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0'1') , 'J V I V /-. ~t u..:J affected, however. Regulation of the pool at Lake Francis Case is not expected to change substantially to accommodate the diversion. During periods of drought, however, the Fort Randall pool may be drawn down more frequently to elevation 1320 feet m.s.l. as a result of water depletions in the system. The following ecological effects can be expected to result from such drawdowns. Lake drawdown will reduce the volume and quality of aquatic habitat available to biota; pelagic species would become more concen- trated and species interactions would be increased due to a reduction in the carrying capacity. The location and amount of the littoral zone would change. The littoral zone is highly productive in terms of aquatic macrophyte growth and associated epiphytes and invertebrates. Temporary drawdown displaces small prey species from refuge areas afforded in the littoral zone. Because available plant cover is reduced, prey species are more susceptible to predation. Cool-water percids, which include yellow perch, walleye, and sauger, occupy intermediate habitat between the shallow littoral zone and deep profundal zone (Vitchell et al. 1977). Displacement or elimi- nation of this sublittoral area would reduce the population of these species. Entrainment of fish in the diversion intake would also adversely affect fisheries. The adverse effect, however, can be minimized with a proper intake design. The U.S. Fish and Wildlife Service (USFWS) has expressed a concern about the adverse effect and has made recommendations in the Fish and Wildlife Coordination Act (FWCA) Report for this study. ~4