Daily Settlement Rates of the Zebra Mussel, <i>Dreissena polymorpha</i>, on an Artificial Substrate Correlate with Veliger Abundance

Abstract

The relationship between daily settlement rates and local concentrations of veligers of the zebra mussel, Dreissena polymorpha, was investigated using plankton sampling and scouring pad collectors. A total of 102 plankton and 136 collector samples were taken from a nearshore site near Wheatley, Ontario, in west-central Lake Erie, over 17 consecutive d in August 1992. Results demonstrate a strong correlation between daily settlement rates and daily concentrations of late-stage (competent) veligers in the water column (determined at shell lengths ≥ 170 μm; r = 0.93–0.98; p &lt; 0.001; log 10 -transformed data). Variations in settlement rates of 1–3 orders of magnitude occurred within 24–96 h. Results also suggest that wind-induced hydrodynamics can affect settlement rates of zebra mussel larvae; the period used to monitor settlement (24 h) was much shorter than that employed (~1–2+ wk) in previous studies. Daily monitoring of concentrations of late-stage veligers in the water column as well as settlers (fibrous collectors) may help to identify biological and physical factors affecting short-term variability in settlement; it may also prove advantageous for industries where early detection of colonization by the zebra mussel is critical for cost-effective control of this invasive mollusc.