Coastal Cutthroat Trout
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The coastal cutthroat trout (''Oncorhynchus clarkii'', sometimes referred as ''Oncorhynchus clarkii clarkii''), also known as the sea-run cutthroat trout, blue-back trout or harvest trout, is one of the four speciesTrotter, Patrick; Bisson, Peter; Roper, Brett; Schultz, Luke; Ferraris, Carl; Smith, Gerald R.; Stearley, Ralph F. (2018), Trotter, Patrick; Bisson, Peter; Shultz, Luke; Roper, Brett (eds.), "A Special Workshop on the Taxonomy and Evolutionary Biology of Cutthroat Trout", ''Cutthroat Trout: Evolutionary Biology and Taxonomy'', American Fisheries Society, , , retrieved 2024-08-12Love Stowell; Metcalf; Markle; Stearly (2018), Trotter; Bisson; Shultz; Roper (eds.), "Species Conceptualization and Delimitation: A Framework for the Taxonomic Revision of Cutthroat Trout", ''Cutthroat Trout: Evolutionary Biology and Taxonomy'', American Fisheries Society, , , retrieved 2024-08-13 of cutthroat trout found in western
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 ...
. The coastal cutthroat trout occurs in four distinct forms. A semi- anadromous or sea-run form is the most well known. Freshwater forms occur in both large and small rivers and streams and lake environments. The native range of the coastal cutthroat trout extends south from the southern coastline of the Kenai Peninsula in
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
to the Eel River in
Northern California Northern California (commonly shortened to NorCal) is a geocultural region that comprises the northern portion of the U.S. state of California, spanning the northernmost 48 of the state's List of counties in California, 58 counties. Northern Ca ...
. Coastal cutthroat trout are resident in tributary streams and rivers of the Pacific basin and are rarely found more than from the ocean. Adults migrate from the ocean to spawn in fresh water. Juveniles migrate to the sea where they feed and become sexually mature before returning to fresh water to overwinter and spawn. Unlike steelhead and Pacific salmon, coastal cutthroat do not make lengthy migrations out to sea. Generally speaking, coastal cutthroat will remain in or near estuarine waters, usually within of their natal stream. Some cutthroat, however, have been shown to move as far as into the open ocean. There are also lacustrine and riverine populations that spend their entire lives in freshwater. One such population is the trout of Lake Crescent in Washington state that was formerly considered to be a separate subspecies called the Lake Crescent cutthroat trout, ''Oncorhynchus clarkii crescenti''.


Taxonomy

Cutthroat trout were given the name ''Salmo clarkii'' in honor of William Clark, who co-led the expedition of 1804–1806. One of Lewis and Clark's missions was to describe the flora and fauna encountered during the expedition. The
type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
of ''S. clarki'' was described by naturalist John Richardson from a tributary of the lower
Columbia River The Columbia River (Upper Chinook language, Upper Chinook: ' or '; Sahaptin language, Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river headwater ...
, identified as the "Katpootl", which was perhaps the Lewis River as there was a Multnomah village of similar name at the
confluence In geography, a confluence (also ''conflux'') occurs where two or more watercourses join to form a single channel (geography), channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main ...
. This type specimen was most likely the coastal cutthroat subspecies. In 1989, morphological and genetic studies by Gerald R. Smith, the Curator of Fishes at the Museum of Zoology, and Ralph F. Stearley, a doctoral candidate at Museum of Paleontology (
University of Michigan The University of Michigan (U-M, U of M, or Michigan) is a public university, public research university in Ann Arbor, Michigan, United States. Founded in 1817, it is the oldest institution of higher education in the state. The University of Mi ...
) indicated trout of the Pacific basin were genetically closer to Pacific salmon (''Oncorhynchus'' species) than to the ''
Salmo ''Salmo'' is a genus of ray-finned fish from the subfamily Salmoninae of family (biology), family Salmonidae, and is part of the tribe (biology), tribe Salmonini along with the sister genera ''Salvelinus'' and ''Salvethymus''. Almost all ''Salmo ...
''s– brown trout (''S. trutta'') or
Atlantic salmon The Atlantic salmon (''Salmo salar'') is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Hucho taimen, Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlan ...
(''S. salar'') of the Atlantic basin. Thus, in 1989, taxonomic authorities moved the rainbow, cutthroat and other Pacific basin trout into the genus ''Oncorhynchus''. Since diversion with the ancestor of the various cutthroat species 2.66 million years ago, the modern Coastal cutthroat trout has remained relatively unchanged. Formerly, Coastal cutthroat trout were lumped together as one species with multiple subspecies, but newer evidence supports a framework of four full species (with multiple subspecies), including the Coastal cutthroat trout.


