The capture of an unusual dolphin with an extra set of fins is shedding light on a controversial hunting technique in Japan.

The bottlenose dolphin was captured alive on October 28 during Japan’s annual dolphin “drive hunt.”

During the hunt, fishers use boats and loud noises to herd hundreds of dolphins into shallow bays. There, many are corralled into nets and killed. Others are kept live and sold to aquariums, according to conservationists.