Dolly Varden Trout

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Dolly Varden Trout
female

female

Systematics
Overcohort : Clupeocephala
Cohort : Euteleosteomorpha
Order : Salmonid fish (Salmoniformes)
Family : Salmon fish (Salmonidae)
Genre : Char ( salvelinus )
Type : Dolly Varden Trout
Scientific name
Salvelinus malma
( Walbaum , 1792)

The dolly varden trout ( Salvelinus malma ) is a species of char from the salmon fish family .

features

It is a medium-sized salmonid with an average body length of 36 to 46 centimeters and a body weight of 0.45 to 1.1 kilograms. Under unfavorable conditions, such as in small streams, it only reaches 10 to 13 centimeters and weighs around 28 grams. The previous record reached 8.7 kilograms. They typically reach fertility with a body length of 12 to 21 centimeters. With 220 to 300 rows on each side of the body, the scaling is even smaller than that of most salmonids, so that the fish appear scaly when viewed from a distance. The coloring is extremely variable. As char, it can be distinguished from species of the genera Salmo and Oncorhynchus in that the flanks have light (whitish to pink) spots on a darker background, not dark spots on a lighter background. Animals living in the sea are mostly silvery with a green shimmer with orange spots, whereas those living in fresh water tend to be brown to green, with orange to red spots. At spawning time, males develop a splendid coloration with a green-black back with bright red spots, a red belly, black gill covers and orange and black colored fins with a white border. Like many salmonids, the males then form an upwardly curved mouth hook.

The species is difficult to distinguish with certainty from other species of char, of which about five species live in North America (depending on the conception and species delimitation); In particular, bull trout and arctic char can become extremely similar. The shape and color characteristics are very variable within the species and overlap with those of related species; there are also hybrids where the distribution areas overlap or where species have been exposed outside of their natural range. An exact determination is only possible on the basis of internal characteristics and in many cases remains uncertain; it is then only possible using genetic markers. The ploughshare (vomer) only has teeth in the front section (generic feature). The gill pots have 16 to 19 teeth in southern animals and 20 to 24 teeth in those in the north. The number of vertebrae is between 62 and 70. The number of pyloric tubes in the stomach is between 25 and 30, both significantly fewer than in (North American) arctic char. The distinction from the bull trout in areas with sympatric distribution is only possible externally with larger, typical specimens. Large bull trout have larger heads and jaws, the head is more flattened on top; the eyes are a little higher on the head. Important characteristics for the exact differentiation from the bull trout are the number of gill rays, the rays of the anal fin and the ratio of the maxillary length to the total length; Since these values ​​are allometrically related to body size, they have to be calculated morphometrically using a complex formula . Even then, there remain individuals who cannot be determined or are assigned to the wrong species.

distribution

Spawning waters of the species are flowing waters that flow into the northeast Pacific on both sides of the Bering Strait and the adjacent Arctic Ocean , and more rarely stagnant waters such as lakes. They live near the sea on the west coast of North America, south to Puget Sound in Washington , over British Columbia , Yukon and large parts of Alaska to the Northwest Territories and east to the Mackenzie River . In Asia, northeast Siberia is populated west to Kolyma including the offshore islands and Kamchatka , south to the Japanese island of Hokkaidō . Common (sympatric) occurrences with the closely related and similar bull trout only exist in a strip in western British Columbia and in the subsequent northern Washington.

Biology, habitat and way of life

The species mostly lives as an anadromous migratory fish ; This means that young animals migrate through rivers to the sea, but mating and spawning always take place in fresh water. In addition to anadromous populations, there are also more rarely, especially in the south of the range, populations in lakes isolated from the sea that do not migrate. The fish overwinter in fresh water, and animals migrate from small bodies of water to large lakes or rivers. Sexual maturity is reached in Alaska at 5 to 6 years, the southern subspecies reaches an age of about 8, the northern subspecies up to 16 years. They can spawn (up to three times) over a period of several years. The mating and spawning season is in autumn. The females lay 600 to 6,000, in the north up to 10,000 eggs in the gravel bottom of the water. In the second to fourth year of life, the fry of anadromous populations migrate into the sea.

The species is relatively unspecialized in its diet.

Taxonomy and systematics

The division of the genus Salvelinus into species is a difficult problem on which there is still no consensus. After all of the "myriads of described and undescribed forms" had been combined in one species ( Salvelinus alpinus ) until further clarification , the view prevailed in the 1960s that two species, Salvelinus alpinus and Salvelinus malma , would exist. In 1978, Ohio State University's Ted Cavender stated that what had previously been considered salvelinus malma must in fact be two species, and that the bull trout ( salvelinus confluentus ) is specifically different from the dolly varden. It is therefore unclear which type of information is actually related to all older statements.

Further advances were then achieved primarily through the new discipline of phylogenomics, in which the comparison of homologous DNA sequences is used as a working tool in phylogeny and systematics. At the same time, the Asian populations of the species complex were again examined more intensively; the type Salvelinus malma was originally by Johann Julius Walbaum 1792 on the basis of animals from Siberia (as Salmo malma ) firstdescribed Service. Initially, a northern and a southern population could be distinguished both in Asia and in America. The analysis turned out to be difficult, however, because the species are evidently evolutionarily young (a few million years old) and in some cases have been influenced by introgression as a result of hybridization events, which means that pedigrees based on MtDNA and nuclear DNA do not always match.

