Arctic grayling

Arctic Grayling
T. arcticus arcticus
Conservation status
Secure
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Salmoniformes Family: Salmonidae Subfamily: Thymallinae Genus: Thymallus Species: T. arcticus
Binomial name
Thymallus arcticus (Pallas, 1776)

The Arctic grayling (Thymallus arcticus) is a species of freshwater fish in the salmon family (family Salmonidae) of order Salmoniformes. It comprises five subspecies.

The species is native to the Nearctic and Palearctic ecozones. T. a. arcticus is widespread throughout the Arctic and Pacific drainages in Canada, Alaska, and Siberia, as well as the upper Missouri River drainage in Montana. The other subspecies have narrower ranges. T. a. baicalensis is restricted to the Lake Baikal drainage in Russia. T. a. grubii is found only in the Amur basin in east Asia.

Several life history forms of Arctic grayling occur: fluvial populations that live and spawn in rivers; lacustrine populations that live and spawn in lakes; and potamodromous populations that live in lakes and spawn in tributary streams.

The upper Missouri River basin population once merited a high priority for Endangered Species Act (ESA) listing by the US Fish & Wildlife Service (FWS). This unique southernmost population is now extirpated from all areas of the basin with the exception of the Big Hole River watershed. In preparation for an ESA listing, the US FWS began implementing a "Candidate Conservation Agreement with Assurances" (CCAA). This agreement would protect cooperating landowners from being prosecuted under the ESA "takings" clause so long as they fulfil specific obligations, spelled out in a contractual arrangement and intended to restore the dwindling population. The CCAA , however, is now in doubt. On 25 April 2007, the FWS removed Big Hole River grayling from ESA candidacy based on arguments that (1) the rarer fluvial populations should not have been "lumped together" with the more common lake-dwelling populations and (2) the Montana grayling populations are insignificant and their loss would be inconsequential given the presence of thriving populations in Alaska. See Montana Grayling Genetics.

T. a. arcticus grows to a maximum recorded length of 76 cm (30 inches) and a maximum recorded weight of 3.8 kg (8.4 pounds); the other subspecies range in maximum length from 30 to 44 cm (12 to 17 inches), with maximum weights of about 1 to 1.3 kg (2 to 3 pounds). Of typical thymalline appearance, the Arctic grayling is distinguished from the similar grayling (T. thymallus) by the absence of dorsal and anal spines and by the presence of a larger number of soft rays in these fins. There is a dark midlateral band between the pectoral and pelvic fins, and the flanks may possess a pink iridescence. Some subspecies exhibit distinctive coloration. T. a. baicalensis is darker in colour with two wide vertical bars of lighter shade along its body. T. a. arcticus has been recorded as reaching an age of 18 years.

The Arctic grayling occurs primarily in cold waters of mid-sized to large rivers and lakes, returning to rocky streams to breed, although T. a. baicalensis remains in shallow waters for its entire life. The various subspecies are omnivorous. Crustaceans, insects and insect larvae, and fish eggs form the most important food items. Larger specimens of T. a. arcticus become piscivorous and may even take small aquatic mammals, such as lemmings. The immature fish feed on zooplankton and insect larvae.

10" Arctic Grayling from the Gulkana River, Paxson, Alaska.

Spawning takes place in the spring. Adult fish seek shallow areas of rivers with fine, sand substrate and moderate current. Males are territorial and court females by flashing their colourful dorsal fins; the fins are also used to brace receptive females during the vibratory release of milt and roe. The fish are nonguarders: the eggs are left to mix with the substrate. Although the Arctic grayling does not excavate a nest, the highly energetic courtship and mating tends to kick up fine material which covers the zygotes. The zygote is small (approximately 3 mm in diameter) and the embryo will hatch after two to three weeks. The newly-hatched embryo remains in the substrate until all the yolk has been absorbed. They emerge at a length of around 12 to 18 mm (0.5 to 0.7 inches), at which time they form shoals at the river margins. The juveniles grow quickly during their first two years of life.

As is the grayling (T. thymallus), the Arctic grayling is economically important, being raised commercially for food and fished for sport.

The species is sensitive to pollution and, although it has been extirpated from portions of its range, it remains widespread elsewhere and hence is not listed on the IUCN Red List of threatened species.

Obsolete synonyms for T. a. arcticus include T. montanus, T. signifer, and T. tricolor. The species is also known as the Alaska grayling.

Several submarines and patrol boats of the United States Navy have been named USS Grayling after this species.

Subspecies

• Thymallus arcticus arcticus (Pallas, 1776) – Arctic grayling
• T. a. baicalensis (Dybowski, 1874) – Baikal black grayling
• T. a. grubii Dybowski, 1869 – Amur grayling
• T. a. mertensii Valenciennes, 1848
• T. a. pallasi Valenciennes, 1848 – East Siberian grayling

T. yaluensis is sometimes also listed as a subspecies of T. arcticus but it may be identical to T. a. grubii.

References

• "Thymallus arcticus arcticus". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
• "Thymallus arcticus baicalensis". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
• "Thymallus arcticus grubii". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
• "Thymallus arcticus mertensii". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
• "Thymallus arcticus pallasi". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
• Thymallus arcticus (TSN 162016). Integrated Taxonomic Information System. Accessed on 11 December 2004.
• FWS (2004). U.S. Fish and Wildlife Service Species Assessment and Listing Priority Assignment Form for fluvial Arctic grayling (distinct population segment of the Upper Missouri River), commonly called Montana Arctic grayling. November 30, 2004.

External Links

• EcoRover blog about Big Hole River grayling
• Pat Munday's rating of Big Hole Watershed Committee effectivness in Big Hole River grayling restoration
• Length and age at maturity of Arctic grayling in the Snake River during 2003 / by Alfred L. DeCicco and Andrew D. Gryska. Hosted by Alaska State Publications Program.
• Summer abundance of Arctic grayling in the Chena River, 2005 by Klaus G Wuttig; Steven M Stroka; Alaska. Division of Sport Fish.; Alaska. Division of Commercial Fisheries. Hosted by Alaska State Publications Program.

Donate to Wikimedia