Studying Sedimentation to Protect Native Trout
By Ann Sullivan
Conservation biologists tend to be a grumpy bunch, according to Dave Mayhood. But with help from stewardship organizations like the Elbow River Watershed Partnership, maybe Mayhood and his colleagues will start feeling positive about changes in Alberta’s water bodies and riparian zones.
Mayhood, an aquatic ecologist and president of FWR Freshwater Research Limited, has been working to bring attention to the state of Alberta’s native Westslope Cutthroat Trout as their population declines and sedimentation of their habitat increases. He is currently researching sediment loading to several streams in the McLean Creek Public Land Use Zone (PLUZ), one of the few remaining areas with genetically pure stocks of Westslope Cutthroat Trout.
One hundred years ago, Westslope Cutthroat Trout were an abundant species in the Upper Bow and Oldman River systems and mostly likely the Milk River too. These days there’s almost nothing left of those pure stocks. It’s a classical conservation issue, says Mayhood: a very small population in a fragmented and highly unproductive habitat. Some of the creeks in which cutthroat are still found are tiny—just several kilometres long and narrow enough to easily jump across. Others, like Silvester Creek in the Elbow River watershed, are loaded with sediment from off-highway vehicle (OHV) traffic, pipeline rights of way and trail and road surface erosion.
Native cutthroat stocks started declining decades ago, through a combination of overfishing and hybridization with introduced trout species. About five year ago, the federal government listed the Westslope Cutthroat Trout as “threatened” under the Species at Risk Act (SARA). Mayhood would argue that the species is endangered, not just threatened, and notes that the government has created a recovery strategy for the species but still needs an action plan to save it.
So, what’s the big deal if we lose a few genetically pure fish stocks in Alberta? Mayhood says that we need every single one of these genetically unique and locally adapted stocks. “When we’re knocking off species at the rate we’re knocking them off now,” he says, “we’re limiting the possibility of future life on the planet.” All life comes from existing life, he adds. “It’s not just a question of ‘it would be nice.’ We need them.”
Silvester Creek, which lies within the Elbow River watershed, provides critical cutthroat habitat. Part of the creek is protected under SARA, but the area is popular with OHV riders, who use a network of official and unofficial trails for recreation. Silvester Creek runs through the McLean Creek PLUZ, designated as an off-highway use area in the 1970s. The trail network that crisscrosses the area adds to sedimentation in local creeks and ultimately in the Elbow River.
Roads and trails are by far the biggest contributors of total suspended solids in streams, Mayhood says. For struggling native trout, it takes very little road development to reduce populations. Cutthroat require pools for spawning, but those pools are often marred by sediment, especially during times of increased runoff from snowmelt and rainfall. Illegal stream crossings by OHVs at any time of year lead to perpetually disturbed trails and increased sedimentation.
Mayhood’s current research project was to look at sediment loading to streams in the McLean Creek area, but because 2017 was such a dry year, the team focused its efforts on identifying sediment sources. They found that McLean Creek, which represents less than four percent of the Elbow River basin, supplied a disproportionate amount of sediment being carried in the river. This year’s very dry conditions will mean study results won’t necessarily represent what’s really going on in the area. “In other years that creek has run like chocolate milk,” he said.
McLean Creek area may require major changes to safeguard fish stocks and habitat, but Mayhood says that restoration work by volunteer stewardship groups, including the ERWP, is a step in the right direction. “I do expect some improvements,” he said, adding, “I have high hopes for the October  work in particular.”
In October of this year, volunteers with the ERWP decommissioned an illegal trail near a bridge at the lower end of Silvester Creek. The group closed access to the trail on both sides of the bridge by digging it up and replacing it with “rough and loose” technique. Volunteers also planted willow stakes to help restore the area and deter OHV traffic.
Along with restoration work, Mayhood would like to see more trail signage in the area to discourage illegal trail use by OHVs. Logging companies now close roads after they finish work in the area, he said, which is also helpful.
Mayhood says fish stocks can recover with a strategy that includes retaining existing stocks, removing non-native fish and protecting watersheds.
Fortunately, the ERWP does just that, working to protect watersheds and enhance fish habitat via riparian restoration and other projects. The Southern Alberta Fish Habitat Enhancement and Sustainability Program and the Westslope Cutthroat Trout Recovery Team are currently working on restoring sites in the Elbow Watershed, including Silvester Creek. For more information, visit the government website here.
“We’ve had this problem for a long time and it’s going to take us a long time to get out,” Mayhood said. “The thing is to get started.” That’s just what stewardship groups like the ERWP have done.
The report on sediment loading to streams in the McLean Creek Area by Dave Mayhood and his team will be available in the new year.
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A heavily-used but undesignated (illegal) trail drains silt steeply downhill to a known cutthroat trout spawning site, Silvester Creek. In partnership with the Westslope Cutthroat Trout Recovery Team, this trail was decommissioned by the ERWP in October 2017. Dave Mayhood photo
In partnership with the Westslope Cutthroat Trout Recovery Team, this trail was decommissioned by the ERWP in October 2017. The site was restored using a variety of techniques including “rough and loose,” spreading woody debris, scarifying and willow planting. The project was partially funded by a Watershed Resiliency and Restoration Program grant. Kelly Dick photo
In 2018, the ERWP plans to work collaboratively with Shell Canada and the Alberta Westslope Cutthroat Trout Recovery Team to restore this site near Silvester Creek. Dave Mayhood photo
Mayhood’s team measures gully erosion more than 1 metre deep on a closed but still heavily-used OHV trail. The fine sediments from this site have been washed downhill into Silvester Creek, critical habitat for threatened native cutthroat trout. Dave Mayhood photo
Once a road surface becomes saturated, even very light rainfall generates muddy runoff to streams. Here several days of intermittent light rain allowed a very light shower to deliver silt-laden runoff to a major tributary of Silvester Creek. Dave Mayhood photo
Filters from water samples show the results of road runoff to Silvester Creek. The upper four rows are from triplicate water samples filtered from four locations along the creek. The bottom row shows filters from triplicate water samples taken from a control site unaffected by road runoff. Dave Mayhood photo