Fish Community Response to Stream Flow Alterations in Wadeable Missouri Streams
July 2015 - June 2020
- Missouri Department of Conservation
Ensuring adequate water quantity and quality in stream, riparian, and wetland systems is a pressing issue worldwide and the science related to stream flow management is rapidly evolving (Arthington and Pusey 2003; Poff et al. 2003; Richter 2003; Petts et al. 2006). In the last 10 years the number of research studies evaluating ecological flows has quadrupled. Therefore, researchers, managers, and policy makers need to keep up to date on the latest research to help inform ecological flow decisions. The Missouri Department of Conservation (MDC) has made it a priority to be at the forefront of ecological flow science and to understand how flow alterations affect riverine systems and their biota. The information needed to address the diversity of ecological flow issues that will continue to arise due to climate change, increasing human population, and the associated increased demand for water make stream flow management a complex and long-term issue facing MDC. Recently, ecological flows were identified as one of the top five research needs by MDC’s Fisheries Division and it was listed as one of 20 priority research topics during MDC’s Strategic Research Planning Committee’s efforts to identify long-term research programs. In addition, one of Fisheries Division’s Stretch Goals is establishing adequate ecological flows in Missouri streams in advance of increasing water demands and associated water supply and energy development projects. MDC has broadened its approach to stream flow management by incorporating steps based on an established scientific framework for determining appropriate ecological flows (ELOHA; Poff et al 2010). Over the past two decades, the science of ecological flows has shifted from a narrow focus on minimum flows to a broader view that a complex range of flows is needed to account for seasonal and inter-annual variation in the magnitude, timing, frequency, duration, and rate of change of stream flows (Poff et al. 1997; Richter 2011). This natural flow paradigm recognizes that ecological processes of aquatic and water-dependent ecosystems are driven by naturally variable flows. As a result, flow recommendations now typically use a framework for determining appropriate ecological flows across different seasons and years in an attempt to represent the intra- and inter-annual variability of flow. MDC has been working internally and with partners to develop the information needed for various steps of the established framework. The first step in this effort was the classification of Missouri streams and development of the Missouri Hydrologic Assessment Tool (MOHAT) software to better understand hydrologic alterations (Kennen et al. 2009). Following the development of the classification system and the hydrologic tools their utility were evaluated as part of a cooperative project with the University of Missouri. Recently, MDC funded a literature review to identify fish species responses linked to stream flow alteration metrics, which identified 76 studies that evaluated fish responses to flow with over 400 occurrences for both hydrologic and biologic metrics and over 200 significant biologic responses to varying flow components. Biologic responses are likely species (see Figure 1), system, or region-specific, further emphasizing the complexity of biotic interactions with stream flow and limiting the ability to generate a list of overarching metrics that consistently showed similar responses. The literature review found that information is needed regarding how flow alterations of various types and relative magnitudes affect fish communities in different Missouri streams.