Description

Freshwater forms of the coastal cutthroat trout are generally dark green to greenish-blue on back, olive-green on upper flank, silvery on lower flank and belly. They display more numerous flank spots below lateral line, irregular spots on dorsal, adipose and caudal fins and the anal, pectoral and pelvic fin bases. The gill covers are pinkish. Sea-run forms while in salt water and shortly after returning to fresh water are silvery with a bluish back, yellowish lower flanks and fins, and display sparse spots. Cutthroats usually display distinctive red, pink, or orange linear marks along the undersides of their
mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...
s in the lower folds of the
gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...
plates. These markings are responsible for the common name "cutthroat" given to the trout by outdoor writer Charles Hallock in an 1884 article in ''The American Angler''., although the red slashes are not unique to the cutthroat trout and some coastal rainbow trout and redband trout also display throat slashes. The sea-run forms of coastal cutthroat average , while stream-resident forms attain much smaller sizes .


Lifecycle

Coastal cutthroat trout usually inhabit and spawn in small to moderately large, clear, well- oxygenated, shallow rivers with gravel bottoms. They are native to the alluvial or freestone streams that are typical tributaries of the Pacific Basin. They typically spawn from December through June, with peak spawning in February. Eggs begin to hatch within six to seven weeks of spawning. Spawning begins when water temperatures reach . Depending on temperature, alevins emerge as fry between March and June, with peak emergence in mid-April. Lake-resident coastal cutthroat trout are usually found in moderately deep, cool lakes with adequate shallows and vegetation for good food production. Lake populations generally require access to gravel-bottomed streams to be self-sustaining, but occasionally spawn on shallow gravel beds with good water circulation. Cutthroat trout naturally interbreed with the closely related rainbow trout, producing fertile hybrids commonly called " cutbows" although this is a much rarer occurrence with the coastal cutthroat trout because of reproductive isolation as the coastal cutthroat trout is the only cutthroat subspecies to coevolve through its entire range with the coastal rainbow trout (''O. mykiss irideus''). As this hybrid generally bears similar coloration and overall appearance to the cutthroat, retaining the characteristic orange-red slash, these hybrids often pose a taxonomic difficulty.


Range and habitat

The native range of the coastal cutthroat trout extends south from the southern coastline of the Kenai Peninsula in
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
to the Eel River in Northern
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
. Coastal cutthroat trout are resident in tributary streams and rivers of the Pacific basin and are rarely found more than from the ocean. Semi-anadromous, stream resident, fluvial and lake resident forms exist. The great majority of coastal cutthroat trout habitat coincides with the belt of Pacific coast coniferous rainforest that extends from Alaska southward into Northern California. Coastal cutthroat trout use a large variety of habitat types, including lower and upper reaches of both large and small river systems, urban environments, estuaries, sloughs, ponds, lakes, and near shore ocean waters. They spend more time in fresh water environments than other anadromous Pacific salmonids. In fresh water they prefer deeper pool habitat and cover, such as that formed by woody debris. The semi-anadromous forms of coastal cutthroat trout do not overwinter in saltwater and rarely make extended migrations across large bodies of water. Migrations in the marine environment are usually within of land. Semi-anadromous coastal cutthroat typically spend two to five years rearing in fresh water before making their initial migration into saltwater. Generally, semi-anadromous coastal cutthroat trout spend short periods offshore during summer months and return to estuaries and fresh water by fall or winter.


Conservation status

The coastal cutthroat is a secure subspecies of the cutthroat trout. Although there has been a general population decline of the sea-run form throughout its native range since the 19th century, none of the populations in the United States or British Columbia are considered threatened or endangered. The U.S. Fish and Wildlife Service, in cooperation with the U.S. Environmental Protection Agency, National Marine Fisheries Service and state wildlife agencies has designated ten distinct population segments (DPS) from Alaska to California. A comprehensive status review of the DPSs in 1999 determined that only one DPS, the Southwestern Washington/Columbia River DPS be proposed for threatened status under the
Endangered Species Act The Endangered Species Act of 1973 (ESA; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting and conserving imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of e ...
. On July 5, 2002, after lengthy public comment and scientific evaluation, the U.S. Fish and Wildlife service withdrew its proposal to list the Southwestern Washington/Columbia River DPS as threatened.Bateman, D.S., R.E. Gresswell, D. Warren, D.P. Hockman-Wert., D.W. Leer, J.T. Light and J.D. Stednick. 2018. Fish response to contemporary timber harvest practices in a second-growth forest from the central Coast Range of Oregon. Forest Ecology and Management 411: 142–157. Stream resident, fluvial and lake forms are secure within their native range and supplemented by stocking of hatchery raised fish in Washington and Oregon.


References


Further reading

* * * * * {{DEFAULTSORT:trout, cutthroat, coastal coastal cutthroat trout Cold water fish Game fish Fish of Canada Fish of the Western United States Fauna of the Northwestern United States coastal cutthroat trout