Filtration of sea louse, L epeophtheirus salmonis , copepodids by the blue mussel, M ytilus edulis , and the A tlantic sea scallop, P lacopecten magellanicus , under different flow, light and copepodid‐density regimes

Population management of L epeophtheirus salmonis in C anada currently relies on chemotherapeutants to remove attached stages of the ectoparasite. However, some populations of L . salmonis are developing resistance to chemotherapeutants making alternate management measures necessary. This article explores the ability of filter‐feeding shellfish [ i.e . blue mussels ( Mytilus edulis ) and A tlantic sea scallops ( P lacopecten magellanicus )] to consume the copepodid stages of L . salmonis in the laboratory under static and flowing water conditions, with variable copepodid densities, and with the aid of a light attractant. M ytilus edulis consumed copepodids under both static and flowing water conditions, and the proportion of individuals ingested was similar at low and high copepodid densities, suggesting that M . edulis was not saturated at the concentrations tested. Also, M . edulis consumed more copepodids when a light attractant was present, suggesting that lights may be useful to concentrate widely dispersed copepodids around cultured shellfish in the field. Finally, P . magellanicus consumed the same number of copepodids as an equivalent total wet weight of M . edulis . During each of the four separate experiments, shellfish consumed between 18 and 38% of the copepodids presented per hour, suggesting that both species are well suited for low level removal of copepodids over time.