Westslope Cutthroat Trout (Pacific Populations)

Oncorhynchus clarkii lewisi

SARA Status
No Status
NS
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

SARA Status

  • No Status NS
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX
COSEWIC Status
Not at Risk
NR
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

COSEWIC Status

  • Not at Risk NR
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX

Description

The Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) is one of two Cutthroat Trout sub-species that naturally occur in Canada. The other sub-species is Coastal Cutthroat Trout (O. clarkii clarkii). As one of the first salmonids to recolonize western Canada after the last glaciation, the species is often the only native trout in most of their Canadian range.

The Westslope Cutthoat Trout can be distinguished from the Coastal Cutthroat Trout by the spots below the lateral line on the back half of the body and absent from the front, as well as an orange-red slash below the lower jaw and a longer mouth that extends past the back portion of the eye. These markings help distinguish Westslope Cutthroat Trout from Rainbow Trout (O. mykiss).   

There are three life history forms of Westslope Cutthroat Trout in British Columbia. These are the stream-resident, fluvial and adfluvial forms. Stream residents are relatively small and usually shorter than 200 millimetres in length. They live in small headwater streams above barriers and their movements are limited. Fluvial types migrate between small spawning/rearing tributaries to larger and productive rivers. They are generally over400 millimetres long. Adfluvial types migrate between spawning/rearing tributaries and lakes. If lakes are productive, they can grow to over 500 millimetres long.  

Habitat

The Westslope Cutthroat Trout's current range straddles the Continental Divide. The core range for Pacific populations of this sub-species includes the Kootenay, Flathead, and Pend d'Oreille River systems. These populations live in most tributaries, creeks and lakes. Pacific populations are grouped into seven areas: the Elk Lakes, Flathead River, Upper Kootenay River, West Kootenay Lake, Columbia River, Kettle River, and South Thompson River watersheds. Westslope Cutthroat Trout were also widely introduced inside and outside their natural range for angling.

Westslope Cutthroat Trout live in rivers, lakes, and small streams. The systems they occupy are typically cool, clean, well-oxygenated, and low in productivity. Riparian cover is important for the Westslope Cutthroat Trout – providing stabilized river bank habitat, cool water, protection from predators, and insects for food. The species also seeks cover in undercut banks and pool-riffle habitat.

Spawning Westslope Cutthroat Trout require clean, unsilted gravel and cover. Spawning usually occurs in tributary streams in tailouts of deep pools with large woody debris, boulders or bedrock. Stream resident life history types stay in their natal streams their entire lives. The young-of-the-year quickly migrate to shallow riffle or backwater habitat with protective cover.

Threats

Some major threats to the species' habitat in British Columbia include logging, mining, agriculture, urbanization, and road building. These activities directly modify or destroy the species' habitat. For example, activities that remove riparian habitat reduce a stream's complexity and bank stability. British Columbian populations also face habitat loss and modification from consumptive water use and hydroelectric facilities, fishing, and fish stocking. Fish stocking could threaten the species by competition, displacement, and hybridization.

Further Information

A Management plan for the Pacific populations of Westslope Cutthroat Trout was published in 2017. The plan identified goals and objectives for conservation of the sub-species and its ecosystem. It also summarizes scientific information on Westslope Cutthroat Trout biology and threats to Pacific populations.

The recreational fishery for Westslope Cutthroat Trout has seen stricter regulations since the 1980s. These regulations aimed to restore age structure and reduce harvest. They have been effective in at least the Elk River and St. Mary's River. Larger fish are more common and seasonal catch by anglers has increased by 30 times in these heavily angled areas.

In 2006, the East Kootenay Angling Management Plan was created. The plan summarizes rules for angling on East Kootenay classified waters and their tributaries. The document is under frequent review and had a 10-year review in 2015. Data collection, compliance monitoring and angler education have also occurred though a River Guardian Program as part of the Quality Waters Strategy. The program has contributed to the management of Western Cutthroat Trout.

Stocking of this sub-species is now primarily limited to lakes and occurs only within its native range. The Columbia Basin Fish and Wildlife Compensation Program may be initiating enhancement on some streams in the next five years.

This species is protected under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available on the Species at Risk Public Registry. Additionally, fisheries protection and pollution prevention provisions of the Fisheries Act provide protection to this species.

To find out if this species is protected by provincial or territorial laws, consult the provinces' and territories' website.

Westslope Cutthroat Trout (Pacific Populations)

Photo Credit: J. R. Tomelleri

Photo Credit: J. R. Tomelleri

Scientific Name: Oncorhynchus clarkii lewisi
SARA Status: Special Concern, Schedule 1
COSEWIC Status: Special Concern (November 2016)
Region: British Columbia

Region map

Region map, British Columbia

Did You Know?

Cutthroat Trout can be used an indicator of ecosystem health because of their strict habitat requirements.

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