The dreissenid musselMytilopsis sallei (Recluz) settles on man made structures in confined harbour waters. The mussel unlike some mytilids is never found to have settled on coastal sea bed. It shows a good capacity to produce a byssus apparatus and develops a new one every time it settles afresh. Younger mussels develop byssus apparatus at shorter intervals and therefore move more often. Adults are relatively passive. Byssal thread development is influenced by the environmental factors and also by the quality of surface. The mussel achieves better adhesion on polar surfaces like slate and glass than on teflon. Tensile strength of adhesive threads is very poor as compared to other mytilids. This possibly is one of the reasons for its absence on sea beds where sea water turbulence is very high.