THE IMPORTANCE OF BIOTIC INTERACTIONS IN SHAPING LARGE RIVER ASSEMBLAGES: ZOOPLANKTON RESPONSES TO THE ARRIVAL AND SUBSEQUENT CONTROL AND REDUCTION OF ASIAN CARP

Zooplankton are a critical structural and functional component of riverine communities and food webs. While obligate and facultative planktivores are common components of riverine assemblages, the arrival and rapid expansion of invasive and planktivorous Asian carps has resulted in an extremely large shift in both the species, size, and amount of plankton in the Illinois River and other tributaries of the Mississippi basin. The potential negative ramifications of further spread to other basins like those of the Great Lakes is so great that a wide variety of intensive control efforts, including removal via commercial fishing, have been instituted. In addition to reducing the potential for further spread, there is a hope that the impacts on the river ecosystem can also be reversed. We will present results of the first 5 years of Asian carp removals on native plankton and planktivorous fish: rotifers respond positively and more quickly the macro-zooplankton and while in general planktivore condition (Bigmouth Buffalo and Gizzard shad) is still lower than pre-Asian carp, there is evidence that accelerating removal efforts can have a positive effect.