Conservationists say more than 200 Bottlenose dolphins are set to be slaughtered on Tuesday, as part of an annual hunt in Japan.
Fishermen corralled around 250 of the animals into a cove in Taiji three days ago, where many remain as they wait to be selected for a life in aquarium captivity or to be butchered for their meat.
On Monday The Sea Shepherd Conservation Society tweeted a total of 51 dolphins from the pod had been taken into captivity so far.
It adds the remaining 200 or so animals will spend a fourth night trapped without food and will be slaughtered on Tuesday.
The brutal selection process sees the scared and panicked animals throwing themselves onto rocks as fishermen cheer and trainers look on.
Meanwhile, in what is being described as an unusual move, the US Ambassador to Japan has expressed concern over the annual hunt, describing it as “inhumane”.
Caroline Kennedy tweeted in both Japanese and English, stating: “Deeply concerned by inhumanness of drive hunt dolphin killing.
“USG opposes drive hunt fisheries.”
The current pod is one of the largest to have been driven into the cove in several years, and Sea Shepherd has provided live streams and uploaded pictures to Facebook showing the distressed creatures swimming in circles in shallow waters.
The group is using the hashtag #tweetfortaiji to raise awareness on social networks.
Taiji on the south-west coast of Japan was made famous in 2009’s Academy Award-winning film The Cove, which documented the entire process from capture, to selection, to aftermath.
It was met with fierce opposition in Japan from groups saying it was "anti-Japanese" and an affront to traditional culture.
The country continues to maintain that the killing of dolphins is not banned under any international treaty, that the animals are not endangered, and that the culls are needed to protect fishing grounds.
Around 23,000 dolphins are slaughtered annually in the coastal village. Last year the town announced plans to open a marine park where visitors can swim with the mammals - as well as eat their meat - as the hunt continues nearby.
The ambitious plans could see a 28 hectare area netted off a the entrance of Moriura Bay.
Town official Masaki Wada said: "This is part of Taiji's long-term plan of making the whole town a park, where you can enjoy watching the marine mammals while tasting various marine products, including whale and dolphin meat."