Lower Elbow River Brown Trout Redd Survey (2009-present)
As Calgary grows, the Lower Elbow River is coming under increasing pressure from multiple sources. This project involves a visual survey of Brown Trout spawning sites (“redds”) along a 12km reach of the Elbow River, from the base of the Glenmore Dam to its confluence with the Bow River at Fort Calgary.
The 2017 Redd Survey date was on Friday November 10th, 2017. Calgary River Valleys has coordinated this important scientific project since 2009, with the able assistance of a fisheries biologist, Chris Bjornson, from Golder & Associates, and river rafts provided and guided by Rocky Mountain Paddling.
This project generally involves between 10 and 20 individuals going for a “walk in the river” in the shallow sections, and riding in the rafts in the deeper sections. Female trout like to spawn in shallow gravel bed areas, and they use their tail to swish away the loose gravel, silt, and algae on the river rocks, in order to deposit their eggs in the now clean depression in the river bed. These eggs are then fertilized by the male trout and covered back over by loose gravel again. As a result, the areas of “clean gravel” in shallow waters, which are the trout nests or “redds”, can be easily seen by a trained observer walking in the river.
There was some concern after the 2013 flood, which resulted in a much lower number of redds in 2013 and 2014, as to whether the Brown Trout would make a resurgence in spawning or not. Since then, the data shows an increase in the number of redds since the lower numbers after the flood in 2013. This is one indicator of an improvement of the health of the river overall.
Download a report made to the Bow River Basin Council’s Quarterly Forum in September 2017 that explains more details about this annual Redd Survey, why we do it, and some of the changes we’ve seen over time: Redd Count Presentation 2017 (1318 KB PDF).