Montana Arctic Grayling

Thymallus arcticus

The Arctic grayling Thymallus arcticus ranges in distribution from northern Asia to northern North America, but within the lower 48 United States the Arctic grayling only occurred historically in Michigan and in Montana. The Arctic grayling was historically found in Otter Creek (Upper Peninsula) and Jordan River (Lower Peninsula) in Michigan but is now extinct (circa 1936). Historical accounts showed grayling to formerly occur in the Sun River, Smith River, Gallatin River, Madison River, Red Rock-Beaverhead-Jefferson Rivers, and Big Hole River drainages in Upper Missouri River above Great Falls in Montana. Montana populations were mainly fluvial (stream-dwelling), except for adfluvial populations (reside in lakes and spawn in streams) in Upper Red Rock Lake and Lower Red Rock Lake and possibly Elk Lake.

Arctic grayling in Michigan and Montana were separated from more northern populations during the last glacial period. Although no morphological differences exist among North American populations, extant populations of Arctic grayling in Montana exhibit unique genetics when compared to Alaskan and Canadian populations. Thus, Montana Arctic grayling are both geographically and biochemically identifiable from northern populations. Additional research has shown that the fluvial population in the Big Hole River is genetically different from populations in the Red Rock Lakes and other lakes where they have been introduced.

Context Map

Fluvial Arctic grayling in Montana were irregularly distributed but locally abundant in the upper Missouri River until the end of the 19th Century. By 1950 fluvial grayling had become rare throughout their distribution and today the only viable fluvial population that remains is in the Big Hole River. Overharvest, introductions of non-native fishes, and habitat degradation are common explanations for the decline of fluvial grayling in Montana. In contrast, Arctic grayling have been widely introduced into mountain lakes where they now have viable lacustrine populations. These lake populations sometimes exhibit adfluvial characteristics and grayling can be found sporadically in adjacent streams.

In response to the decline of fluvial grayling, several partners initiated the Arctic Grayling Recovery Program in 1987. The Program goals are to identify and offset threats to grayling and develop a fluvial brood stock for reintroduction efforts. Conservation efforts have improved dramatically, and efforts have been made to reintroduce fluvial grayling back into historical habitats such as the Ruby, Beaverhead, and Sun Rivers. A Candidate Conservation Agreement with Assurances (CCAA) has been developed to improve and protect grayling habitat in the Upper Big Hole River. The CCAA is an agreement with the U.S. Fish and Wildlife Service whereby property owners agree to manage their land to alleviate threats to fluvial arctic grayling. Property owners then receive assurances against additional regulatory requirements should the Arctic grayling be listed under the Endangered Species Act; a recent petition to list fluvial Arctic grayling was denied in 2007 by the U.S. Fish and Wildlife Service because fluvial Arctic grayling do not constitute a species, subspecies, or distinct population segment.

Our CSI analysis incorporated key grayling data from the Montana Department of Fish, Wildlife and Parks, as well as various other sources. A complete list of data sources is provided in the ‘Rule Sets and Data Sources’ document.

Key CSI Findings

• Arctic grayling currently occur in all subbasins within their historic range in Montana
• Although grayling occupied few lakes historically, viable populations have been established in many mountain lakes where they sporadically enter tributary streams
• Introduced lake populations are often abundant whereas grayling are rare in riverine populations
• Arctic grayling have very low susceptibility to disease in the wild, including a low susceptibility to whirling disease
• The Big Hole River contains the last remnant fluvial population of Arctic grayling in Montana
• Most subwatersheds along mainstem rivers have poor watershed conditions
• Over half of all subwatersheds scored 1 for water quality conditions due to agricultural lands, roads along streams, and streams classified as impaired by the State of Montana
• There is wide range of future energy development threats within the historic range of grayling in Montana
• Seventy percent of subwatersheds have a moderately-high to high risk of being impacted by increased temperatures, winter flooding, wildfires, and drought due to climate warming
• Brown trout threaten existing stream populations of grayling as well as reintroduction efforts

Prepared by Dan Dauwalter, September 2009

Table 1. CSI scoring result summary for

Conservation Strategies Map