Biologists attach cables to concrete devices, known as mussel silos, and place them on the bottom of the Cedar River. 

The mussel silos have an opening in the bottom where juvenile mussels are kept in cylindrical chambers (see the next photo).  The vent at the top allows water to circulate through the chamber.  We used a common mussel species (fat mucket - Lampsilis siliquoidea) for this biomonitoring project. 

These fat mucket mussels are about one year old.  They were artificially propagated at the Genoa National Fish Hatchery in Wisconsin. 

The silos with young mussels were placed in the river early in the summer.  Mussels are kept in the silos on the river substrate to late autumn. 

A set of mussel silos were placed above a major city and another set is place below the city to determine whether any changes in survival or growth are related to urban pollution or just the pollution common to all reaches of the river. 

After placing the mussels silos in the Cedar River, biologists periodically inspected them to check on their status, document mortality, and measure growth of each mussel. 

After a few weeks, it became clear that mussel silos placed on a gravelly shoal were in an area of heavy sedimentation. Sand and silt transported along the river bottom were pulled up into the silo chambers and smothered the mussels. 

Mussel silos placed on rocky substrates did not experience sedimentation. Water circulated well in the chambers and the mussels survived.

Data from the 2011 Cedar River biomonitoring