''Oncorhynchus'', from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

ὄγκος (''ónkos''), meaning "bend", and ῥύγχος (''rhúnkhos''), meaning "snout", is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of ray-finned fish in the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Salmoninae of the family Salmonidae, native to coldwater tributaries of the North Pacific basin. The genus contains twelve extant

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, namely six species of Pacific salmon and six species of Pacific trout, all of which are migratory (either anadromous or potamodromous) mid- level predatory fish that display natal homing and semelparity. The name of the genus is derived from

ὄγκος (''ónkos''), meaning "bend", and ῥύγχος (''rhúnkhos''), meaning "snout", in reference to the hooked

secondary sexual characteristic A secondary sex characteristic is a physical characteristic of an organism that is related to or derived from its sex, but not directly part of its reproductive system. In humans, these characteristics typically start to appear during puberty ...

— known as the kype — that the males develop on the lower jaw tip during mating season.

Range

Salmon and trout within ''Oncorhynchus'' are native to the tributaries of the North Pacific Ocean, with their native ranges extend from the

Bering Sea The Bering Sea ( , ; rus, Бе́рингово мо́ре, r=Béringovo móre, p=ˈbʲerʲɪnɡəvə ˈmorʲe) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasse ...

coasts southwards to as far as

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

in the west and

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

in the east, although most of them are distributed in high- latitude cold waters from the Russian Far East to the

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

. In

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, some

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

of cutthroat trout (''O. clarkii'') have become landlocked populations native to

endorheic An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...

waters in the Rocky Mountains and the Great Basin, while others have crossed the Continental Divide to inhabit the

Rio Grande The Rio Grande ( or ) in the United States or the Río Bravo (del Norte) in Mexico (), also known as Tó Ba'áadi in Navajo language, Navajo, is one of the principal rivers (along with the Colorado River) in the Southwestern United States a ...

and western tributaries of the Mississippi River, both of which drain into the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

instead of the Pacific Ocean. Several species of ''Oncorhynchus'', such as the

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...

(''O. mykiss'') and Chinook salmon (''O. tshawytscha''), have been widely introduced into non-native waters around the globe, establishing self-sustaining wild populations. The six Pacific salmons of ''Oncorhynchus'' are anadromous (migratory) and semelparous (die after spawning). Migration can be affected by

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s. Infected individuals can become weak and probably have shortened lifespans. Infection with parasites creates an effect known as culling whereby fish that are infected are less likely to complete the migration. Anadromous forms of ''Oncorhynchus mykiss'' known as steelhead are

iteroparous Semelparity and iteroparity are two contrasting reproductive strategies available to living organisms. A species is considered ''semelparous'' if it is characterized by a single reproduction, reproductive episode before death, and ''iteroparous ...

. The coastal cutthroat trout (''Oncorhynchus clarkii clarkii'') is considered semi-anadromous, as it spends some time in the ocean, usually much closer to its native stream than its fully anadromous relatives.

Evolution

Oncorhynchus rastrosus reconstruction by Ray Troll

Several Late

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

(about 7 million years ago ( Mya)) trout-like fossils in

Idaho Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...

, in the Clarkia Lake beds, appear to be of '' Oncorhynchus''. The presence of these species so far inland established ''Oncorhynchus'' was not only present in the Pacific drainages before the beginning of the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58rainbow and cutthroat trout, and Pacific salmon lineages had diverged before the beginning of the Pliocene. Consequently, the split between ''Oncorhynchus'' and '' Salmo'' (Atlantic salmon) must have occurred well before the Pliocene. Suggested dates have gone back as far as the Early Miocene (about 20 Mya). One fossil species assigned to this genus, '' O. rastrosus'', the spike-toothed salmon ( synonym ''Smilodonichthys''), is a long species known from

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s. The prehistoric species '' O. australis'' (originally described in ''Salmo'') inhabited the Lake Chapala basin of southwestern Mexico during the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

, making it the southernmost known salmonid to have inhabited North America. Speciation among ''Oncorhynchus'' has been examined for decades, and a family "tree" is not yet completely developed for the Pacific salmonids. Mitochondrial DNA (mtDNA) research has been completed on a variety of Pacific trout and salmonid species, but the results do not necessarily agree with fossil research, or molecular research. Chum, pink and sockeye salmon lineages are generally agreed to have diverged in the sequence after other species. Montgomery (2000) discusses the pattern of the fossil record as compared to tectonic shifts in the plates of the

of America. The (potential)

divergence In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the rate that the vector field alters the volume in an infinitesimal neighborhood of each point. (In 2D this "volume" refers to ...

