The predation of zooplankton by the blue mussel (Mytilus edulis) and the clubbed tunicate (Styela clava)

Consumption of planktonic larvae of bivalves, copepods, gastropods and polychaetes by
Mytilus edulis and Styela clava was evaluated in the laboratory. Two experimental groups
of filter feeders were compared: 1 M. edulis and 1 S. clava. Clearance rates of all prey
taxa were similar for M. edulis and S. clava. Ingestion rates (IR) were not different
between the two predators except for one occasion when M. edulis had higher IR of
copepods. Clearance rates of the different prey taxa were not different for either predator
species. Mussels and tunicates both consume larvae. However, the abundance of tunicates
in certain areas of PEI may increase the predation pressure on larvae which may decrease
mussel larvae collection. Also, tunicates may reduce the food available to mussels which
might, in turn reduce their reproductive potential.