M.J. Cyterski and J.J. Ney, Department of Fisheries and
Wildlife, Virginia Polytechnic Institute and State University, 100 Cheatham Hall,
Blacksburg, Virginia 24060-0321; Voice 540-231-7292;
FAX 540-231-7580; E-Mail mikecy@vt.edu
Keywords: predator-prey interactions, reservoir, bioenergetics,
hydroacoustics
The fishery of Smith Mountain Lake, Virginia, is dominated by native
largemouth bass and stocked striped bass; both feed primarily on alewife and gizzard shad.
Angler pressure to increase striped bass stockings motivated this quantitative assessment
of the adequacy of the prey resource to meet increased predator consumption. Predator
consumption (current demand) was determined using bioenergetic modeling, while prey
production was investigated using hydroacoustic biomass assessment and population
simulations; field data on diets and population dynamics were essential inputs. Presently,
largemouth bass consume 5 kg/ha of alewife and 9 kg/ha of shad annually, while striped
bass utilize 55 and 32 kg/ha of these species, respectively. Hydroacoustic assessment
determined average annual August biomass of alewife and shad to be 36 and 67 kg/ha,
respectively. Population simulations estimated annual alewife production as 73 kg/ha,
while shad production equaled 64 kg/ha. Of this clupeid production, about 90% is currently
being utilized by predators, or is morphologically unavailable. Our findings lead us to
conclude that increases in striper stockings of 50% will be accompanied by any or all of
the following: declines in growth and/or survival of predators, increases in diet breadth
of piscivores, decreasing survival with possible increased growth of clupeids.