A mother dolphin tried desperately to save her calf from Japanese hunters who planned to sell the animals to aquariums, according to activists.
Heartbreaking footage of the incident was taken in Taiji, a coastal town in the Wakayama Prefecture.
The video, taken by volunteer Liz Carter, shows a group of divers trying to wrestle a dolphin away from its pod, Daily Mail reports.
When a diver grabs one of the dolphins, it tries to frantically wriggle its way out of the hunter's grasp.
A larger dolphin swims beside the hunters and tries to get them to let go of the calf.
The calf almost makes it back to its pod, but its dragged in the other direction by the group of hunters.
The men take the terrified dolphin back to their boat, where it is hauled up in a net.
While the hunters are rounding up the dolphins, a woman can be heard in the background saying: "Oh my god, the mother's trying to follow him."
Ms Carter, who volunteers with Blue Cove Days, wrote on Facebook: "Juveniles ripped from their mothers, this scene, the mother and child are desperately trying to stay together."
The activist claims that the animals are then sold to aquariums and marine parks in Japan.
She added: "The price of a ticket and a day trip out to a marine park isn't worth this."
The video has been watched by more than 1.5 million people, since it was published on January 21.
Hunters have taken part in the annual Taiji Dolphin Drive between September and March since 1969.
But, numbers of dolphins taken during the hunt have decreased over the last decade.
In 2004, around 1,600 dolphins were snatched and by the 2014/15 season, around 750 were taken, according to the International Marine Mammal Project (IMMP).
The controversial hunt was brought to light in the 2010 film The Cove, which documented Taiji fishermen hunting dolphins.
The hunters would then try to sell the animals to aquariums for as much as £123,000, according to IMMP.
But in May 2015, Japanese aquariums decided to stop buying dolphins from Taiji.