The Peace/Williston Fish and Wildlife Compensation Program (PWFWCP)

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Arctic Grayling
Thymallus arcticus

What do they look like?

The grayling are troutlike fishes with rather small but toothed jaws, large scales, and a large and often colourful flaglike dorsal fin. The spectacular dorsal fin on mature males is unique, and even females and juveniles have exceptionally long dorsal fin bases - its base is longer than the head. In mature males, the posterior rays of the dorsal fin extend back almost to the adipose fin, and the pelvic fins are strikingly marked with vivid orange stripes. The dorsal fin has an orange border and is almost blue with numerous spots highlighted with pale haloes. In mature females the dorsal fin is slightly smaller and not as vivid.

Where do they live?

Arctic grayling occur in lakes, large rivers and small streams but, in B.C., they are primarily a riverine species. They often display complex migrations between spawning sites, feeding sites, and over-wintering areas. An annual movement between over-wintering sites and summer feeding sites is a characteristic part of grayling life history. In the upper Peace system, adults over-winter in the lower reaches of large rivers and in embayments where rivers enter Williston Reservoir. Upstream migration occurs in the early spring (at or shortly after ice-out). As adults, the areas used as summer feeding sites shift from smaller streams to mainstem pools, riffles, and runs.

Habitat use by 1+ fish is a bit of a mystery. In the upper Peace system, juveniles appear to use large, valley-floor rivers (e.g., the Parsnip River) as rearing areas. Since spawning typically occurs in smaller tributary streams, and larger grayling usually occur farther upstream than juveniles, the size-based distribution pattern in the upper Peace implies substantial migrations of all size classes.

Typically, young-of-the-year are found along the quiet margins of tributary streams or in slow (<0.5 m / s) side-channels associated with larger rivers. In B.C., young-of-the-year move out of tributary streams and into larger rivers sometime during their first summer. As winter approaches they move into deep side-channels and areas associated with ground water. They over-winter in these areas and, in the spring, shift back into tributary streams.

What is their life like?

Arctic grayling display three life-history patterns: the commonest life history is riverine; however, both adfluvial (migrations between lakes and streams) and lacustrine populations occur throughout most of the species' geographic range.

Arctic grayling spawn in the spring, usually shortly after ice-out when the water temperature rises to about 4 °C. In Northern B.C., spawning occurs from early to late May. Grayling usually spawn in flowing water over coarse (2-4 cm) gravel and cobble substrates. Typically, there is a modest current (0.5-1.0 m/s) and the spawning site is a shallow (10-40 cm) glide or run. Unlike other salmonids, the male chooses the spawning territory. There is no site preparation but the male's activity often sweeps the area clean of silt. Females remain in deeper areas near cover until ready to spawn.

Little is known about the fecundity of B.C. populations, but in other areas egg number ranges from about 1,000-17,000. The eggs are slightly adhesive and denser than water. They are released, fertilized, and then drift to the bottom and become lodged in cracks and crannies in the substrate. The incubation period depends on temperature. Yolk-sac fry are about 11 mm in length and emerge and begin feeding at 14-15 mm.

Depending on stream productivity, young-of-the-year grayling can grow rapidly and occasionally reach about 120 mm in their first year; however, in B.C. most populations reach 60-70 mm by the end of their first summer. Growth gradually slows over the next five years and by their fifth summer they are usually over 250 mm in length and reach about 300 mm in their sixth summer. Most individuals reach sexual maturity after their fifth summer. In B.C., the maximum life span for most grayling is around eight or nine years and very few individuals exceed 400 mm in length.

What do they eat?

Adult grayling forage primarily on aquatic insects and, not surprisingly, their winter diet contains more bottom-oriented insects and fewer surface insects than their summer diet. Adults and juveniles consume a similar range of prey but adults often add small fish to their diet. Lake-dwelling populations often forage on plankton. The young-of-the-year feed primarily on the smaller stages of aquatic insects, especially midge larvae, but as they grow they add drifting nymphs and terrestrial insects to their diet.

What is their distribution? Arctic grayling occur in both North America and Siberia. As the name implies, in North America they are a northern species that extends in a broad band from the west coast of Hudson Bay to Alaska. Historically, isolated populations occurred in upper Michigan and one isolated population still exists in an upper Missouri tributary (Big Hole River) in Montana. In B.C., Arctic grayling are found throughout the Peace and Liard rivers (Mackenzie system), the Yukon system, and in the upper Stikine, Taku, and Alsek rivers (Pacific drainages).

View Peace Williston distribution map.