Aquatic Species at Risk – Dolly Varden (Western Arctic populations)

Description
Habitat
Threats
Further Information
Scientific Information

Description
The Dolly Varden (Salvelinus malma) belongs to the salmon and trout family (Salmonidae), with members that may be anadromous (use both seawater and freshwater during their lifecycle) or non-anadromous (freshwater only). There are two subspecies recognized in Canada - Western Arctic populations, or "northern form" (S. malma malma) and the Pacific populations, or "southern form" (S. malma lordi). The northern form Dolly Varden has the following characteristics:

• Body is laterally-compressed, with large eyes below the top of a round, medium-sized head;
• Caudal peduncle is long and wide; the caudal fin is broad, flat and unusually unforked;
• Juveniles are brown with a whitish belly, with small red spots on the sides and back, and 8 to twelve rectangular parr marks on their sides and back;
• Adults have small, pale-pink or red spots with surrounding halos;
• Spawning sea-run males are brightly coloured and will develop a hook in the lower jaw; females, non-spawners, and non-anadromous males are more muted in colour; and
• Sea-run adults reach over 350 mm in length, while non-anadromous adults are 300 mm or less.

© Joseph R. Tomelleri

Habitat
The Western Arctic populations of Dolly Varden is found in northeastern Eurasia and northwestern North America. In North America, the Western Arctic populations ranges north from Bristol Bay along the north slope of Alaska and the Yukon Territory, and east to the Mackenzie River. In Canada, the Western Arctic populations occurs in drainages that flow into the Beaufort Sea. Approximately five to 10 per cent of the global population exists within Canadian waters. Population sizes are largely unknown, with information limited to selected sites.

Distribution map of Dolly Varden (Western Arctic populations) in northwestern Canada and Alaska.

Several different life history types of Western Arctic populations Dolly Varden exist: i) anadromous (sea-run) types that reside in their natal drainage for about three years, before migrating out to sea to feed for the summer; ii) non-anadromous (freshwater) males that live alongside anadromous fish in the fall and winter and reproduce by "sneaking" into redds to spawn with anadromous females; and iii) other non-anadromous types that are found above falls, a long distance from the sea, or in lakes. Both anadromous and non-anadromous types spend the fall and winter in freshwater environments that are well oxygenated with abundant shoreline cover and vegetation. Spawning occurs in the fall in headwater streams where the females bury their eggs in the gravel. Fry emerge in May or June. The anadromous Dolly Varden remain in their freshwater drainages for about three years, and are known as "parr" before undertaking their first migration out to sea. At this life stage, they evolve into "smolts" and develop the ability to live in sea water. In the fall, they return to freshwater. The non-anadromous types remain in freshwater environments throughout their lives.

Threats
Climate change, particularly the trend towards drier and warmer climates in the Western Arctic, is a key concern. Lower water levels and reduced groundwater flow may have a dramatic impact on Dolly Varden habitat, particularly for spawning and overwintering. Other threats include overfishing, offshore development that impedes the migration and movements of Dolly Varden, and land-based industrial and infrastructure developments that impact freshwater system flows and water quality.

Further Information:
For further information, visit the SARA Registry at www.SARAregsistry.gc.ca or www.COSEWIC.gc.ca.

Scientific Information:

Scientific name: Salvelinus malma
SARA Status: Under consideration
COSEWIC Status: Special Concern (November 2010)