A Mexican fisherman has died after his vessel collided with a boat of the US conservation group Sea Shepherd in a sanctuary for the endangered vaquita porpoise, an official said Monday.

The fisherman was hospitalized on December 31 in the northwestern city of Mexicali with serious injuries including hip and pelvic fractures, regional health chief Alonso Perez told AFP.

A second fisherman is in a stable condition, he said.

According to the Mexican navy, the Sea Shepherd conservationists were collecting fishing nets in the Sea of Cortez "when they were attacked by fishermen with handmade explosive devices."

Sea Shepherd said that fishermen throwing Molotov cocktails attacked its vessels Farley Mowat and Sharpie, which were working with Mexican authorities to remove illegal nets.

It said that as the Farley Mowat tried to leave the area, one of the fishing boats "aggressively swerved" in front of the former US Coast Guard vessel, crashing into its hull and splitting in two.

The dead fisherman's family, however, accused the Sea Shepherd vessel of intentionally ramming his boat.

It issued a plea on social media that his death "does not go unpunished."

Sea Shepherd conservationists have been attacked on a number of occasions while patrolling the vaquita marina refuge that Mexico has established in the Gulf of California.

The world's smallest species of porpoise, the vaquita has been pushed to the brink of extinction by illegal fishing, according to the International Union for Conservation of Nature.

The porpoise gets entangled in illegal gillnets used to catch the endangered totoaba fish, whose swim bladder is highly prized in parts of Asia, the IUCN says.

The vaquita is only found in the Gulf of California, whose islands and protected areas became a UNESCO World Heritage site in 2005.

In 2019 the World Heritage Committee decided to add them to the World Heritage in Danger list due to fears of the imminent extinction of the vaquita.

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