The Project is primarily comprised of the development of a model to estimate annual fish entrainment losses from the Bow River. The model will be based on fish rescue data collected from 1998-2022, modeled river fish population estimates based on river fish population and abundance data collected from 1999-2021, and a 2003 assessment of fish entrainment losses linking fish rescue information to river fish populations. The model is needed to quantify fish mortality and inform appropriate mitigation measures, fish population management, and ongoing monitoring.
Alberta Environment and Protected Areas, Fish and Wildlife Stewardship Branch (AEPA-FWSB) leads a team of stakeholders conducting a comprehensive evaluation of the status of the Bow River sport fishery and the factors that threaten the sustainability of sport fish populations. Fish entrainment has been identified as a serious threat to the sustainability of the Bow River Rainbow Trout fishery. The cumulative effects model of fish population dynamics will be used to identify and evaluate management actions that can be implemented to meet fisheries management objectives for the Bow River. A comprehensive analysis of population assessment data (1999-2021) was completed in March, 2023 to determine population status and trends in the Bow River between the Bearspaw Dam and the Carseland Weir.
Alberta Agriculture and Irrigation, Water Infrastructure and Operations Branch (AGI-WIOB) is currently renewing its Authorization under the Fisheries Act to operate and maintain water diversion infrastructure in the Bow River. AGI-WIOB has partnered with Trout Unlimited Canada (TUC) to conduct fish rescues at the Carseland Bow River Headworks canal since 1998 and at the Western Headworks canal since 2001, and fish rescue data has been recorded and is included in the provincial Fish and Wildlife Management Information System (FWMIS) database.
The Bow River sport fish population dataset and modelling architecture will be used in combination with the fish rescue dataset as a basis to estimate current and historical fish entrainment losses into the CBRH and WH diversions. A qualified expert is required to develop estimates of annual fish mortality attributable to entrainment at the CBRH and WH diversions. A study completed in 2004 by Dr. Brett van Poorten and Dr. John Post (University of Calgary - under contract to Alberta Environment) provided parameters to estimate fish entrainment losses at the CBRH and to estimate the overall efficacy of fish rescue. These parameters will be combined with modelled river sport fish populations and fish rescue data to provide annual estimates of fish entrainment in the Bow River.
Quantification of fish entrainment losses and the impact of fish entrainment on river fish populations will support applications for renewal of regulatory authorizations. Analysis of fish rescue and fish population data will assist AGI and AEPA to develop appropriate management actions that minimize impacts to the Bow River fishery while providing regulatory certainty for water managers tasked with providing water to irrigators and other water users in the Bow River basin.
While estimation of Bow River fish entrainment is based on extensive river fish population data and fish rescue data, as well as a 2003 study of annual fish entrainment, other southern Alberta water diversion sites have extensive fish rescue data but lack river/reservoir fish population data. The project will therefore include a review of the scientific literature and historical Alberta environmental flow datasets to determine if hydrological variables are correlated with fish entrainment in the Bow River. Preliminary estimates of fish entrainment at other southern Alberta diversions will be developed based on fish rescue data and hydrological data, if possible. If correlation is lacking then recommendations for data collection should be provided so that annual fish entrainment can be estimated at other sites.
Assessment of fish entrainment losses and impacts will be focused on sport fish populations but impacts to non-sport fish species should also be considered where feasible. Assessment of the impacts of entrainment on Species at Risk (SAR) should also be considered at all locations, if possible.
Key outcomes from the project:
• estimate fish losses from the Bow River between Bearspaw Dam and Carseland Weir, in the years 1999-2021, based on the Bow River sport fish population model and fish rescue data, for the Carseland Bow River Headworks diversion and the Western Headworks diversion;
• describe the impact of fish losses to entrainment on Bow River sport fish populations;
• estimate overall effectiveness of annual fish rescue programs (proportion of entrained population successfully relocated back to the Bow River), by fish species;
• assess current scientific literature and historical Alberta environmental flow datasets to determine if hydrological and operational variables (eg: proportion of river flow diverted) affects magnitude of fish entrainment;
• determine if estimates of annual entrainment can be derived from existing fish rescue programs and historical flow information at other headworks locations where fish rescues occur in southern Alberta; if not, make recommendations on data collection requirements that would enable estimates of annual fish entrainment;
• assess magnitude of Species at Risk (SAR) entrainment at all locations if possible;
• provide programming code to repeat analyses in future years, and;
• train regional and provincial fisheries and water management staff to conduct analysis of fish entrainment.
