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In the process of developing a fish aggregating device (FAD) for reducing the entanglement of bycatch, the flows that occur in both existing high-risk net-type entangling FADs and low-risk rope-type FADs equipped with non-entangling cloth attractors were measured using a flow visualization technique. At an inlet velocity of 0.504 m/s, the mean velocity data for net and rope FADs were 0.525 m/s and 0.280 m/s, respectively, and the turbulence intensity data were measured as 10.8% and 46.9%, respectively. The mean velocity data for the rope FAD and spindle-type fish were 0.126 m/s and 0.164 m/s, respectively, and the turbulence intensity data were 37.0% and 17.9% respectively, at an inlet velocity of 0.2 m/s. For the measurement and analysis of the flow data, the particle image velocimetry method was used. The flow velocity and turbulence intensity data revealed that compared to existing net-type entangling FADs, rope-type FADs equipped with ribbons had a significantly larger or smaller difference in the velocity and turbulence intensity compared to the surrounding flow rate.