in ''Oncorhynchus'' lineages appear to follow the uprising of the Pacific Rim. The climatic and habitat changes that would follow such a geologic event are discussed, in the context of potential stressors leading to adaptation and speciation. One interesting case involving speciation with salmon is that of the kokanee salmon (landlocked sockeye salmon). Kokanee sockeye evolve differently from anadromous sockeye—they reach the level of "biological species". Biological species—as opposed to morphological species—are defined by the capacity to maintain themselves in sympatry as independent genetic entities. This definition can be vexing because it apparently applies only to sympatry, and this limitation makes the definition difficult to apply. Examples in Washington State,

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, and elsewhere have two populations living in the same lake, but spawning in different substrates at different times, and eating different food sources. There is no pressure to compete or interbreed (two responses when resources are short). These types of kokanee salmon show the principal attributes of a biological species: they are reproductively isolated and show strong resources partitioning.

Decline of ''Oncorhynchus'' populations

A general decline in overall Pacific salmon populations began in the mid-19th century. As the result of western expansion and development in the U.S., experts estimate salmon populations in the Columbia River basin had been reduced to less than 20% of their pre-1850 levels by 1933. In 2008, Lackey estimated that Pacific salmon stocks in the Pacific Northwest were less than 10% of their pre-1850 numbers. Many of the remaining salmon runs are dominated by hatchery-raised salmon, not wild salmon. Many isolated subspecies of the Pacific trouts, particularly those of ''Oncorhynchus mykiss''

and ''Oncorhynchus clarkii'' cutthroat trout have declined in their native ranges. Many local populations or distinct population segments of anadromous forms of steelhead have declined in their native ranges. The resulting declines have resulted in a number of populations of ''Oncorhynchus'' species or subspecies being listed as either endangered, threatened or as "Species of Special Concern" by state, federal or international authorities. Two ''Oncorhynchus clarkii'' subspecies are considered

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

. Declines are attributed to a wide variety of causes—overfishing, habitat loss and degradation, artificial propagation, stocking, and hybridization with or competition with introduced, non-native species. For example, the yellowfin cutthroat trout (''Oncorhynchus clarkii macdonaldi'') is extinct as a result of the introduction of non-native rainbow trout into its native waters. Pacific salmon body size declines are significant and nonlinear

Pacific salmon body size declines are significant and nonlinear

Pacific salmon are facing a widespread decline in body size. The mean body mass of sockeye salmon (''O. nerka'') decreased by 10% between 2000 and 2010. The mean body length of ''Oncorhynchus'' species decreased by 2–8% between 1990 and 2010. Salmon body size is decreasing due to a variety of evolutionary forces, including dams, fishing practices, climate change, and increased competition in the ocean. This trend in salmon size is expected to decrease nutrient cycling and salmon reproductive success while hurting the success of commercial fisheries and rural communities who rely on salmon for survival.

Influence of hatcheries

Declines in the abundance of wild salmon due to over fishing placed greater pressure on hatcheries to increase production and restore the wild salmon stock to supply fisheries. The problem is that hatcheries can never truly replicate the environment of wild salmon, an issue which often results in physiological and behavioral differences between wild salmon and those reared in hatcheries. These differences are often the product of genetic changes associated with inbreeding, artificial selection, and natural selection, as well as different environmental pressures acting on hatchery fish than wild populations. Due to the size selective nature of fishing favoring larger fish, a reduction in average size of the adult salmon has been observed over time. The smaller salmon make a greater proportion of the remaining individuals continuing the population, and problems arise when these hatchery-reared fish are introduced into the wild populations. Unlike wild salmon, larger salmon are selected for in hatcheries and are typically much larger than wild salmon. The result is that hatchery-produced salmon tend to out-compete wild salmon for space, food, and other resources. Some salmon species in hatcheries exhibit predatory behavior toward wild salmon because they grow to be much larger. Regardless of whether predation is observed, natural social interactions are disturbed by the release of large numbers of hatchery-reared salmon where wild populations are low because salmon in hatcheries naturally have a higher propensity towards aggressive behavior. Overall, natural salmon populations are put at risk when hatchery-reared salmon populations are introduced due to competition for resources, predation by larger individuals, and negative social interactions that upset the natural order observed in wild salmon populations. As a result, wild salmon populations are steadily dropping as the pressure to continue breeding salmon in hatcheries increases. Conservation efforts that work to place limitations on hatcheries to increase the wild salmon populations are hindered by financial pressures because hatcheries effectively support many states economically by accounting for over 70% of the salmon harvested for recreational and commercial purposes.

