The Bow River is considered a world-class trout fishery and is a unique and valuable feature in Calgary. This recreational fishery is a significant attraction to locals and tourists, worth an estimated $24.5 million each year.
Recent media attention to a research paper has prompted much discussion about the state of the Bow River fishery, particularly the Rainbow Trout population. The paper, published in the Canadian Journal of Fisheries and Aquatic Science, was led by fisheries biologists from the Department of Biological Science at the University of Calgary and provincial government biologists. The study analyzed data collected by provincial Fisheries Management between 2003 and 2013 and the results showed a decline in the adult Rainbow Trout population by as much as 50%.
There could be a variety of reasons for this decline and in fact, it could be multiple stressors acting together. The researchers explored three of the most likely scenarios that may have contributed to the decline: whirling disease, floods, and fishing. Whirling disease was confirmed in the Bow River in 2016 but it is not known when it first arrived in the province. Alberta tested for whirling disease between 1997 and 2001 but it was not detected and no additional sampling for whirling disease took place again until it was observed and confirmed in 2016. Dramatic declines in Rainbow Trout populations have been observed in other regions as a result of whirling disease. The decline in Rainbow Trout observed in the Bow River is similar to the pattern of decline caused by whirling disease in other jurisdictions. However, impacts from whirling disease can be highly variable and there are very few options to treat or manage whirling disease aside from preventing the spread to other waterbodies.
Two major floods also occurred during the study period in 2005 and in 2013, which could have also affected the population. However, the data suggested declines continued in non-flood years and existing science suggests the effects of floods can also be highly variable, sometimes causing declines and sometimes resulting in increases to populations.
It is also probable that high angling effort on the Bow River has contributed to population declines. The Bow River has the highest angling effort of any fishery in Alberta. Although the river is managed as a catch-and-release fishery, there are still impacts associated with catch-and-release. Even when accidental mortality is very low, a cumulative impact to the population can occur when angler effort is high. When an angler carefully releases a fish it may swim away and recover, but what happens the next several times that fish is captured and handled? Angling pressure can also impact how well populations can respond to other stressors like flooding and/or disease outbreak. Locally, the Bow River Chapter ramped up angler education through brochures, presentations, and social media. TUC also recently became an official partner of the KeepEmWet movement, promoting responsible catch-and-release practices. Sometimes responsible catch-and-release fishing means not fishing at all. In recent years, we have seen voluntary angling closures along the Bow River and other systems as a result of low stream flows and/or high temperatures – times that fishing can cause undue stress on fish.
There is no question that Rainbow Trout population declines in the Bow River are real and alarming. Although not native to the Bow River, Rainbow Trout are naturalized following stocking efforts between 1933 and 1947. The Bow River is a valuable fishery economically and provides a unique opportunity for a quality fishing experience near an urban center. The silver lining to this bad news is that the problem has been identified and quantified and this prompted provincial Fisheries Management to collect more data on both the fish population and angler effort along the Bow River in 2018. We hope that this news will also prompt officials to invest in additional and more advanced water quality monitoring of inflows, ‘fish friendly’ shoreline solutions and natural solutions to flood management. In addition, we look forward to the analysis of data from 2013 to 2018.
While there is no reason to expect a rebound or stabilization of Rainbow Trout in the last five years, this information will help in the management of this system. The challenge now is determining how best to act upon this information and decide which management option(s) can be used to stabilize or improve the population. With the results of this study and additional fisheries data collected in 2018, TUC believes that more informed decisions can be made to protect this valuable fishery.
An effective adaptive management cycle requires rigorous data collection and analysis followed by management actions. For adaptive management to work, the cycle must continue and management has to respond to new information in a timely manner.
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