Zooplankton and Juvenile Largemouth Bass in Two Ohio Reservoirs

Zooplankton serve as an essential prey item for larval and small juvenile largemouth bass. Differences in zooplankton communities among lakes and across years may help explain temporal and spatial variation in growth rates of age-0 largemouth bass. To better understand how zooplankton could influence early growth in young largemouth bass, we estimated zooplankton abundance and diversity in two Ohio Reservoirs. In 2012 and 2014, we surveyed two very different reservoirs in Ohio: Burr Oak Lake, located in a highly forested watershed, and Deer Creek Reservoir, located in an agricultural watershed. Zooplankton collections occurred weekly May –August at the outflow of each reservoir and were counted and identified in the lab. In Burr Oak, zooplankton densities were consistently greater than in Deer Creek when largemouth bass were dependent on zooplankton as prey. Reservoirs also differed in their seasonal trends of zooplankton abundance. Through the sampling season a decreasing trend in zooplankton abundance was observed in Burr Oak while an increasing trend in zooplankton abundance was observed in Deer Creek. These zooplankton trends offer insight and help explain growth rate differences within and between these two Ohio reservoirs.