Ingestion of Lepeophtheirus salmonis by the blue mussel Mytilus edulis

Integrated multi-trophic aquaculture (IMTA) is an exciting alternative approach to mono-culture aquaculture that reduces environmental impacts of commercial aquaculture systems by combining the cultivation of fed aquaculture species (finfish) with extractive aquaculture species (e.g., shellfish and seaweed). This increases the sustainability and profitability of finfish culture as the organic particulate wastes can be removed by the shellfish extractive component and dissolved inorganic nutrients are extracted by the seaweed component. Shellfish play a critical role in an IMTA system by extracting particulate bound organic nutrients; however they may also influence pathogen dynamics by serving as a reservoir or as a barrier for finfish pathogens, depending on pathogen physiologies. The sea louse, Lepeophtheirus salmonis, has recently made a spectacular comeback as a major parasitic pest of farmed Atlantic salmon (Salmo salar L.) in the Northeast of the United States. The re-emergence of this parasite is due to development of louse resistance to SLICE™, the drug of choice for treating L. salmonis infestations over the last decade. Incorporation of mussel crops on salmon farms may be an alternative method to reduce the infectious pressure of sea lice on farms if mussels can consume copepodids, the planktonic and infectious stage of sea lice. Our study demonstrated that mussels can remove copepodids from the water column. Individual mussels were exposed to copepodids (200 copepodids l−1) for 30- and 60-min durations. Copepodids were observed in the buccal cavity and in stomach contents. Molecular analyses confirmed the presence of copepodids in mussel stomach contents.