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

A wall jet is presented as a novel means of measuring the attachment s trength of zebra mussels. Attachment strength was inferred from a flui d 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 bugensi s (approximate to 8-10 mm long), the mean (+/-SE) DP was 8.9 +/- 0.9 m Pa . m(2) on limestone/dolomite, 5.6 +/- 0.5 mPa . m(2) on polyvinylch loride, 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 a ntigrades; <1 mm) was two orders of magnitude less than adult mussels. These results were validated with conventional tensile loadings, in w hich 633 Dreissena bugensis and 26 Dreissena polymorpha were pulled of f substrates with a calibrated force scale. The tensile loadings resul ts were comparable with those of marine bivalves. Good correlation bet ween pull-off force and DP was observed. Information of this nature is useful for the implementation of environmentally benign zebra mussel controls.