Changes in the reactive distance of bluegill (Lepomis macrochirus) to various sizes of Daphnia pulex were measured at light intensities ranging from 0.70 to 215.3 lx (0.065–20.0 ft-c) and at turbidities ranging from 1 to 30 Jackson Turbidity Units (JTU). Both reduced illumination and increased turbidity caused substantial reduction in the reactive distance of bluegill for all prey sizes, and particularly for large prey. This result should be considered in efforts to determine fish feeding rates in lakes, and may be particularly relevant to vertically migrating zooplankton, or those inhabiting more turbid waters.