As icy water rushes past the gravel beds of the Elbow River, a team of volunteers moved slowly downstream Friday morning— their eyes trained on the riverbed, searching for small mounds and dips in the gravel that signal something vital to Calgary’s ecosystem. They’re counting trout nests — known as redds — as part of an annual survey organized by Calgary River Valleys, a volunteer non-profit group and partner of the City of Calgary that’s been tracking brown trout spawning sites for decades. The nests are easy to miss unless you know what to look for. Chris Bjornson, a retired fisheries biologist with Calgary River Valleys says brown trout dig their nests into the riverbed, leaving bright, clean patches of gravel with distinct dips and mounds. “This leaves evidence in the river,” he said. “We can see where exactly where these redds spawn, and we can actually count them, so we can count the number of spawning sites in the river.” Brown trout are one of the principal sport fish in the Bow River, and a portion of the fish come up the Elbow River from the confluence at the Glenmore Dam. The group counts the nests from the dam onwards which prevents the trout from travelling further upstream like they would have before the dam’s construction. The Bow and Elbow rivers support more than aquatic life: the recreational trout fishery on the Bow generates an estimated $39 million annually, part of a larger $115 million river recreation economy in the region. For Bjornson, tracking redds is a crucial part of protecting that value, but also providing a rare look at the health of both the fish population and the surrounding habitat. “The number of redds is sort of an index of the adult population,” Bjornsaid said. “If we have a lot of redds, we know we have good quality habitat — fast-flowing water over clean gravel substrate.” Calgary River Valleys has taken over organizing the effort since 2009, ensuring the count happens every year. “We’ve done it the last 23 of 26 years,” Bjornson said. Calgary River Valley volunteers counted a total of 422 redds Friday. Last year was tied for the highest ever with 427. Recovering after disaster Decades of surveys have revealed major shifts in the trout population including the impact of the 2013 flood. “Through the 1990s and early 2000s, we saw quite a large increase — about a threefold increase,” Bjornson said. “We peaked around 2000, and then it just remained kind of steady, but in 2013 with the flood, we had a very low year — about a 75 per cent decrease.” The low point didn’t last long. “We started to see recovery in 2015,” he said. “Within about seven years after that, we were back up to the peak number of redds we’d ever recorded.” Bjornson added that stable winter flows from the Glenmore Dam help protect eggs buried in gravel until spring. “That steady flow over the winter is actually quite beneficial,” Bjornson said. “The eggs will remain in the gravels in the riverbed until next March.” What the redds signal about water quality Researchers say trout nests double as environmental indicators. “Trout and other salmonids tend to be species that are really sensitive to water quality,” said Kelsey Lucas, an assistant professor of biological sciences at the University of Calgary. “Young fish tend to be even more sensitive to water quality than adult fishes.” Lucas said long stretches of redds — or sudden gaps in where they appear — can offer clues about changes in the river. “If we see nests along the river and then suddenly they cut off, that suggests there may be a shift in water quality,” she said. “It can tell you about areas of the river that are healthier for fish versus less healthy.” Temperature remains the single biggest factor influencing spawning success. “The number one thing we tend to think about for fish is temperature,” she said. “You might get patches of warmer or colder water depending on weather, natural inflows, or effluent releases.” Lucas added that citizen science programs like this one help bridge research and community. “This is not just a one-time event — it happens every year,” she said. “Students I’ve had participate say it’s been a wonderful opportunity to connect with what’s happening in the rivers.” A hands-on river lesson Dozens of Calgarians join the survey each year, motivated by curiosity, stewardship — and sometimes just a love of the cold-weather challenge. “This is an opportunity we get to do once a year when the brown trout are spawning,” said Andi Antal, an environmental educator with the Elbow River Watershed Partnership. “Counting the redds allows us to know how their population is doing.” Trout, she noted, are highly sensitive to climate and habitat change. “Our trout are species that require especially cold and clear water,” Antal said. “There are lots of human impacts that can increase water temperature and that’s what we’re concerned about.” The hands-on work gives volunteers a rare chance to connect with the ecosystem they’re helping protect. “It’s a chance for us to get out on the ground in the watershed to interact with the system itself,” she said. Why volunteers brave the cold Some volunteers have been coming for years, but others are newcomers who feel drawn to the work. “I just love doing this,” said Glenda Misurelli, a repeat volunteer. “Our river is known for its wonderful fish life. It’s an honour and a privilege.” For Joe Fowler, who works with a watershed advisory council, the appeal is both personal and professional. “I love hanging out in the river, especially the Bow and the Elbow,” Fowler said. “Any opportunity to get to know it a little better or look at it in a different way, I love taking those opportunities.” The data, he said, is invaluable. “People really connect to trout,” he added. “Having that information is always really valuable.” Miliana Giesbrecht, a first-time participant who previously worked at the Bow Habitat Station, said the count also offers a chance to reconnect with species she once cared for. “The more time I get to spend with fish, the better,” she said. “Even if I don’t see them today, it’s interesting to go and see where they’re spawning and what they’re doing.”
