Treatments to eradicate invasive tunicate fouling from blue mussel seed and aquaculture socks

Tunicates can foul blue mussels and negatively affect productivity on mussel farms. In New England and elsewhere, invasive species of colonial tunicates commonly foul wild and cultured blue mussels and aquaculture gear. Eco-friendly experimental treatments that meet industry guidelines were selected for trial application. Chemical (acetic acid) and water (brine and freshwater) treatments were applied in short-term and long-term applications to juvenile mussels that either were or were not exposed to tunicates. Acetic acid baths (5 mins and 10 mins) were lethal to juvenile mussels. Brine baths killed tunicates, but caused relatively high mussel mortality, though less mussel death occurred in the short-term (10 sec) brine bath (6-17%) compared to the long-term (20 sec) brine bath (8-30%). Both long-term (24 hr) and short-term (8 hr) freshwater baths were effective against tunicates, with less mussel mortality (2%) occurring in the short-term bath. Tunicates survived short-term freshwater sprays but not long-term freshwater sprays. Long-term (10 mins) freshwater sprays caused slightly more mussel mortality (4%) than short-term (5 mins) freshwater sprays. Each treatment demonstrated varying degrees of effectiveness, yet the freshwater short-term baths and sprays were able to remove tunicates while maintaining high survivorship among juvenile mussels. Additionally, freshwater treatments do not require the use or disposal of chemicals.