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INSTREAM FLOWS TO ASSIST THE RECOVERY OF ENDANGERED FISHES 5 Methods and Approach Review of Information I located and read peer-reviewed publications and unpublished reports pertaining to the ecology of the fishes, along with documents providing ra- tionale and data for flow provisions recommended by the U.S. Fish and Wildlife Service. Also, I dis- cussed data, rationale, and issues related to flow provisions with researchers, management person- nel, and persons with detailed knowledge of issues pertaining to provision of instream flows. Litera- ture cited in this report includes works that I determined to be most pertinent to an informed discussion of instream flow provisions in the con- text of the Upper Colorado River Basin and its rare, endemic fishes. My analysis was limited to review of documents and discussions of data with researchers. There- fore, judgments and conclusions depend on the quality and quantity of data presented in the docu- ments or provided to me in unpublished form. However, I noted from the outset that many of the key observations about these fishes and the rivers in which they live have been published in peer-re- viewed literature. Indeed, the occurrence of peer- reviewed papers is high in relation to the dollars invested in research on these fishes compared with other multimillion dollar programs I have re- viewed (i.e., Glen Canyon EIS; Columbia River Fish and Wildlife Program). Reviewed publication does not guarantee accuracy of data or interpreta- tions, but it is the best standard of credibility we have in science. Peer Review and Schedule During the study period, which began in Octo- ber 1992, I reported monthly to the Instream Flow Subcommittee to facilitate communication and un- derstanding of the objectives of the study, my ap- proach, and understanding of issues. Assembly and review of literature and dialog with persons working on the problem were completed in May 1993. I was assisted in preparing this report by advice and comment from an expert panel consisting of Edmund D. Andrews (U.S. Geological Survey, Boulder, Colorado), William J. Matthews (Univer- sity of Oklahoma Biological Station, Kingston), and James V. Ward (Colorado State University, Fort Collins). I met with the expert panel 18-19 April 1993 in Grand Junction, Colorado. I provided the panel with a preliminary version of this report, and we viewed sites on the Colorado and Gunnison rivers from aircraft, visited sites in the 15-mile reach with Doug Osmundson (U.S. Fish and Wild- life Service, Grand Junction, Colorado), and dis- cussed my review and preliminary conclusions. Written reviews of first and second drafts of this report were provided by the expert panel and mem- bers of the Instream Flow Subcommittee. Many other scientists and experts working in the Upper Colorado River Basin also provided written com- ments on the second draft. All the comments I received were insightful, and I attempted to ad- dress all concerns that I felt would improve the report. I was especially cognizant of comments by the expert panel, and the panel's input is evident throughout the document. However, I take full responsibility for the accuracy and completeness of information and conclusions in the report. Ecological Context for Instream Flow Analysis I approached this analysis from an ecosystem perspective, recognizing that ecological processes or management actions in one subbasin or river reach may influence processes in others (i.e., sys- tem components are ecologically interconnected). For example, migrations by fishes ecologically in- terconnect the entire river system, except as influ- enced by dams, which usually block upstream movements. Dams and reservoirs rarely prevent fishes from moving downstream, although mortal- ity may be high in passage, and conditions down- stream from the dams may or may not favor colo- nization by fishes living upstream from the impoundment. My point is that reaches in the river system where the endangered fishes live (i.e., downstream from the larger dams) are hydrologi- cally and ecologically connected to upstream reaches, where the endangered fishes may have never existed. Interactions between flow dynamics and channel and floodplain features vital to the existence of the endangered fishes also occur from river reach to catchment scales and represent an- other example of ecosystem connectivity. Hence, the ecosystem in this analysis included the entire Upper Colorado River Basin (Fig. 1). Uncertainty exists as to whether ecological and water regulation processes in Lake Powell have significant influences on the ecology of the Upper Colorado River Basin. Regulation of Lake Powell is influenced by delivery of water from the Upper Colorado River Basin, and the reservoir is a source