Native Trout - Bull Trout and Westslope Cutthroat Trout

The cold running streams and lakes of western Alberta are home to a number of native fish including bull trout and westslope cutthroat trout. These native species contribute to Alberta’s biodiversity, are sought after by anglers and act as indicators of our headwaters health.

Bull trout are a long slender fish with a large head and jaws – thus the name “bull.”  Westslope cutthroat trout display orange-red streaks beneath the lower jaw – giving the species its name -  and spawning fish often develop a bright red colouration over their entire body.

Bull trout and cutthroat trout were of the first fish to recolonize western Canada after the last glaciation approximately 13,000 years ago and are adapted to cool waters protected by riparian vegetation. Westslope cutthroat trout prefer temperatures ranging from 9-12°C and bull trout require water temperatures below 18°C. Both species were once common in Alberta but have experienced drastic declines. Today most populations are limited to the less accessible upstream reaches of streams and rivers in the eastern slopes of the Rocky Mountains. In the Bow drainage westslope cutthroat trout now occupy less than 5% of their historical native range outside of Banff National Park. 

Bull trout and westslope cutthroat trout are listed as Threatened in Alberta.  The Alberta population of westslope cutthroat trout is also listed federally as Threatened under the Species At Risk Act and bull trout in the North and South Saskatchewan River basins are recommended to be listed as Threatened by COSEWIC.

The threat

Habitat degradation, overharvesting and the introduction of non-native species (through increased competition and hybridization) have all contributed to the decline of bull trout and westslope cutthroat trout.  As these fish species rely on cool, clean waters, the decline of populations in southern Alberta can act as an indicator of the state of our watersheds and quality of water for human use.

Mining, logging, agriculture, road construction, irrigation, dams, grazing and motorized recreation can alter surface and groundwater flows and cause sedimentation to accumulate in waters.  Resource exploration has led to a dramatic increase in road density and access into native trout habitat.  In many areas these roads also lead to increases in OHV traffic, leading to increased stream bank erosion and sedimentation as well as increased angling pressure, as streams become more accessible.  Logging can result in faster runoff events and flooding as well as cause changes in the groundwater recharge and seasonal flows.   These developments also potentially decrease canopy cover and increase the temperature of streams. 

Although protected areas exist on the eastern slopes of Alberta’s Rocky Mountains, they are often small and do not necessarily encompass all the habitats required by the various life history stages of some bull and cutthroat trout populations, particularly migratory forms.

Given the species’ cold water requirements, bull trout and westslope cutthroat trout may be especially vulnerable to climate change. As water temperatures increase, areas may become less suitable for bull trout and cutthroat trout. Increasing water temps may also give nonnative fish a competitive advantage over these native species in marginal habitats. Thus, ensuring intact habitats continue to exist on our eastern slopes is an important adaption method to ensure the recovery of these species.

Whirling Disease

The Canadian Food Inpection Agency (CFIA) found the presence of whirling disease in the fish at Johnson Lake in Banff National Park on August 23, 2016. This is the first time this disease has been confirmed in Canada. Though the disease is not harmful for humans, it is harmful for trout and salmon species in their younger life stages. A parasite infects the fish causing them to swim in a whirling motion and it can cause deformities of the body and head. Overall deaths of infected fry and fingerlings can reach 90 percent. It's important to clean all aquatic equipment, clothing and footwear when leaving a site. For more information or to report a suspected case of Whirling disease contact the CFIA.  


What CPAWS is doing

CPAWS Southern Alberta works with scientists and other conservation organizations to highlight the cumulative impact of resource exploitation and use of the eastern slopes of Alberta and identify solutions.  We are currently working on a vision for ecosystem-based management of Alberta’s southern eastern slopes and will be engaging with the Government of Alberta on the linear density management framework as part of the land-use planning process. CPAWS Southern Alberta is part of the Crown of the Continent Conservation Initiative looking at climate adaption strategies through landscape conservation, including conservation of native trout habitat.

CPAWS Southern Alberta also encourages the government to implement the strategies outlined in the Westslope Cutthroat Trout Recovery Plan and the Bull Trout Conservation Management Plan.

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