Twenty dolphins were slaughtered as the annual Taiji dolphin hunt in the south of Japan began on Friday. The hunt has earned worldwide attention after the controversial documentary, "The Cove," was released in 2009.

According to a news release from Agence France-Press via The Guardian, during the six-month hunting season this year, local fishermen from Taiji plan to kill 1,820 dolphins -- the 20 dolphins were the first victim of this gruesome hunt.

"For several days the hunters have been pursuing pods offshore, who were able to escape capture. This pod of Risso's dolphins was not so lucky. The senseless slaughter of the adult dolphins, while forcing the young to fend for themselves in the open sea, should serve as a call to action for everyone," Ric O'Barry, the founder of the Dolphin Project and proprietor of "The Cove" documentary, told National Geographic in an email.

The six-long Taiji hunt will run from September 2016 to March 2017. One hundred fifty live bottlenose dolphins have also been pre-sold to marine parks while trainers will get the chance to choose who to get for captivity.

Meanwhile, environmental organizations and advocates have expressed their concern regarding the controversial Taiji dolphin hunt. Some of them have even visited the local town of Taiji to show their protest, but Japanese authorities have also boosted their numbers to prevent any clashes between animal rights advocates and local hunters. 

To recall, "The Cove" documentary in 2009 exposed this gruesome dolphin slaughter that most of Japan and the world don't know about. The film shows local fishermen drawing dolphins to the shore of a secret cove using nets and stress sounds, where they are stabbed and pierced, turning the blue sea to blood red. 

“The killing of dolphins is indefensible given our scientific knowledge of dolphins, which has demonstrated their sophisticated cognitive abilities including self and social awareness,” Diana Reiss, a psychologist from Hunter College, told New Scientist in 2013.

Kris Simpson of International Dolphin Watch also expressed the same concern, saying that dolphins must not be hunted and should " receive the highest standards of treatment in any hunt, equal to that granted to domestic animals."

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