Oncorhynchus kawamurae, the black kokanee, or kunimasu in Japanese,^[1] is a Japanese taxon of salmon which was thought had gone extinct in 1940, but was discovered to still have a living population in 2010.^[1]

Oncorhynchus kawamurae is related to the sockeye salmon, Oncorhynchus nerka, and has been earlier treated as its subspecies O. nerka kawamurae. The fish was thought to have gone extinct in 1940 when a hydroelectric project made Lake Tazawa, its native lake, more acidic. Prior to that, 100,000 eggs were transferred to Lake Saiko, which is located about 310 miles (500 kilometers) south of Lake Tazawa, but this attempt to save the fish was thought to have been unsuccessful. However, in 2010, a team of researchers found living members of the species in Saiko Lake.^[1]

The fish is dark olive with black spots on its back, and grows to approximately one foot (30 centimeters) in length.^[1]

References

• ´Froese, Rainer, and Daniel Pauly, eds. (2012). "Oncorhynchus kawamurae" in FishBase. April 2012 version.

Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos ("hook") and rynchos ("nose"), in reference to the hooked jaws of males in the mating season (the "kype").

Range

Salmon and trout with ranges generally in waters draining to the Pacific Ocean are members of the genus. Their range extends from Beringia southwards, roughly to Japan in the west and Mexico to the east. In North America, some subspecies of O. clarki are native to the landlocked Great Basin, while others are native to the Rio Grande and western tributaries of the Mississippi River Basin which drain to the Gulf of Mexico, rather than to the Pacific.

Unlike many trout species of the mainly European genus Salmo, many Oncorhynchus are anadromous (migratory) and semelparous (die after spawning). Some species of char (Salvelinus genus) are native to Pacific waters and are also referred to as trout.

Evolution

Several late Miocene (~7 m.y.a.) trout-like fossils appear in Idaho, in the Clarkia Lake beds appear to be Oncorhynchus—the current genus for Pacific salmon and some trout.^[1] The presence of these species so far inland established that Oncorhynchus was not only present in the Pacific drainages before the beginning of the Pliocene (~5–6 m.y.a.), but also that rainbow 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. Suggestions have gone back as far as the early Miocene (~20 m.y.a.).^[2][3] One fossil species assigned to this genus is Oncorhynchus rastrosus, the Sabertooth salmon (sometimes called Smilodonichthys), a 9-foot-(3 meter-)long species known from Late Miocene to Pleistocene fossil.^[4]

Speciation among Oncorhynchus has been examined for decades, and to this day, a family "tree" is not 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. It is generally agreed that chum, pink and sockeye salmon lineages diverged in the sequence after other species.^[2] Montgomery (2000) discusses the pattern of the fossil record as compared to tectonic shifts in the plates of the Pacific Northwest America. The (potential) divergence in Onchorhyncus 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.^[3]

One interesting case involving speciation with salmon is that of the Kokanee, sockeye that have been landlocked. 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 appears that it does apply only to sympatry, and this limitation makes the definition difficult to apply. There are examples in Washington, Canada and elsewhere where two populations live in the same lake but spawn in different substrates, at different times, and eat different food sources.^[5] 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.

Species

Some of the species in this genus are highly variable and there has been a plethora of taxa described that have not withstood the test of time. The following list follows the most recent treatment in Fishbase. There are currently 15 recognized species in this genus: ^[6]

