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Writer's pictureFreshwater Conservation Canada

Taking a Deep Dive into Quirk Creek Data

By Lesley Peterson Provincial Biologist

TUC volunteers in the Calgary area in years past may recall the Quirk Creek Brook Trout Suppression project with some fondness. This was one of TUC’s longest-running projects, launched in 1998 and continuing until 2015. Dozens, if not hundreds of volunteers participated, and one can see why…volunteering involved fishing a beautiful mountain stream with the opportunity to harvest unlimited Brook Trout. Throughout the project, thousands of non-native Brook Trout ended up on BBQs and frying pans. An added benefit was that volunteers understood they were contributing to science and potentially helping to recover native Westslope Cutthroat Trout and Bull Trout. Sounds perfect, doesn’t it? Many were disappointed when the program was discontinued in 2015 after data analysis suggested not only that the project was likely not meeting the goal of native trout recovery but it may also have been hindering it. Recently, researchers at the University of Calgary completed a detailed analysis of the data collected during the project and wrote a report summarizing their findings. This article provides a very brief summary – the full report was published by Alberta Environment and Parks and is available to download.

Taking a Deep Dive into Quirk Creek Data

Although TUC has been working hard to protect and recover Brook Trout in their native range in central and eastern Canada, it’s a different story out west where Brook Trout pose a threat to native species. Brook Trout stocking programs began in the west in the late 19th century, to create new and varied angling opportunities, likely without much thought to the long-term implications to native species. Brook Trout compete with native trout for space and resources and are aided by their ability to grow quickly and reproduce at a young age.


Quirk Creek is a tributary of the upper Elbow River approximately 50 km southwest of Calgary, within the McLean Creek Off-Highway Vehicle Public Land Use Zone. The creek was historically home to Bull Trout and Westslope Cutthroat Trout. In 1949 the creek was described as “overrun” with Dolly Varden (what we now know are Bull Trout). Brook Trout were first documented in the creek in 1978 and by 1996 they were the dominant species. Concern over the fate of Bull Trout and Westslope Cutthroat Trout led TUC to partner with the Fish and Wildlife Division of the Alberta Government (now called Fish and Wildlife Stewardship Division) to initiate the Brook Trout Suppression Project.


The project was based on the hypothesis that Brook Trout were limiting recovery of native trout and that angling could be a cost-effective method to suppress non-native Brook Trout. To participate in the project, anglers had to pass a fish identification test. Initially, anglers participated in organized outings coordinated and led by TUC and/or Fish and Wildlife. All captured Brook Trout were harvested and then measured and weighed by the volunteer coordinator. If anglers captured Bull Trout and Westslope Cutthroat Trout, they recorded their length and released them. Starting in 2000, experienced anglers could harvest Brook Trout on unsupervised outings and report their catch to TUC. Later, electrofishing was added as a Brook Trout removal method to go along with angling.

Throughout this period, several methods were employed to assess fish populations in Quirk Creek. The Quirk Creek Fisheries Data Series examines these data as well as other factors at play during the project including growth and maturity, stock recruitment, angling catchability and release mortality, and environmental conditions.


So what did we learn? During the project, which involved targeted removal of Brook Trout both by angling and electrofishing, Brook Trout abundance declined from a peak in the late 1990s and early 2000s but increases in Bull Trout and Westslope Cutthroat Trout were not observed as expected. In fact, there has been a continued decline in the density and biomass of large Bull Trout and Westslope Cutthroat Trout since the 1970s. The data also suggests the carrying capacity of Quirk Creek has not been met which means competition for habitat and food is likely not an issue.

Taking a Deep Dive into Quirk Creek Data

The authors suggest a few hypotheses to explain why native trout recovery has not occurred. One is that environmental factors (for example increased temperature, increased flow) have influenced their recovery. It may also be possible that simply not enough Brook Trout were removed. Other studies suggest that in Brook Trout suppression projects where less than 60% of each size class is removed, Cutthroat Trout will continue to decline. And these intensive removal efforts need to be repeated year after year. Finally, the lack of recovery may also be related to incidental “hooking” mortality of native trout captured and released during the project. One reason to suspect this is that it appeared that Westslope Cutthroat Trout recruitment was persistent throughout the study (they kept having babies) but this was not reflected in densities of large fish – which means there may have been some effect resulting in the mortality of large fish specifically, which is consistent with the handling mortality hypothesis. This is perhaps not surprising, given that angling primarily focuses effort on larger catchable-sized fish as opposed to smaller life stages.

TUC is grateful to the many anglers and volunteers that participated in this project. The data collected by anglers has been important and has helped to improve our understanding of Quirk Creek and contribute to advancing the science and understanding of Brook Trout suppression to facilitate the recovery of native trout. The science continues to evolve, and TUC looks forward to working with partners to continue efforts to protect and recover native trout in their native range using a variety of tools available.

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