Grace Marie Wilkinson , Tyler James Butts , Elena Sandry, Martin Simonson, Michael Weber

Bigmouth buffalo (Ictiobus cyprinellus) is a large-bodied planktivore inhabiting shallow waterways in North America and subjected to unregulated harvest throughout much of their native range. Despite high harvest pressure on some populations, we know little about the ecosystem-level effects of lowering bigmouth buffalo densities. To evaluate the effect of bigmouth buffalo density on lower trophic levels we added fish in ambient and harvested densities to a set of ponds and compared plankton dynamics to reference, fishless ponds. Zooplankton biomass declined in ambient density ponds after the fish addition while chlorophyll-a concentrations increased. In the harvested density treatment chlorophyll-a concentrations were similar to the reference ponds despite a decline in zooplankton biomass, likely due to larger zooplankton community size in the harvested ponds exerting greater grazing pressure. This experimental manipulation revealed density-dependent top-down control on lower trophic levels by bigmouth buffalo and the potential for cascading trophic interactions with the harvest of this species. These results point to the need for ecosystem-level studies of the effects of intensive harvest of bigmouth buffalo on water quality.