Influence of overfishing

Pacific salmon are harvested throughout the world as a source of food in countries ranging from the United States to South Korea.Groot, Cornelis, and Leo Margolis. (1991) Pacific salmon life histories. UBC press. Over the past century, Pacific salmon have been extensively fished through both recreational,

artisan An artisan (from , ) is a skilled craft worker who makes or creates material objects partly or entirely by hand. These objects may be functional or strictly decorative, for example furniture, decorative art, sculpture, clothing, food ite ...

and commercial fishing. In fact, since the 1970s there has been a nearly threefold increase in catch of Pacific salmon. As this catch has increased, a selection of reduced body size has been observed. In Japanese chum salmon, for example, between 1970 and 1988 there has been a continuous decrease in body weight averaging between 11 and 32 percent. In part, this decline in body weight has been related to the size selective effect of fishing gear used in the harvesting of salmon populations. Salmon of larger body weight are more apt to be caught during fishing efforts, causing lower body weight to be a beneficial character trait for survival. Thus, Pacific salmon have become continuously smaller in body size. However, studies have also shown that for Pacific salmon, a larger mean size at the time of reproduction increases the survival of

offspring In biology, offspring are the young creation of living organisms, produced either by sexual reproduction, sexual or asexual reproduction. Collective offspring may be known as a brood or progeny. This can refer to a set of simultaneous offspring ...

. The life history of salmon favors delayed reproduction because fecundity increased with body size. Consequently, the smaller body size of salmon results in a negative impact on population growth by decreasing the survivability of progeny, and thus decreasing the growth rate of populations. This reduction of productivity in Pacific salmon is, in part, seeded in

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...

and has caused a reduction in population sizes throughout Pacific salmon species. Today, it seems that population numbers of Pacific salmon are on the rise; however, the consequences from the overfishing in the 70s and 80s are still being reflected, with the average body size of salmon being smaller than before the event of overfishing.

Conservation

Canadian efforts

There has been evidence that the sockeye salmon are affected by thermal conditions and their responses to temperature are relatively strong and tend to vary from region to region. Canada has also used the Species at Risk Act to recognize the importance of biological diversity when it comes to the conservation of the salmon population. This means that multiple species of salmon would be looked at when it comes to conservation as well as multiple areas that each species live in. COSEWIC, a Canadian organization for the conservation of species, has named the Interior Fraser River Coho, the Cultus Lake Sockeye, and the Sakinaw Lake Sockeye to all be endangered. In

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

sockeye salmon in four different watersheds were certified by the Marine Stewardship Council, or MSC, as sustainable fisheries in July 2010 and the certification is good for a period of five years. In 2011 MSC also certified the Pink Salmon Fishery and as of 2012 The Chum Salmon Fisheries started their review under the MSC to become certified as a sustainable fishery.Certification Status of Pacific Salmon Fisheries. State of the Salmon. N.p., n.d. Web.

American efforts

The US government has been working to develop a nationwide policy for the salmon populations. The Pacific Salmon Stronghold Conservation Act was re-submitted to congress and if passed will create geographic strongholds for salmon populations.The Salmon Stronghold Initiative. Wild Salmon Center. N.p., n.d. Web. Other policies include the Wild Salmon Policy which was enacted in 2005; its number one focus is the conservation of salmon off of the coasts. Even localized policies have begun, with one in Oregon which focuses on the southernmost watershed and was approved January 2013. In the Alaskan efforts, there is evidence of eight known regional groups of survival. It is also seen that the emigration of smolts (young salmon) from freshwater to other areas such as marine areas have shown significant consequences on the survival of different salmon groups. The Alaska Department of Fish and Game first received MSC, Marine Stewardship Council, Certification in sustainable seafood back in 2000. Each certification is good for a period of five years, with yearly check ups to ensure that the fishery remains sustainable. It was renewed again in 2007, but in 2012 The ADFG left the program. The Annette Island Reserve salmon fishery is under the control of the Metlakatla Indian community and as such was not included in the previous assessments of the Alaskan fisheries. It received its sustainability certification in June 2011. The Wild Salmon Center is a nonprofit organization that works on promoting conservation efforts for salmon worldwide and in the United States; it has helped secure protected watershed areas for Russian and west coast salmon. Other efforts of the Wild Salmon Center include combating illegal fishing, maintaining sustainable fisheries, and creating local watersheds as new habitats.

