Hydrologic modification for habitat improvement in the Finger Lakes Barko, J. W., R. F. Gaugush, W. F. James, B. J. Johnson, T. J. Naimo, J. T. Rogala, S. J. Rogers, and D. M. Soballe. 1993. Hydrologic modification for habitat improvement in the Finger Lakes: Pre-Project Report Number 2, 1993. U.S. Fish and Wildlife Service, Environmental Management Technical Center, Onalaska, Wisconsin; U.S. Fish and Wildlife Service, National Fisheries Research Center, La Crosse, Wisconsin; and U.S. Army Corps of Engineers, Waterways Experiment Station, Eau Galle Limnological Laboratory, Spring Valley, Wisconsin, April 1993. EMTC 93-T002. 57 pp. (NTIS # PB93-181865) ABSTRACT The Finger Lakes Habitat Rehabilitation and Enhancement Project(HREP) is intended to improve winter habitat conditions for fish in a series of interconnected backwater lakes of the Mississippi River near Alma, Wisconsin. Winter habitat requirements (temperature, flow velocity, and dissolved oxygen) for the target fish population in the Finger Lakes have been defined and limnologcal efforts have been aimed at quantifying the spatial-temporal patterns and interrelationships among water movement, oxygen, and temperature. The progress to date (pre-construction) has included detailed investigations into (1) system hydrology (including dye-tracer studies), (2) oxygen supply and depletion, (3) temperature regime, (4) aquatic vegetation distribution, composition, and abundance, (5) macroinvertebrates, and (6) target fish species movements and food base. It is clear from these studies that the HREP project now under construction will alter conditions substantially in the Finger Lakes. However, the overall biological response of the system to these changes is difficult to predict with precision at this point in the study. KEYWORDS aquatic habitat, rehabilitation, Upper Mississippi River, bluegill, fish, backwater lakes