Pegg, M. A., K. S. Irons, T. M. O'Hara, and M. A. McClelland. 2005. Lake Chautauqua habitat rehabilitation and enhancement project fisheries response. Contract report submitted to the U.S. Army Corps of Engineers, Rock Island, Illinois, by the U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, August 2005. 27 pp. Abstract Lake Chautauqua has been an integral component of the Illinois River National Wildlife Refuge System since its purchase by the U.S. Fish and Wildlife Service in 1936. The main goal of this report is to summarize the fish community responses to the Habitat Restoration and Enhancement Program (HREP) construction efforts at Lake Chautauqua aimed at improving habitat for fish and wildlife. Our specific objectives include assessing changes in fish community composition and structure and assessments of length-frequency distributions on the basis of pre- and post-construction collection efforts. Included in this assessment is a summary of the 2002 field collection effort that has not been presented in previous annual reports. Fish community composition showed little variability with 46 species collected in both the pre- and post-sampling periods. Accordingly, Analysis of Similarity tests for differences in species that make up the fish communities between the two periods were not significantly different (R = 0.037; P = 0.60). However, fish community structure appears to be different between the two periods for most gears. Generally, increased abundances of forage species like gizzard shad Dorosoma cepedianum and sport fish like white crappie Pomoxis annularis, black crappie P. nigromaculatus, largemouth bass Micropterus salmoides, and white bass Morone chrysops along with declines of less desirable fish species (e.g., common carp Cyprinus carpio) contributed most significantly to community structure differences. These changes hint at a positive response to the present management practices that have resulted from HREP construction. Keywords fish, Illinois River, Lake Chautauqua, restoration