• Oncorhynchus aguabonita (D. S. Jordan, 1892) (Golden trout)
• Oncorhynchus apache (R. R. Miller, 1972) (Apache trout, Arizona trout)
• Oncorhynchus chrysogaster (Needham & Gard, 1964) (Mexican golden trout)
• Oncorhynchus clarkii (J. Richardson, 1836) (Cutthroat trout)
  • Oncorhynchus clarkii clarkii (J. Richardson, 1836) (Coastal cutthroat trout, Yellowstone cutthroat trout, Westslope cutthroat trout)
  • Oncorhynchus clarkii pleuriticus (Cope, 1872) (Colorado River cutthroat trout)
• Oncorhynchus gilae (R. R. Miller, 1950) (Gila trout)
• Oncorhynchus gorbuscha (Walbaum, 1792) (Pink salmon, Humpback salmon)
• Oncorhynchus iwame Seiro Kimura & M. Nakamura, 1961 (Iwame trout, Markless trout)
• Oncorhynchus kawamurae D. S. Jordan & E. A. McGregor, 1925 (Kunimasu, Black kokanee)
• Oncorhynchus keta (Walbaum, 1792) (Chum salmon, Dog salmon, Keta salmon, Silverbrite salmon)
• Oncorhynchus kisutch (Walbaum, 1792) (Coho salmon, Silver salmon, silvers)
• Oncorhynchus masou (Brevoort, 1856) (Seema, Masu salmon, Cherry salmon, Japanese salmon)
  • Oncorhynchus masou formosanus (D. S. Jordan & Ōshima, 1919) (Taiwanese salmon, Formosan landlocked salmon)
  • Oncorhynchus masou macrostomus (Günther, 1877) (Amago, Red-spotted masu salmon)
  • Oncorhynchus masou masou (Brevoort, 1856) (Masu Salmon, Seema, Yamame, Satsukimasu salmon)
• Oncorhynchus mykiss (Walbaum, 1792) (Rainbow trout, Steelhead, Ocean trout, Columbia River redband trout)
• Oncorhynchus nerka (Walbaum, 1792) (Sockeye salmon, Red salmon, Blueback salmon, Kokanee)
• Oncorhynchus rhodurus D. S. Jordan & E. A. McGregor, 1925 (Biwa trout)
• Oncorhynchus tshawytscha (Walbaum, 1792) (Chinook salmon, Blackmouth, Black salmon, Chub salmon, Columbia River salmon, Hookbill salmon, King salmon, Quinnat salmon, Spring salmon, Tyee salmon, Winter salmon)

In addition to the above, the following taxa and varieties have been named:

• Oncorhynchus clarkii
  • Oncorhynchus clarkii alvordensis – Alvord cutthroat trout (extinct)
  • Oncorhynchus clarkii behnkei – Snake River fine-spotted cutthroat trout
  • Oncorhynchus clarkii clarkii f. crescentii – Lake Crescent cutthroat trout, Crescenti trout (sometimes O. c. crescentii)
  • Oncorhynchus clarkii henshawi – Lahontan cutthroat trout
  • Oncorhynchus clarkii macdonaldi – Yellowfin cutthroat trout (extinct)
  • Oncorhynchus clarkii seleniris – Paiute cutthroat trout
  • Oncorhynchus clarkii stomias – Greenback cutthroat trout
  • Oncorhynchus clarkii utah – Bonneville cutthroat trout
  • Oncorhynchus clarkii virginalis – Rio Grande cutthroat trout
• Oncorhynchus mykiss
  • Oncorhynchus mykiss irideus f. beardsleei – Beardslee trout, (sometimes O. m. beardsleei)
  • Oncorhynchus mykiss newberrii – Great Basin redband trout

Footnotes

References

• Behnke, Robert J. (2002): Trout and Salmon of North America. Free Press, 2002.
• Sepkoski, Jack (2002): Osteichthyes. In: A compendium of fossil marine animal genera. Bulletin of American Paleontology 364: 560. HTML fulltext
• Stearley, R.F. & Smoth, G.R. (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. DOI:10.1577/1548-8659(1993)122<0001:POTPTA>2.3.CO;2 HTML fulltext
• Stephenson, S.A. (2005) The distribution of Pacific salmon (Oncorhynchus spp.) in the Canadian western Arctic. http://www.dfo-mpo.gc.ca/Library/321160.pdf

The golden trout (Oncorhynchus aguabonita) is a species of trout considered by many to be a sub-species of the rainbow trout It closely resembles the juvenile Rainbow trout. The fish is also known as the California golden trout and is native to Golden Trout Creek, Volcano Creek and the South Fork Kern River. Another variant, O. m. whitei, was historically found only in the Little Kern River but is now found in other nearby creeks, as well. The golden trout is commonly found at elevations of 10,000 ft (3,000 m) above sea level, and is native to California. Originally placed in the species Oncorhynchus aguabonita, most taxonomists now classify the golden trout as a subspecies of the rainbow trout, Oncorhynchus mykiss,^[1][2] placing it with several other subspecies commonly known as redband trout, Oncorhynchus mykiss ssp.

