Effect of Spatial Variation on Zooplankton Community Assessment in Fishery Studies

Abstract

Many fishery researchers studying zooplankton abundance and size structure fail to implement a sampling protocol that addresses the horizontal distribution of zooplankton. Therefore, we assessed the horizontal and seasonal differences in the abundance and size structure of zooplankton in a small (43 ha) South Dakota impoundment. We collected zooplankton samples from vegetated, edge, and non-vegetated areas using a 1.5-m integrated tube sampler in May, June, and July 2001. Overall, Cyclopoida and Daphnia were more abundant in the vegetated area, but Calanoida were more abundant in the non-vegetated areas. Size differences were also found, but differences were inconsistent among months and habitat classifications. We also quantified the number of samples required to obtain a 20% coefficient of variation of the mean abundance of zooplankton species among months and habitat categories. The results of our study illustrate the importance of implementing a sampling design that accounts for the spatial variation in zooplankton.