Today, remnant native populations in the Big Hole River and Red Rock River drainages represent approximately four percent of the subspecies’ historical range.[3]
Taxonomy
The scientific name of the Montana Arctic grayling, when treated as a subspecies, is Thymallus arcticus montanus. It was first described in 1874 as Thymallus montanus by American fisheries biologist James W. Milner.[10]
In modern taxonomy, North American fisheries and conservation authorities generally classify the Montana grayling not as a distinct subspecies but as a distinct population segment of the Arctic grayling (Thymallus arcticus).[9][3][11]
Description
The Montana Arctic grayling is distinguished by its large, sail-like dorsal fin and vivid coloration. The dorsal fin is typically edged in red and marked with iridescent red, aqua, or purple spots, which are most pronounced in larger individuals. The back is generally dark, while the sides vary in color from silver and gold to bluish tones. A band of gold often separates the flanks from the white underside. The pelvic fins are streaked with iridescent orange, red, or pink, providing a striking contrast to the pale belly. The body and head may be sprinkled with small black spots, and a dark slash is usually visible along each side of the lower jaw. The iris is often golden in hue. In contrast, the adipose, caudal (tail), pectoral, and anal fins tend to be dull gray and less colorful.
Range
Native and introduced range of Arctic grayling, Thymallus arcticus, in the United States.
The historic native range of the fluvial (river-dwelling) form of the Montana Arctic grayling encompassed the mainstem and tributaries of the upper Missouri River as far downstream as the Great Falls. This range was isolated from northern populations of the Arctic grayling in Canada following the last glaciation and from the southern populations in Montana and Michigan. The Michigan grayling (T. a. tricolor) is now extinct.[13]
During the 1804–1806 Lewis and Clark Expedition, the explorers did not encounter grayling until they reached the Beaverhead River, a secondary tributary of the Missouri. They described the fish as “white trout.”[13] In 1915, U.S. Bureau of Fisheries biologist W. C. Kendall described the Montana grayling as “abundant” in the Madison River, Firehole River, and Gibbon River within Yellowstone National Park.[14] These headwaters of the Missouri River represent the southern extent of the grayling’s historical range in Wyoming.
The introduction of non-native brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss) into the upper Missouri River basin beginning in the 1890s caused a sharp decline in fluvial grayling populations and range. In Howard Back’s 1938 work, The Waters of Yellowstone with Rod and Fly, he lamented that he was unable to find any grayling in the Madison River.[15] By the 1950s, the only grayling in the park were lacustrine (lake-dwelling) forms introduced into Grebe Lake.[16]
The native range of the adfluvial (lake-migrating) form was restricted to the Red Rock Lakes at the headwaters of the Beaverhead River and several small mountain lakes in the Big Hole River drainage.
The current range of the fluvial Montana grayling is limited to approximately 80 miles (130km) of the Big Hole River between Melrose, Wisdom, and Jackson. The highest concentrations occur near Wisdom.[17] This represents roughly four percent of the species’ original native range.
In the early 20th century, fisheries agencies began introducing Arctic grayling into suitable lake environments across Montana. Most of these introductions used fluvial stocks originating from Montana, though some came from Arctic grayling populations in Alaska and Canada.
Grayling in Grebe Lake, Yellowstone National Park (2009)
In 1921, U.S. Fish Commission personnel stocked Grebe Lake—then fishless—with a lacustrine form of the Montana Arctic grayling. The original stock came from Georgetown Lake near Anaconda. Between 1931 and 1956, over 72 million grayling eggs were harvested from Grebe Lake and distributed to hatcheries throughout the western United States. Most lake-dwelling grayling populations in the region today can be genetically traced to these Grebe Lake stocks.[16][18] Grebe Lake was closed to fishing until 1944 due to ongoing fish culture operations.
Life cycle
Fluvial Montana grayling spend their entire life cycle in riverine environments. They make seasonal migrations within river systems for spawning, feeding, and overwintering, with migrations of up to 50 miles (80km) documented. Grayling inhabit cold freestone streams with low to moderate gradients. Adult fluvial grayling prefer deep pool habitats.
In Montana, grayling spawn from late April to mid-May, depositing adhesive eggs over sand and gravel substrates without excavating a redd. Eggs hatch within several weeks. Juvenile grayling are weak swimmers and typically occupy stream margins that provide velocity refuges—such as backwaters, side channels, and areas near beaver dams. Grayling in Montana generally reach sexual maturity in their third or fourth year and rarely live beyond six years.
