A WALL-JET TO MEASURE THE ATTACHMENT STRENGTH OF ZEBRA MUSSELS

A wall jet is presented as a novel means of measuring the attachment strength of zebra mussels. Attachment strength was inferred from a fluid detachment parameter (DP), defined as the nominal wall shear stress at the detachment site X mussel length(2). DP varied significantly on natural and artificial substrates: in tears with 288 Dreissena bugensis (approximate to 8-10 mm long), the mean (+/-SE) DP was 8.9 +/- 0.9 mPa . m(2) on limestone/dolomite, 5.6 +/- 0.5 mPa . m(2) on polyvinylchloride, 4.3 +/- 0.4 mPa . m(2) on stainless steel, 4.2 +/- 0.5 mPa . m(2) on aluminum, and 2.5 +/- 0.3 mPa . m(2) on polymethylmethacrylate (Plexiglas). The attachment strength of postlarval mussels (pl Alpha antigrades; <1 mm) was two orders of magnitude less than adult mussels. These results were validated with conventional tensile loadings, in which 633 Dreissena bugensis and 26 Dreissena polymorpha were pulled off substrates with a calibrated force scale. The tensile loadings results were comparable with those of marine bivalves. Good correlation between pull-off force and DP was observed. Information of this nature is useful for the implementation of environmentally benign zebra mussel controls.