Roads & Culverts Can Negatively Impact Fish Habitat
A recently published scientific paper titled “Threats to at-risk salmonids of the Canadian Rocky Mountain region” synthesizes the threats facing three native trout species in western Canada: Bull Trout, Westslope Cutthroat Trout, and Athabasca Rainbow Trout. All three species need cold, clean water to survive and access to small headwater streams for spawning.
In August 2019, Bull Trout, Alberta’s provincial fish, was listed under Canada’s Species at Risk Act (SARA) as threatened in southern Alberta, and special concern in northern Alberta and parts of British Columbia and Yukon and Northwest Territories.
In Canada, Westslope Cutthroat Trout can be found in southern Alberta where they are listed as threatened and British Columbia where they are listed under special concern. In Alberta, Westslope Cutthroat Trout were once plentiful in foothills streams but are now constrained to a small and critically disconnected range in the headwaters.
Although introduced Rainbow Trout are found widely throughout the world, the population in the Athabasca watershed in Alberta is the only native population east of the continental divide. This population has shown significant declines from historical abundances and is listed under SARA as endangered.
Protecting Habitat is an Important Line of Defence Against Trout Population Loss
Examining the status of these three species together paints a bleak picture for their future, particularly in Alberta. Future declines are predicted to be 10-70%, 10-100% and 50-100% for Westslope Cutthroat Trout, Bull Trout, and Athabasca Rainbow Trout, respectively within the next three generations (15-30 years) based on their current depleted state and current practices. Declines and range contractions of all three species are linked to four broad categories of threats: non-native species, habitat loss and alteration, angling and climate change. The magnitude of these threats has changed over time. Angling was the largest historical threat, but present-day restrictive regulations have reduced the impact of this threat. The threat posed by climate change is likely to increase for these cold-water fish species as East Slope streams continue to warm. As well, the threat from non-native species, like brook trout, non-native rainbow trout and whirling disease is expected to increase as these species invade into new environments and are helped by warming waters. The threat of habitat alteration and loss has been reduced over time in some ways, with improved industry practices but may also continue to spread with development. The interesting part of considering these three species together is how much their threats vary despite occupying a similar region. There is no one, easy path to recovery for these species.
So what can we do about this?
The choices we make as individuals do matter, whether you work or play on the landscape. For example, following best practices, while angling can reduce impacts from catch-and-release angling. In some cases, this may even mean not angling or not taking photographs of your catch – especially during periods of high water temperature, for example. Helping to reduce the spread of invasive species is another thing everyone can do. Even the basic “clean, drain, dry” is a good rule of thumb to help prevent the spread of invasive species and diseases. Following and continuing to improve upon industry best practices can help to prevent further habitat degradation and fragmentation as development continues in the Rocky Mountain region. For example, road owners (such as municipalities, the provincial government, and industry) have a responsibility to inspect and repair stream crossings that create barriers to fish movement and release sediment and pollutants into water bodies. Protected areas, along with improved recreation and livestock management can also help to prevent habitat damage and/or protect particularly vulnerable populations. It is also important for individuals to engage with their elected officials to ask them what they are doing to support the protection and recovery of these species.
To learn more, we encourage you to read the paper.
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