The samples were then stored at -20°C until treatment. A CTD (Rinko profiler, JFE Advantech, Tokyo, Japan) was attached to the base of the net frame to collect environmental data for each tow and a flow meter (RIGO Co. Ltd, Tokyo, Japan) attached to the opening of the net to record flow rate. GPS locations were taken at the start and end of every tow. At each location a blank net was taken for control by submerging the net briefly with a new bucket (~1 min).