BEIJING - As ConocoPhillips and China's ocean watchdog try to control the spread of oil leaks in a gulf of the Yellow Sea, fishers in North China's Hebei province are complaining that the disaster has caused the death of a large number of scallops.

"Because of the leak, about 70 percent of the scallops seedlings in Laoting county (Hebei province) have been found dead since late June, and the total economic loss for the local fishing industry is expected to reach 350 million yuan ($54 million)," Yang Jizhen, chairman of the Laoting fisheries association, told China Daily on Monday.

The recent oil leak in Bohai Bay was first discovered on June 4 and a subsequent one was learned of on 17. Both originated from the bay's Penglai 19-3 oilfield.

Since then, the substance has been found ashore in northern Hebei province and northeastern Liaoning province, according to a notice released by the North China Sea branch of the State Oceanic Administration on July 19.

Many people say they believe the leak has inflicted great harm on the environment.

Yang said he plans to join forces with local fishers in filing a lawsuit against ConocoPhillips, the operator of the oilfield where the leak originated, and its partner, China National Offshore Oil Corp.

About 160 households in Laoting county rely on fishing and related work for their livelihoods, according to statistics from the association.

A deputy director for the Laoting aquatic product bureau surnamed Qi confirmed that scallops had indeed died, but "the question of whether the deaths were caused directly by the leak is still being investigated," he said.

Qi asked the State Oceanic Administration to take test samples in Hebei province to learn if a connection exists between the leak and the deaths.

"Scallops are very sensitive to their environment in the water," he said. "Although dead scallops are found every year, they are seldom found in such great numbers."

Zhai Yuxiu, deputy director of the National Center for Quality Supervision and the Testing of Aquatic Products, said the public will only be able to know if the oil leak was related to the deaths after authorities have released the results of testing. Often the causes of such incidents, he explained, are numerous and complicated.

The leak has polluted about 4,240 square kilometers of Bohai Bay, according to monitoring data released by the State Oceanic Administration on July 11.

The company has given the public little information about the cause of the leak and its potential effects on the environment.

Ma Jun, director of the Institute of Public and Environmental Affairs, criticized ConocoPhillips for "hiding the truth from the public" and called on the company to release a comprehensive report as soon as possible. By doing so, he hoped the company could help to prevent further economic losses and environmental harm.

ConocoPhillips, an energy company based in Houston, has estimated that from 1,500 barrels of oil to 2,000 barrels and oil-based drilling fluids have seeped into the sea from the Penglai 19-3 oilfield in Bohai Bay.

The State Oceanic Administration ordered the company to shut down production at two of the oilfield's platforms on July 13.

Cui Wenlin, director of the North China Sea Environment Monitoring Center, said on Monday that the leak has already been diluted in the vast sea. He said tests will be conducted every 10 days to determine the quality of the water in the bay.