Using the data obtained from the twice-weekly plankton sampling, it can roughly be determined when the zebra mussels will settle. From the time of peak veliger density, it can take between 3 and 5 weeks for the veligers to become settling juveniles. As this occurs, the veligers' growth renders them too heavy to remain free-swimming in the water column, and they begin to settle to the bottom. Once settled, they move using their foot until they have found a suitable substrate on which to attach using tough fibers called byssal threads. The use of settlement samplers with coupons will help to detect these initial settling mussels - the pediveliger stage.
Zebra mussels will settle upon virtually any hard substrate
Once settled, zebra mussels colonize and form druses of mussels
Zebra mussels attach to substrates with byssal threads
Juveniles will settle on almost any substrate, but exhibit preferences relating to substrate texture, ionic concentrations, water velocity, water depth, temperature, and light. Juveniles also prefer to settle close to other colonized mussels, in cracks or crevices, or along the edges of a substrate. Settled juveniles are able to move about on their foot at an average rate of 3 cm/hr in order to find a more suitable location upon which to attach. Once the settled juveniles have attached using byssal threads, it does not mean that they will remain fixed to that substrate, as they are capable of detaching and relocating.
Importance of Maintaining Long-Term Records of Monitoring Data