SYMPOSIUM SUMMARY AND CONCLUSIONS James V. Ward and Jack A. Stanford The primary purpose of these proceedings is to document the extent of stream regulation and resulting ecological ramifications on lotic systems, and to provide directions for further research. Although stated in the introductory chapter, it should be emphasized that the intention was to avoid an advocacy stance in this volume. Because this is the first symposium dealing specifically with the ecology of stream reaches below dams, it was deemed appropriate to approach the subject with scientific objectivity insofar as possible, which is not to imply that the editors and authors do not have strong personal feelings regarding stream regulation. The most prevalent riverine environments on earth are indeed regulated lotic systems. That few free-flowing river systems remain was a recurrent message at the symposium. It was in that context which K. W. Cummins stated: "We may never know how large rivers in the temperate zone functioned biologically as the result of hundreds of millions of years of evolution and at least ten to twenty thousand years of acclimatization of resident populations." In this brief summary, focus is directed toward the major con- cepts developed by the authors. Following an examination of abiotic and biotic components of regulated stream systems, geographical vari- ations are analyzed. In the final section, major conclusions are presented. THE NATURAL STREAM ECOSYSTEM The paper by Cummins on unregulated streams provides a scale against which the ecological significance of stream regulation may 377 J. V. Ward et al. (eds.), The Ecology of Regulated Streams © Springer Science+Business Media New York 1979