Thymallus arcticus (Pallus, 1776)
The oldest recorded age of Arctic grayling was 18 years. The heaviest published weight for Arctic grayling was 3.8 kg (8.4 lbs.) Arctic grayling in Montana have been recorded swimming 60 miles in between habitats in Big Hole, Montana.
SIZE: Common length for Arctic grayling is 34.3 cm (13.5 inches) with the longest reported specimen being 76 cm (30 inches) in length.
RANGE: Arctic grayling are native to drainages of the Arctic Ocean, Hudson Bay and Northern Paciﬁc Ocean in North America and in Asia. Two distinct populations historically inhabited waters in Michigan and Montana. The distinct population of Arctic grayling in Michigan is now extinct. Arctic grayling are still present in southwestern Montana. Unfortunately, there has been a signiﬁcant decline in the range and abundance of the distinct population that was widespread in the Missouri River basin above Great Falls Montana. The remaining grayling population in Montana now resides in the Big Hole River, upstream from Divide, Montana.
HABITAT: Arctic grayling inhabit open water in clear, cold, medium to large river and lakes with high concentrations of oxygen. Adult Arctic grayling spawn in mountain streams that have a strong current in shallow water with a rock and gravel bottom.
DIET: Young grayling feed on zooplankton, with a gradual shift to immature insects as the grow older. Adult grayling feed on surface insects but also on ﬁsh, ﬁsh eggs, lemmings, and planktonic crustaceans.
Arctic grayling begin to spawn between the ages of 5 and 7 years. In the spring, adult Arctic grayling move into tributaries and male Arctic grayling begin to establish territories before the females arrive. Adult grayling then begin to school and will eventually begin to reproduce by broadcast spawning.
In early fall, Arctic grayling will begin to slowly migrate back to overwintering areas that are normally downstream of their feeding areas.
As far back as 1991, the U.S. Fish and Wildlife Service (FWS) was requested to consider listing the ﬂuvial grayling population of the Upper Missouri River as a Distinct Population Segment (DPS) under the Endangered Species Act. In 2014, the FWS announced that listing the Upper Missouri River Distinct Population Segment of Arctic grayling under the Endangered Species Act was not warranted.
This ruling is a direct result of Federal, state and private partners working together to address multiple factors that have been negatively impacted the Upper Missouri River distinct population segment since 1991.
The Arctic grayling is a migratory fish. During the winter, these fish are found in the deep pools of river systems where the water never freezes during the winter. In late spring to early summer these fish will migrate upstream to their traditional spawning areas.