According to the environmental activist group Greenpeace, the Nisshin Maru left the Innoshima port near Hiroshima on Monday. The rest of the fleet is scheduled to leave from another port later this month.

The Japanese government, in order to avoid protests, would not confirm that the vessel had left and decided not to hold a departure ceremony to see the boat off. But Greenpeace members were there at the port, with a banner that read, “Whaling on Trial.”

Last year, protesters from the animal rights organization, Sea Shepherd Conservation Society, caused the Japanese fleet to return home early. A Sea Shepherd vessel collided twice with a whaling ship, and activists were also accused of boarding a whaling vessel and unloading acid, injuring two crew members. Two of the protesters were detained by the Japanese government, which accused Sea Shepherd of engaging in an “act of piracy.”

Whale meat has been a popular delicacy in Japan for centuries, although demand has been declining in recent years.