Photo of Golden Trout from within the John Muir Wilderness.

Golden Trout caught in high mountain lake of the Wind River Range.

The golden trout has golden flanks with red, horizontal bands along the lateral lines on each side and about 10 dark, vertical, oval marks (called "parr marks") on each side. Dorsal, lateral and anal fins have white leading edges. In their native habitat, adults range from 6–12 in (15–30 cm) long. Fish over 10 in (25 cm) are considered large. Golden trout that have been transplanted to lakes have been recorded up to 11 lb (5 kg) in weight. The world record golden trout was caught by Charles S. Reed, on August 5, 1948, from Cook Lake in the Wind River Range. That fish was 28 in (70 cm) long and weighed 11.25 lb (5.1 kg).^[3] Preferred water temperature is 58–62 °F (14–17 °C).^{[citation needed]}

Years of overexploitation, mismanagement and competition with exotic species have brought these fish to the brink of being designated as threatened. Introduced brook trout (Salvelinus fontinalis) outcompete them for food, introduced brown trout (Salmo trutta) prey on them and introduced rainbow trout (O. mykiss) hybridize with them, damaging the native gene pool through introgression.

The golden trout was designated the state fish of California in 1947. Populations have been in steady decline for decades. As a result, the California Department of Fish and Game signed an agreement with federal agencies in September 2004 to work on restoring back-country habitat. Conservationists have also been attempting to introduce golden trout to other waters such as to Lake Mohave in Nevada and Arizona.

The golden trout should be distinguished from the similarly named golden rainbow trout, also known as the palomino trout. The golden rainbow is actually a color variant of the rainbow trout.^[4]

Chuck Yeager and the New Mexico population

Colonel Chuck Yeager introduced one of his commanding officers, General Irving "Twig" Branch, to the Sierra Nevada populations of golden trout, Branch ordered Yeager and Bud Anderson to introduce the species to the mountain streams of New Mexico, where they can be fished to this day.^[5]

In his second autobiography, Press On, Yeager details his annual fishing trips to catch golden trout which he extols as one of the best game fish and best eating fish to be found.

References

Crescenti cutthroat trout (a hypercorrection) or Lake Crescent cutthroat trout (a more literal translation of the scientific name Oncorhynchus clarki clarki f. crescentii) is a local form (f. loc.) of Coastal cutthroat trout isolated in Lake Crescent in Washington and is not currently recognized as an official subspecies (Behnke 1992). However the cutthroat trout of Lake Crescent do remain distinct, with the highest known gill raker and vertebrae counts of any coastal cutthroat population. The cutthroat are believed to have been isolated in Lake Crescent after a landslide blocked the eastern outflow of the lake.

Before the introduction of non-native trout to the lake, these fish co-existed with the lake's population of coastal rainbow trout known as Beardslee trout. The cutthroat mostly used the lake's inlet stream Barnes Creek for spawning, while the rainbow trout used the Lyre River for spawning. However in the early 1980s a small cutthroat population was found in the Lyre River that spawns further downstream than the native rainbow trout. Today the cutthroat of Barnes Creek have been hybridized with introduced rainbow into cutbows, but Crescenti cutthroat trout persist in the Lyre River as a genetically pure population (Behnke 1992). A Crescenti cutthroat caught in 1961 set the state record for cutthroats at 32 inches (81 cm) and 12 pounds (5.4 kg).^[1][2]

References

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