After an immature mussel settles, it can remain attached to hard substrate for life. If conditions become unsuitable because of physical disturbance or poor water quality, zebra mussels can release from their byssal threads. Once detached from the substrate, single individuals can be carried passively to new structures where they can settle and secrete new byssal threads. Zebra mussels can also crawl by extending the foot tip, anchoring it to substrate with mucus, then contracting the muscles to pull the body forward. Small individuals are more mobile than large mussels.
The ability of zebra mussels to remain attached to boat hulls, woody vegetation, and trash is also responsible for their rapid dispersal. In addition, groups of byssal attached mussels can break loose from dense mats and infest new areas.