Settled juvenile zebra mussels can grow between 5 and 20 mm within their first year of life depending upon the conditions of their habitat (particularly temperature and food). Under the best conditions, they are capable of growing up to 0.2 mm/day.
The life cycle of the zebra mussel
Aside from recording the location of the sample of settled juveniles, the date, the time, and the sample number, it is important to record the habitat conditions that existed when the sample was taken. Specific conditions may exist at one site that are conducive to high zebra mussel growth rates, but they may not exist at another site within the same facility. These favorable conditions for zebra mussel growth will likely lead to higher mussel biomass in these areas.
The size of the mussels can be recorded in several ways, including direct measurements of mussel dimensions (length, width, etc.) or measurement with the displacement method as described by Marsden (1992). Growth rates can be determined over time from such measurements.
Importance of Maintaining Long-Term Records of Monitoring Data