What are Arctic Grayling?

The Arctic grayling is a species native to northern North America. The only populations native to the lower 48 states were in Michigan and Montana, and the Michigan population is now extinct. Consequently, the fluvial or river-dwelling population in the upper Big Hole River are the last remnants of this native fish. Originally, the fluvial Arctic grayling was widespread throughout the upper Missouri river drainage as far downstream as Great Falls. Lewis and Clark made note of these "new kind of white or silvery trout" in 1805. The lake-dwelling form is fairly common in 30 or more lakes across the western half of the state. These lake fish are genetically, but not visibly, different from our native fluvial grayling. Grayling are gullible to the angler's lures and also seem to be easily out-competed by other salmonid species. This probably explains much of their demise from their native range. They are spring spawners and broadcast their eggs over a gravel bottom in moving streams. Grayling can overpopulate, producing severely stunted populations in some mountain lakes. Grayling are truly a unique Montana species. The iridescent hues of a spawning grayling's dorsal fin are brilliant. Exceptional individuals can weigh up to 3 pounds and reach 20 inches in length. They are generalists, eating a variety of aquatic invertebrates (FWP).

Where do Arctic Grayling Live?

Today in Montana Arctic grayling are found primarily small, cold, clear lakes with tributaries suitable for spawning. They do not coexist well with other fishes except cutthroat trout and others with which they evolved.

At the end of the 19th Century, fluvial Arctic grayling were intermittently distributed throughout the upper Missouri drainage above Great Falls (Vincent 1962). During the 20th Century, the range of fluvial Arctic grayling has been restricted to the Big Hole River of southwest Montana, about 4% of its native range (Kaya 1992a). Vincent (1962) attributed the decline of fluvial Arctic grayling throughout their native range to four factors: habitat degradation, introduction of non-native salmonids, climatic change, and exploitation by anglers (AFS website 2003).

Are There Any Threats or Limiting Factors to Arctic Grayling?

Factors potentially threatening survival of Arctic grayling in the Big Hole River include water quality and quantity, competition with introduced species, predation, habitat degradation, and impacts of angling. Water quantity issues include drought and recruitment limitation due to sudden runoff events. Sudden increases in stream flows during hatching and emergence of larval Arctic grayling may decrease survival and limit recruitment in the Big Hole River (Shepard and Oswald 1989). Oswald (personal communication) hypothesized that extreme flood flows severely impacted Arctic grayling recruitment in the Big Hole River during 1984 and 1985 (AFS website 2003).

Conversely, extreme low flows during severe drought decrease survival of older Arctic grayling due to high water temperatures, increased susceptibility to predation, and diminished habitat volume. The distribution of Arctic grayling in the Big Hole basin suggests that they are displaced by non-native brown and rainbow trout. Recent studies indicate overlap in microhabitat preferences between Arctic grayling and rainbow trout (Magee and Byorth 1995). Predation on juvenile Arctic grayling by all non-native species is also a potential limiting factor (Kaya 1992a) (AFS website 2003).

The Big Hole River fluvial population is small enough that stochastic environmental perturbations could result in extinction (Gilpin 1996). Harvest of grayling is prohibited but incidental kill probably still occurs. Probably exotic fish are not increasing in the Big Hole River; the habitat may or may not be getting worse (Gilpin 1996). In all three native populations, irrigation diversions are present which may block movement, dewater streams, elevate temperatures, and increase silt loads (Gilpin 1996, Mogen 1996). In the Red Rock Lakes area the population is faced with high siltation in breeding streams and deposition in the lakes; the lakes are drastically reduced in depth with high temperatures in the summer and freezing to the bottom in winter (Mogen 1996). Cattle grazing is contributing greatly to this situation. Dams are barriers to movement and perhaps increase sediment deposition in artifically raised lakes or reservoirs.

Information courtesy of Montana Fish, Wildlife, and Parks