Russian efforts

Poaching is a threat to ''Oncorhynchus'' salmon and steelhead populations in

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

. It is estimated that illegal catching of salmon is 1.5 times more than the reported catch. The Wild Salmon Center is working with Russian authorities to try to help improve traceability systems so that markets can distinguish between legal sustainable salmon and the illegal salmon. The Wild Salmon Center has secured some of its protected locations for the salmon populations. In efforts with the WWF, the Wild Salmon Center was also able to have a Sockeye Salmon fishery certified as completely sustainable in 2012. The Iturup Island Pink and Chum Salmon Fishery was first certified in 2009 and was the first Russian salmon fishery to receive certification in sustainability by MSC. Other fisheries that were certified by MSC include the Northeast Sakhalin Island Pink Salmon, certified in June 2012, and the Ozernaya River Sockeye Salmon, certified in September 2012. The Aniva Bay Pink Salmon and the Sakhalin Island Pink salmon are both under review by the MSC.

Introductions and aquaculture

Several species of ''Oncorhynchus'' have been successfully introduced into non-native waters, establishing self-sustaining wild populations. The

Rainbow Trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...

''Oncorhynchus mykiss'' is the most widely introduced species of the genus. Rainbow Trout, Chinook Salmon ''Oncorhynchus tshawytscha'' and Coho Salmon ''Oncorhynchus kisutch'' have established wild, self-sustaining populations in the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

and Chinook in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

(known there as quinnat, king or spring salmon). Aquaculture of Chinook and Coho salmon and Rainbow Trout are major industries in

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

and

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. Chinook from Chile were released into Argentinean rivers and there were stockings of Coho and Sockeye Salmon and Rainbow Trout in Patagonia.

Species

Some of the species in this genus are highly variable and a number of now-obsolete taxa have been described. In 1989, morphological and genetic studies by Gerald Smith and Ralph Stearley indicated that trouts of the Pacific basin were genetically closer to Pacific salmon (''Onchorhynchus'' species) than to the '' Salmos'' – brown trout (''Salmo trutta'') or Atlantic salmon (''Salmo salar'') of the Atlantic basin. Thus, in 1989, taxonomic authorities moved the Rainbow, Cutthroat and other Pacific basin trouts into the genus ''Oncorhynchus''.

Extant species

Currently, 12 species and numerous subspecies in this genus are recognized: Behnke (2002).

Fossil species

Based partly on Stearley & Smith: * †'' Oncorhynchus australis'' (Cavender & Miller, 1982) (=''Salmo australis'') - Pleistocene of Jalisco, Mexico (Chapala Formation). * †'' Oncorhynchus belli'' Stearley & Smith, 2018 (Truckee trout) - late Miocene of Nevada ( Truckee Formation). Potentially related to the cutthroat trout. * †'' Oncorhynchus ketopsis'' Eiting & Smith, 2007 - Miocene of Oregon ( Chalk Hills Formation). Likely belonging to the Pacific salmon group. * †'' Oncorhynchus lacustris'' ( Cope, 1870) - late Miocene to late Pliocene of Idaho. Likely belonging to the redband trout group. * †'' Oncorhynchus rastellus'' Stearley & Smith, 2018 (small spiketooth salmon) - Miocene of Idaho (Chalk Hills Formation). Belongs to the Pacific salmon group. * †'' Oncorhynchus rastrosus'' (Cavender & Miller, 1972) (spike-toothed salmon) - middle Miocene to early Pliocene of western North America and Japan. Likely belonging to the Pacific salmon group. * †'' Oncorhynchus salax'' Smith, 1975 - Miocene/Pliocene of Idaho ( Glenns Ferry Formation). Likely belonging to the redband trout group.

Notes

References

* (2002): ''Trout and Salmon of North America''. Free Press, 2002. * (2002): Osteichthyes. ''In:'' A compendium of fossil marine animal genera. ''Bulletin of American Paleontology'' 364: 560
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* (1993): Phylogeny of the Pacific trout and salmon (''Oncorhynchus'') and the genera of family Salmonidae. ''Transactions of the American Fisheries Society'' 122(1): 1–33.
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* (2005) ''The distribution of Pacific salmon (Oncorhynchus spp.) in the Canadian western Arctic''. http://www.dfo-mpo.gc.ca/Library/321160.pdf * *

External links

British Columbia Salmon Farmer's Association

Global Aquaculture AllianceUS mulls Pacific salmon fishing banWatershed Watch Salmon Society
A British Columbia advocacy group for wild salmon

- Watershed Watch Salmon Society. Animated short video based on peer-reviewed scientific research, with subject background article ''Watching out for Wild Salmon''.

- Watershed Watch Salmon Society. Short video documentary. Prominent scientists and First Nation representatives speak their minds about the salmon farming industry and the effects of sea lice infestations on wild salmon populations. {{Authority control Taxa named by George Suckley Ray-finned fish genera Extant Miocene first appearances Biota of the Temperate Northern Pacific