout O. c. lewisi Yellowfin cutthroat trout O. c. macdonaldi Yellowstone cutthroat trout O. c. bouvieri Colorado River cutthroat trout O. c. pleuriticus Greenback cutthroat trout O. c. stomias Rio Grande cutthroat trout O. c. virginalis Oncorhynchus gilae Gila trout, O. g. gilae Apache trout, O. g. apache Rainbow trout, Oncorhynchus mykiss Kamchatkan rainbow trout, Oncorhynchus mykiss mykiss Columbia River redband trout, Oncorhynchus mykiss gairdneri Coastal rainbow trout, Oncorhynchus mykiss irideus Beardslee trout, Oncorhynchus mykiss irideus var. beardsleei Great Basin redband trout, Oncorhynchus mykiss newberrii Golden trout, Oncorhynchus mykiss aguabonita Kern River rainbow trout, Oncorhynchus mykiss aguabonita var. gilberti Sacramento golden trout, Oncorhynchus mykiss aguabonita var. stonei Little Kern golden trout, Oncorhynchus mykiss aguabonita var. whitei Kamloops rainbow trout, Oncorhynchus mykiss kamloops Baja California rainbow trout, Nelson's trout, or San Pedro Martir trout, Oncorhynchus mykiss nelsoni Eagle Lake trout, Oncorhynchus mykiss aquilarum McCloud River redband trout, Oncorhynchus mykiss stonei Sheepheaven Creek redband trout Mexican golden trout, Oncorhynchus chrysogaster Genus Salvelinus Brook trout, Salvelinus fontinalis Aurora trout, S. f. timagamiensis Bull trout, Salvelinus confluentus Dolly Varden trout, Salvelinus malma Lake trout, Salvelinus namaycush Silver trout, † Salvelinus agassizi Hybrids Tiger trout, Salmo trutta X Salvelinus fontinalis Speckled Lake trout, Salvelinus namaycush X Salvelinus fontinalis Trout that live in different environments can have different colorations and patterns.
These colors and patterns form as camouflage, based on the surroundings, will change as the fish moves to different habitats. Trout in, or newly returned from the sea, can look silvery, while the same fish living in a small stream or in an alpine lake could have pronounced markings and more vivid coloration. In general trout that are about to breed have intense coloration, they can look like an different fish outside of spawning season. It is impossible to define a particular color pattern as belonging to a specific breed. Trout have fins without spines, all of them have a small adipose fin along the back, near the tail; the pelvic fins sit well back on each side of the anus. The swim bladder is connected to the esophagus, allowing for gulping or rapid expulsion of air, a condition known as physostome. Unlike many other physostome fish, trout do not use their bladder as an auxiliary device for oxygen uptake, relying on their gills. There are many species, more populations, that are isolated from each other and morphologically different.
However, since many of these distinct populations show no significant genetic differences, what may appear to be a large number of species is considered a much smaller number of distinct species by most ichthyologists. The trout found in the eastern United States are a good example of this; the brook trout, the aurora trout, the silver trout all have physical characteristics and colorations that distinguish them, yet genetic analysis shows that they are one species, Salvelinus fontinalis. Lake trout, like brook trout, belong to the char genus. Lake trout inhabit many of the larger lakes in North America, live m
The rainbow trout is a trout and species of salmonid native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead is an anadromous form of the coastal rainbow trout or Columbia River redband trout that returns to fresh water to spawn after living two to three years in the ocean. Freshwater forms that have been introduced into the Great Lakes and migrate into tributaries to spawn are called steelhead. Adult freshwater stream rainbow trout average between 1 and 5 lb, while lake-dwelling and anadromous forms may reach 20 lb. Coloration varies based on subspecies and habitat. Adult fish are distinguished by a broad reddish stripe along the lateral line, from gills to the tail, most vivid in breeding males. Wild-caught and hatchery-reared forms of this species have been transplanted and introduced for food or sport in at least 45 countries and every continent except Antarctica. Introductions to locations outside their native range in the United States, Southern Europe, New Zealand and South America have damaged native fish species.
Introduced populations may affect native species by preying on them, out-competing them, transmitting contagious diseases, or hybridizing with related species and subspecies, thus reducing genetic purity. The rainbow trout is included in the list of the top 100 globally invasive species. Nonetheless, other introductions into waters devoid of any fish species or with depleted stocks of native fish have created sport fisheries such as the Great Lakes and Wyoming's Firehole River; some local populations of specific subspecies, or in the case of steelhead, distinct population segments, are listed as either threatened or endangered under the Endangered Species Act. The steelhead is the official state fish of Washington; the scientific name of the rainbow trout is Oncorhynchus mykiss. The species was named by German naturalist and taxonomist Johann Julius Walbaum in 1792 based on type specimens from the Kamchatka Peninsula in Siberia. Walbaum's original species name, was derived from the local Kamchatkan name used for the fish, mykizha.
The name of the genus is from the Greek onkos and rynchos, in reference to the hooked jaws of males in the mating season. Sir John Richardson, a Scottish naturalist, named a specimen of this species Salmo gairdneri in 1836 to honor Meredith Gairdner, a Hudson's Bay Company surgeon at Fort Vancouver on the Columbia River who provided Richardson with specimens. In 1855, William P. Gibbons, the curator of Geology and Mineralogy at the California Academy of Sciences, found a population and named it Salmo iridia corrected to Salmo irideus; these names faded once it was determined that Walbaum's description of type specimens was conspecific and therefore had precedence. In 1989, morphological and genetic studies indicated that trout of the Pacific basin were genetically closer to Pacific salmon than to the Salmos – brown trout or Atlantic salmon of the Atlantic basin. Thus, in 1989, taxonomic authorities moved the rainbow and other Pacific basin trout into the genus Oncorhynchus. Walbaum's name had precedence, so the species name Oncorhynchus mykiss became the scientific name of the rainbow trout.
The previous species names irideus and gairdneri were adopted as subspecies names for the coastal rainbow and Columbia River redband trout, respectively. Anadromous forms of the coastal rainbow trout or redband trout are known as steelhead. Subspecies of Oncorhynchus mykiss are listed below as described by fisheries biologist Robert J. Behnke. Resident freshwater rainbow trout adults average between 1 and 5 lb in riverine environments, while lake-dwelling and anadromous forms may reach 20 lb. Coloration varies between regions and subspecies. Adult freshwater forms are blue-green or olive green with heavy black spotting over the length of the body. Adult fish have a broad reddish stripe along the lateral line, from gills to the tail, most pronounced in breeding males; the caudal fin is only mildly forked. Lake-dwelling and anadromous forms are more silvery in color with the reddish stripe completely gone. Juvenile rainbow trout display parr marks typical of most salmonid juveniles. In some redband and golden trout forms parr marks are retained into adulthood.
Some coastal rainbow trout and Columbia River redband trout populations and cutbow hybrids may display reddish or pink throat markings similar to cutthroat trout. In many regions, hatchery-bred trout can be distinguished from native trout via fin clips. Fin clipping the adipose fin is a management tool used to identify hatchery-reared fish. Rainbow trout, including steelhead forms spawn in early to late spring when water temperatures reach at least 42 to 44 °F; the maximum recorded lifespan for a rainbow trout is 11 years. Freshwater resident rainbow trout inhabit and spawn in small to moderately large, well oxygenated, shallow rivers with gravel bottoms, they are native to the alluvial or freestone streams that are typical tributaries of the Pacific basin, but introduced rainbow trout have established wild, self-sustaining populations in other river types such as bedrock and spring creeks. Lake resident rainbow trout are found in moderately deep, cool lakes with