The 12 were arrested at the Tubbataha Reef, a marine sanctuary in the western Philippines famed as a pristine dive spot, in April last year after their 48-metre (157-foot) boat hit and badly damaged it.
"The court imposed the maximum punishment of 12 years in prison for the boat captain," Hazel Alaska, clerk of the court that heard the case in the western city of Puerto Princesa said.
The written verdict identified the boat captain as Liu Chiangjie.
Regional trial court judge Ambrosio de Luna also fined the fishermen USD 100,000 each, while their boat was forfeited, Alaska added.
More From This Section
They were the first foreigners to be found guilty of violating the law, according to Herminia Caabay, legal officer for a council that helps the western province of Palawan protect its natural resources.
The fishermen are still on trial for possession of protected species within the park, Alaska said, a crime punishable by up to 20 years in prison.
Pangolins are widely hunted in parts of Asia, including Palawan, for their meat, skin and scales.
In China they are considered a delicacy and to have medicinal qualities.
The 12, who pleaded not guilty to all charges, are among dozens of Chinese and Vietnamese fishermen who are detained in Palawan for illegal fishing.
Among the others are nine Chinese fishermen who were arrested on May 6 off Half Moon Shoal, a South China Sea outcrop claimed by both China and the Philippines.
It requires long sailing in Philippine waters to reach.