SS4.05 Tribute to Thomas Frost
Date: Monday, June 10, 2002
Time: 2:15:00 PM
Location: Sidney
 
GonzalezMJ, Miami University, Orford, USA, gonzalmj@muohio.edu
Paul, D, W, Wright State University, Dayton, USA, 
Pollard, A, I, University of Wisconsin, Madison, USA, 
Vanni, M, J, Miami University, Oxford, USA, vannimj@muohio.edu
 
EFFECTS OF PREDATION BY GIZZARD SHAD (DOROSOMA CEPEDIANUM) ON RESERVOIR ZOOPLANKTON COMMUNITIES
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We compare prey selectivity by larval gizzard shad in a hypereutrophic reservoir (Acton Lake, Ohio) between years with different zooplankton composition. Zooplankton abundance was higher in 1996 than 1997. Rotifers dominated the zooplankton community (48.28% in 1996 and 92.31% in 1997) when larval gizzard shad were present in the lake. The proportion of cladocerans and small copepods was higher in 1996 (31.6%) than 1997 (6.7%). Mean density of larval gizzard shad was lower in 1996 (2.2 ind/m3) than in 1997 (7.4 ind/m3). The maximum larval gizzard shad abundance was 10.4 ind/m3 in 1996 and 35.6 ind/m3 in 1997. We calculated prey selectivity indices (Chessonís Selectivity Index) on three larval fish sizes (< 10.5 mm, 10.6-15.0 mm and >15.1 mm) and estimate gizzard shad consumption rates on zooplankton. All size classes in both years strongly selected for rotifers, particularly Asplanchna sp. Our results suggest that rotifers, which are commonly excluded from studies of feeding preference, may be important food sources for gizzard shad larval stages in reservoirs. Predation by larval fish may represent a significant mortality source for several rotifer species.