Evaluation of treatments to reduce the spread of a marine plant pest with aquaculture transfers

Removing Undaria from mussel seed-stock is more problematical because of the importance of identifying treatment conditions that do not compromise mussel health. Mussels were not adversely affected when immersed in freshwater for a 2 day duration sufficient to ensure complete Undaria mortality. Hence, mussels could potentially be treated in freshwater at reasonable cost while being transported between aquaculture regions. However, to ensure an effective treatment the water would need to be exchanged during the transport phase in order to maintain salinities at ≤ 1 psu. Our findings also suggested that exposure to hot water at 55 °C for approximately 5 s would achieve complete Undaria mortality while maintaining a level of mussel survival comparable to untreated seed-stock. This method is likely to involve greater costs than freshwater immersion, and requires field validation to confirm both the efficacy against Undaria and to identify a method of implementation that ensures mussel survival is not compromised by the combined stresses of treatment and inter-regional transport.