The southern Asian population, initially regarded as the subspecies Salvelinus malma krascheninnikovi Taranetz , was later elevated to the rank of species as Salvelinus curilus ( Pallas , 1814). The northern Asian and American populations were found to be genetically and morphologically identical. According to this, two subspecies are often distinguished today (which are not accepted by all taxonomists):

  • Salvelinus malma malma ( nominate form , northern subspecies) - Northeast Asia, northwestern North America
  • Salvelinus malma lordii ( Günther , 1866), also written as lordi (southern subspecies) - North America, south of the Gulf of Alaska

Naming

Dolly Varden is a character in Charles Dickens ' novel Barnaby Rudge with a penchant for very colorful clothes. In the 19th century, when history was far more popular than it is today, very colored clothes were generally given this name more often. Anglers transferred it to the very colorful fish (in their spawning dress) that they caught in rivers in North America.

Frequency, economic importance

The species is not rare in parts of its range.

In the first half of the 20th century, Dolly Varden were persecuted as " pests ". The species was rather unpopular with anglers at the time, and it was assumed that it would harm the offspring of popular food fish such as Pacific salmon species . From 1921 to 1940, the US Fisheries Agency even paid a premium for tail fins of the species that were delivered. Today we know that the assumption was completely unfounded; the dolly-varden trout may even indirectly promote the salmon offspring. Today the species is fished intensively by sport anglers and has therefore become rare in parts of its range. Therefore, catch restrictions apply in parts of Alaska. In some cases, stocks are also being decimated by bycatch in commercial salmon fisheries.

Individual evidence

  1. ^ A b c d Robert Behnke: Trout an Salmon of North America. Simon and Schuster, 2010. 384 pp. ISBN 978-1-4516-0355-2
  2. ^ Salvelinus malma at Fishbase.org
  3. ^ JD McPhail: The Freshwater Fishes of British Columbia. University of Alberta Press, 2007. ISBN 978-0-88864-853-2 , p. 333.
  4. a b James S. Baxter, Eric B. Taylor, Robert H. Devlin, John Hagen, J. Donald McPhail (1997): Evidence for natural hybridization between Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluentus) in a northcentral British Columbia watershed. Canadian Journal of Fisheries and Aquatic Sciences 54: 421-429.
  5. Jason Dunham, Colden Baxter, Kurt Fausch, Wade Fredenberg, Satoshi Kitano, Itsuro Koizumi, Kentaro Morita, Tomoyuki Nakamura, Bruce Rieman, Ksenia Savvaitova, Jack Stanford, Eric Taylor, Shoichiro Yamamoto (2008): Evolution, Ecology, and Conservation of Dolly Varden, White-spotted Char, and Bull Trout. Fisheries vol 33 no 11: 537-550.
  6. ^ A b c Robert H. Armstrong and Marge Hermans: Dolly Varden (Salvelinus malma), Chapter 8.8 in John W. Schoen and Erin Dovichin (editors): The Coastal Forests and Mountains Ecoregion of Southeastern Alaska and the Tongass National Forest A conservation assessment and resource synthesis. March 2008.
  7. ^ Alaska Department of Fish and Game: Dolly Varden species profile
  8. ^ V. Walters (1955): Fishes of Western Arctic America and Eastern Arctic Siberia. Bulletin of the American Museum of Natural History 106, 368 pp.
  9. JD McPhail (1961): A Systematic Study of the Salvelinus alpinus Complex in North America. Journal of the Fisheries Research Board of Canada 18 (5): 793-816.
  10. ^ TM Cavender (1978): Taxonomy and distribution of the bull trout, Salvelinus confluentus (Suckley) from the American Northwest. California Fish and Game 64: 139-174.
  11. AG Oleinik, LA Skurikhina, Vl.A. Brykov, PA Crane, JK Wenburg (2005): Differentiation of Dolly Varden Char Salvelinus malma from Asia and North America Inferred from PCR-RFLP Analysis of Mitochondrial DNA. Russian Journal of Genetics Vol. 41, No. 5: 501-508. (Translated from Genetika Vol. 41, No. 5: 626-634.)
  12. SV Shedko, IL Miroshnichenko, GA Nemkova (2013): Phylogeny of Salmonids (Salmoniformes: Salmonidae) and its Molecular Dating: Analysis of mtDNA Data. Russian Journal of Genetics Vol. 49, No. 6: 623-637. (Translated from Genetika Vol. 49, No. 6: 718-734.)
  13. EA Salmenkova & VT Omelchenko (2013): Genetic divergence and taxonomic status of chars of the genus Salvelinus. Biology Bulletin Reviews 3 (6): 481-492.
  14. Salvelinus curilus at Fishbase.org
  15. Salmo lordii at WoRMS World Register of Marine Species

Web links

Commons : Dolly Varden Trout ( Salvelinus malma )  - Collection of images, videos and audio files