Hanging by a fin – Westslope Cutthroat Trout in the Porcupine Hills.
There are few places left in southern Alberta away from the mountains where you can find native trout. With declining native trout and char populations across the province, many of the streams in the foothills of Southern Alberta are no longer occupied by Westslope Cutthroat Trout and/or Bull Trout, with both species now listed as Threatened under the federal Species at Risk Act. Westslope Cutthroat Trout are perhaps in greatest danger, found in a mere 29% of the watersheds they originally occupied, with small isolated populations hanging by a fin high up in the watersheds where they remain. The causes for the decline are diverse and range from habitat degradation, fragmentation, and overfishing to invasion of watersheds by non-native salmonids like the Rainbow Trout which hybridize with Westslope Cutthroat Trout, compromising the genetic integrity of the small remaining populations – many pure Cutthroat Trout populations are the result of isolation above hanging culverts or natural barriers such as waterfalls which prevent Rainbow Trout from moving in.
The rarity of Westslope Cutthroat Trout in the region and the pattern of decline across their range underscores the importance of protecting the greatest number and diversity of populations possible across their range. In the Oldman River Watershed, the Willow Creek sub-basin holds some of the last remaining populations of the species in Alberta not found in the mountainous headwaters. These populations exist in a handful of small groundwater-rich streams flowing out of the Porcupine Hills – a striking landform east of the front ranges, elevated high above the prairies to the east and home to a diverse array of plant and animal species. The Porcupine Hills are comparatively warm and dry with montane forests and rough fescue grasslands, lacking completely the alpine and subalpine drainages commonly associated with Westslope Cutthroat Trout. In addition to small populations in Beaver Creek, Sharples Creek, and Playle Creek, the aptly named Trout Creek still holds at least one small population of near-pure Westslope Cutthroat Trout (<5% Rainbow Trout genes). TUC has been following events in the Trout Creek watershed for over 10 years, during which time the creek has undergone dramatic changes, primarily due to the stream channel splitting and scouring out roads and motorized vehicle trails located in the floodplain during floods in 2005, 2008, and 2013. These changes have resulted in Trout Creek shifting across the valley bottom away from the historical channel, rich with groundwater and well shaded from a mature riparian forest, to the scoured out former roadbed which offers little cover for fish and is wide, shallow, and relatively featureless.
In order to rehabilitate habitat for Westslope Cutthroat Trout, TUC began investigating the possibility of realigning the stream to its pre-flood channel to restore the high-quality habitat available prior to flooding. In 2011, Matrix Solutions Inc. conducted a fish habitat assessment in 2011 to determine whether it would be better to improve the new channel or to reconnect the old channel, it was deemed that realigning the stream would be the best option to restore fish habitat. In 2019, Matrix Solutions used updated information to complete a detailed design for the realignment project. With all the pieces needed to proceed to the next phase, TUC launched the multi-year Cutthroat Trout in Porcupine Hills Environmental Rehabilitation (CIPHER) Project with funding through the Environmental Damages Fund (EDF) administered by Environment and Climate Change Canada until March 2022. The CIPHER Project partnership includes Cows and Fish, Oldman Watershed Council, MD of Ranchlands, Alberta Environment and Parks, Alberta Agriculture and Forestry, and the TUC Oldman River Chapter. The CIPHER Project is looking forward to a productive 2020 field season with the major channel realignment works tentatively planned for September 2020, followed by several planting workdays to improve riparian health along several reaches of the pre- and post-flood channels. In addition to the channel realignment, TUC will be conducting additional site assessments throughout the watershed to identify other rehabilitation opportunity areas to tackle in 2021. Helping to guide this work is the Road Erosion and Delivery Index (READI) model, developed by Alberta Agriculture and Forestry and the Foothills Research Institute to help identify areas where erosion and sedimentation could be impacting streams and prioritize where rehabilitation efforts can have the greatest impact. Our hope is that by 2022 we will have made a big enough impact in the watershed to ensure that this unique population can continue to persist, and potentially even expand. Long term efforts in the area will be needed to address the threat posed by Rainbow Trout. Alberta Environment and Parks are working to better understand the genetic makeup of populations in the area and developing strategies to help protect and recover pure or near-pure populations of Westslope Cutthroat Trout.