The State of the Bow River Fishery – Trout Population Decline Update

August 31, 2018:

An Update of the original article published earlier this year

The previously reported Bow River Fish Populations Report documented the historical fish population surveys from 1980 to 2007 which at that time supported a sustainable fishery.  The recent retrospective analysis of Bow River Trout Population Surveys by University of Calgary researcher Chris Cahill, entitled, Multiple Challenges Confront a High-Effort Inland Recreational Fishery in Decline  has indicated that rainbow trout populations are in trouble. Data analysis showed that the Rainbow Trout populations may have declined by as much as 50% over a ten-year period from 2003 to 2013. The research indicated that:

“Despite uncertainty in both abundance and trend estimates, these results indicate that Rainbow Trout in the LBR (Lower Bow River) likely declined during both assessment periods. The median posterior estimates for a 10-year standardized population trend were -43.0% using Trendestimated from the 2003-2008 data, and -50.0% using Trend estimated from the 2003-2013 data. Since the size criteria for tagged fish (≥ 250 mm FL) corresponds approximately to the sizes of mature Rainbow Trout (Rhodes 2005), the estimated decline likely represents a large reduction in the number of mature individuals in this population. For example, The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) guidelines state that “in cases where the declines or its causes are unknown” a decline in the number of mature individuals ≥ 30% or ≥ 50% over a period of ten years would qualify a population as “threatened” or  “endangered,” respectively (COSEWIC 2018). Rainbow Trout in the LBR are naturalized (Gilmour 1950), and hence do not qualify for listing as per COSEWIC guidelines; nonetheless,  these criteria demonstrate the magnitude of the decline documented here”. 

Recent stakeholder engagement with  Alberta Environment & Parks has addressed an initiative to stop the decline in Bow River trout populations and hopefully  see improvements in the future.


The first step to a recovery program  is to establish a baseline fish population index that will guide fishery management policy change.

During the weeks of September 10 and 17 AEP will conduct fish populations surveys on the Bow River using the electro-shocking technique.

Bow River Trout Foundation is committed to this process and believes that the first step should be to conduct Bow River fish population monitoring on a regular basis that will give an index for the “The State of the Bow River Fishery”

The State of the Bow River Fishery

The Blue Ribbon Bow River needs your help. Your donation will assist BRT initiatives to monitor fish population dynamics and advocate for fishery management change.


4 thoughts on “The State of the Bow River Fishery – Trout Population Decline Update

  1. This is disturbing to see that there is a decline in the mature rainbow trout population in the Lower Bow. This year has been a difficult year and I have observed way less fish caught per trip on the Lower Bow. I am hopeful we can all work together and keep this amazing fishery healthy for many generations to come.


    1. Mike: I was out with AEP Biologists this week. It was disturbing to see the electroshocking numbers low in many classes of fish. Next week’s trips within the City of Calgary will see just how many large brown trout are around. But not too many on the days I was out this week.
      Bow River Trout Foundation


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