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Comparison of Zebra Mussel Veliger Laboratory Enumeration and Sampling Techniques

Zebra mussel (Dreissena polymorpha) invasion greatly impacts aquatic systems, with economic and ecological consequences. Monitoring zebra mussel density and reproductive timing are essential for effective detection, management, and control of this invasive species. Veligers, the free-floating planktonic life stage of zebra mussels, are often monitored to estimate reproductive effort and as a first indicator of zebra mussel invasion. Although many veliger monitoring methods exist and vary greatly in cost and effort, no study has compared results yielded by different sampling techniques. We compared estimated veliger densities collected with offshore vertical plankton net tows and oblique plankton net tows taken from shore from April through October 2011 in Marion Reservoir, Kansas. Secondarily, we compared enumeration results returned by an established laboratory and a laboratory that had recently begun enumerating veligers. Using ANOVA testing, we found no significant difference between sampling methods or laboratories. We recommend using oblique plankton net tows taken from shore because of their potential to reduce monitoring costs compared to other sampling techniques by reducing equipment, time, and manpower expenses.