Effects of Flow Changes on Fish – Comparative Systematic Reviews

The Canadian government has embraced the concept of using scientific evidence in decision making, and has recently made significant investments in its science-based departments to support this priority. It is also recognized that one of the best ways of compiling scientific evidence is to thoroughly examine what is known about critical questions by conducting a literature review, meta-analysis, and gap analysis. To that point, contemporary standards for evidence synthesis as embodied by the Collaboration of Environmental Evidence (CEE) standard systematic literature reviews are being used by the Canadian federal government to support evidence-based decision making and policy development. A systematic review is an enhanced form of literature review that directly addresses a specific policy or management-based question, often incorporating a rigorous statistical meta-analysis of existing research. Systematic reviews can strengthen science-policy interactions by ensuring accessibility of the best available evidence, yielding more-efficient and less-biased information for decision making than by drawing on expert opinions or more traditional literature reviews, and working towards ensuring that management interventions and policy are based on the most comprehensive scientific information. The contractor will conduct 2 systematic literature reviews and meta-analyses that follow the standards established by the CEE on the effects of flow modification on fish production, specifically: 1) What is the impact of changes in flow magnitude due to hydroelectric dams on fish abundance in North America?, and 2) What is the impact of natural changes in flow magnitude on fish abundance in North America? These two systematic reviews could then be compared to assess if the response of fish to changes in flow depends on the cause. Secondary Questions to be addressed qualitatively in narrative review where possible, but quantitatively addressed with meta-analysis if data allows, include: a) What are the key parameters to assess when determining whether proposed flow regime changes will have an impact on productivity? b) How would one assess the impact of flow regime changes on fish productivity? c) What is an appropriate sampling methodology to determine impacts of flow regime changes on fisheries productivity? d) How many years should monitoring occur to properly assess the impact of flow regime changes on productivity? The question “What are the impacts of flow regime changes on fish productivity in temperate regions?” was the topic of a systematic map already completed and has been submitted for primary publication in the journal Environmental Evidence. The systematic map provides an overview of the existing literature base on the impacts of flow regime change on fish productivity in freshwater and estuarine fluvial environments. This systematic mapping exercise described the quantity and key characteristics of the available evidence, identified evidence clusters, and knowledge gaps. The systematic map also identified subtopics that are sufficiently covered by existing studies to allow full systematic reviewing, and has identified that sufficient literature exists to support the completion of the two systematic reviews to be completed herein.