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Bull Trout have a long and slender body with a relatively large large head and jaws. Their back is olive-green to blue-grey in colour, and their sides are greenish to silvery with small pink, yellow-orange or red pale round spots. Their belly is pale-coloured and may become yellow, orange or red in males during spawning season. Traits that help distinguish Bull Trout from other fish species include pale round spots on their sides and back and the absence of black markings on their dorsal fin. Instead, Bull Trout have a white line on the leading edges of the pelvic and anal fins.

Length varies based upon its life history (see habitat and biology): Resident, 250 to 410 mm.   Fluvial, 400 to 730 mm.   Adfluvial, 400 to 900 mm.

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In Canada, Bull Trout is found in British Columbia, Alberta, Yukon and the Northwest Territories. It  is a coldwater species found in lakes, streams and rivers from sea level to mountainous areas. Its habitat is described best as cold, clean, complex and connected.

In the NWT, Bull Trout are widely distributed, but in low abundance, throughout much of southern (Dehcho) and central (Sahtú) drainages west of the Mackenzie River. The northernmost known location is the Gayna River.


Range map information


Bull Trout, contrary to their name, are not actually trout but are a species of char.  For over a century Bull Trout were thought to be an inland form of Dolly Varden, but in 1980 research proved these two species are distinct.

There are four types of life history strategies used by Bull Trout. The resident form is isolated and spends its life in small rivers or streams. The fluvial form lives in small rivers and streams, migrating between spawning streams and larger streams. The adfluvial form is similar, but matures in lakes rather than streams and rivers. The anadromous form is found only in southwestern British Columbia and Washington, and migrates from spawning freshwater streams to the sea.

Presence of Bull Trout is a good indicator of ecosystem health. It requires cold, clean, and well oxygenated water as well as connected watersheds, making it highly sensitive to habitat changes. 

Spawning occurs in the fall in water temperatures below 10°C in clean flowing streams over cobble or loose gravel. These areas are typically associated with groundwater sources. The female digs her nest (redd) accompanied by a dominant male who defends her eggs from other males. Some males nicknamed “sneakers” are able to mimic females, allowing them to approach close enough to fertilize some of the eggs.

Bull Trout feed on a wide variety of items including other fish. The typical maximum age of Bull Trout is unknown, but specimens have been recorded up to 24 years old. 

The Bull Trout (Western Arctic population) is broadly distributed but populations are never abundant. Little is known about population size and trend in the Northwest Territories. There is some evidence of decline in Alberta.

Bull Trout grow slowly, do not reproduce until they are between five to seven years old, and may not spawn every year. Because of this, they do not recover easier from population declines. 

Industrial activities and infrastructure can degrade or fragment Bull Trout habitat; for example by adding sediment or nutrients, blocking movement of fish, or changing water flow. Bull Trout are difficult to distinguish from other char and trout that are commercially fished, however there is minimal overlap in distribution with these species in the NWT. Other threats include diseases and pathogens, introduced and invasive species, climate change and cumulative effects. 

COSEWIC assessed Bull Trout (Western Arctic population) as a species of Special Concern in 2012 because of small population size, evidence of decline in parts of the range, and biological factors that make it particularly vulnerable to threats. Bull Trout (Western Arctic population) was listed as Special Concern under the federal Species at Risk Act in 2019.

Dehcho Sahtú South Slave