A US-based environmental group on Wednesday expressed concern over new photos that seem to show the killing of large numbers of "biologically vulnerable" sharks by fishermen in Taiwan.

The Pew Environment Group posted several photos on its website showing dozens of gutted sharks being unloaded from trucks and lined up on the ground, as well as huge piles of fins on the floor of a warehouse.

"These images present a snapshot of the immense scale of shark-fishing operations and show the devastation resulting from the lack of science-based management of sharks," said Matt Rand, the group's shark specialist.

"Unfortunately, since there are no limits on the number of these animals that can be killed in the open ocean, this activity can continue unabated."

Taiwan announced plans in July to tighten measures against hunting sharks for their fins -- a delicacy in Chinese cuisine -- and have barred fishermen from tossing sharks back into the water to die after sawing their fins off.

A Pew report from January listed Taiwan as having the fourth largest number of reported shark catches in the world -- after Indonesia, India and Spain -- with the four accounting for more than 35 percent of the global total.

The group estimates that up to 73 million sharks are killed annually to support a global trade in fins, and has warned that the rapid depletion of shark populations threatens entire ocean ecosystems.

"This strip-mining of the world's sharks is clearly unsustainable, and governments need to act now if these predators are to swim the world's oceans in the future," said Rand.

The photos can be viewed at www.pewenvironment.org.