Grayling of all ages are opportunistic feeders. Their diet includes larval, pupal, and adult stages of aquatic insects—particularly caddisflies, stoneflies, mayflies, and aquatic dipterans. They also consume terrestrial insects, such as ants, beetles, grasshoppers, and crickets, that fall into the water. Other prey items include crayfish, shrimp, and other small crustaceans. The species’ aggressive feeding behavior is associated with its habitat preferences: grayling often occupy deep pools with little large woody debris, allowing efficient visual foraging.
Adfluvial forms of the Montana grayling spend most of the year feeding and overwintering in lakes, migrating into suitable tributary streams to spawn.
In March 2006, the U.S. Fish and Wildlife Service (USFWS) established a Candidate Conservation Agreement with Assurances (CCAA) between the agency and several non-federal entities. Under such agreements, non-federal property owners who voluntarily manage their lands or waters to reduce threats to species at risk of becoming threatened or endangered receive assurances that no additional regulatory requirements will be imposed if the species is later listed under the Endangered Species Act (ESA).
The goal of this agreement was to conserve and enhance populations of fluvial Arctic grayling (Thymallus arcticus) within the upper portion of their historic range in the Big Hole River drainage.[19]
On August 19, 2014, the U.S. Fish and Wildlife Service (USFWS) announced that, following years of status reviews and conservation efforts, the Montana population of fluvial Arctic grayling (Thymallus arcticus) did not warrant listing under the Endangered Species Act (ESA). The decision was based on evidence that existing conservation measures and partnerships were effectively addressing threats to the species.[20]
The finding reflected decades of cooperative conservation beginning in the early 1990s through initiatives such as the Arctic Grayling Recovery Program and the Big Hole Watershed Committee, and was further supported by the Candidate Conservation Agreement with Assurances (CCAA) for fluvial Arctic grayling. Over more than two decades, ranchers, conservation organizations, government agencies, and local stakeholders collaborated to improve habitat conditions and stream flows in the Big Hole River drainage. The Arctic grayling were also a central focus in the formation of the Big Hole Watershed Committee in 1995, which continues to promote sustainable water management and habitat restoration in the region.
Reintroduction efforts
A Montana fluvial Arctic grayling broodstock program was established to preserve the genetic integrity of the state’s fluvial grayling populations and to supply fish for reintroduction efforts. Three fluvial broodstock sources are maintained at the Yellowstone River Trout Hatchery, the Axolotl Chain of Lakes, and the Green Hollow II Reservoir. Reintroduction efforts began in 1997 in the upper Ruby River and expanded to the North and South forks of the Sun River and the lower Beaverhead River in 1999, as well as the Missouri River headwaters near Three Forks, Montana in 2000.
Since 2002, reintroduction activities have primarily focused on the upper Ruby River. In 2008, additional efforts took place in the upper Ruby River and the North Fork of the Sun River, where remote site incubators were used to introduce grayling fry into designated restoration reaches.[21]
An environmental DNA (eDNA) assay using 5 litres (1.3USgal) of stream water was later developed to detect Arctic grayling with high specificity, distinguishing them from other native and non-native salmonids in Montana.[22]
↑ Milner, J. W. (1874). "Notes on the grayling of North America." United States Commission of Fish and Fisheries, Report of the Commissioner, Part 2 (for 1872–73): 729–742.
↑ "Montana Field Guide – Arctic Grayling (Thymallus arcticus)". Montana Natural Heritage Program and Montana Fish, Wildlife & Parks. Retrieved 13 March 2014. Species of Concern are native taxa that are at risk due to declining population trends, threats to their habitats, restricted distribution, and/or other factors. Designation is not statutory or regulatory but helps guide conservation priorities.
↑ Milner, James W. (1874). "Notes on the Grayling of North America"(PDF). Report of the Commissioner of Fish and Fisheries (1872–1873), Chapter XXX. United States Commission of Fish and Fisheries. pp.729–742. Retrieved 13 March 2014.
1 2 Behnke, Robert J.; Tomelleri, Joseph R. (2002). "Arctic Grayling Thymallus arcticus". Trout and Salmon of North America. The Free Press. pp.327–331. ISBN0-7432-2220-2.
↑ Schullery, Paul; Varley, John D. (1998). Yellowstone Fishes: Ecology, History, and Angling in the Park. Mechanicsburg, PA: Stackpole Books. ISBN0-8117-2777-7.
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