Chinese companies have been fishing illegally off the coast of West Africa, at times sending incorrect location data suggesting they are as far away as Mexico or even on land, the environmental group Greenpeace said in a study released on Wednesday, .

The report alleges that Chinese fishing vessels took advantage of the chaos caused by the 2014 outbreak of Ebola, which hit Liberia, Guinea, Sierra Leone and several other West African countries, to conduct illicit fishing trips.

“Not only are they exporting the destructive fishing model that destroyed China’s own fisheries, but some irresponsible Chinese companies were stealing fish from African countries affected by Ebola outbreak as its government was conducting one of the biggest aid programmes to support these African countries to confront a major local public health crisis,” the report states.

The number of Chinese-flagged or Chinese-owned fishing boats operating in Africa has soared in recent decades, from just 13 in 1985 to 462 in 2013, Greenpeace said.

Greenpeace said it found 114 cases of illegal fishing by such vessels in periods totaling eight years in the waters off Gambia, Guinea, Guinea-Bissau, Mauritania, Senegal and Sierra Leone. The boats were mainly operating without licenses or in prohibited areas.

Among them, 60 cases involved vessels of the China National Fisheries Corporation (CNFC), a state-owned company charged with developing fishing in distant seas.

The Chinese excursions into West Africa come as Beijing has started trying to better regulate its own fishing policy, according to the Financial Times.

“While the Chinese government is starting to eliminate some of the most destructive fishing practices in its own waters, the loopholes in existing policies lead to a double standard in Africa,” Ahmed Diame, a Greenpeace Africa ocean campaigner, said in a statement.

The cases were reported by the Surveillance Operations Coordination Unit of the Dakar-based Sub-Regional Fisheries Commission, various national lists of infractions, and by Greenpeace itself, the study said.

A Greenpeace ship found 16 cases of illegal fishing by 12 Chinese-flagged or Chinese-owned vessels in one month last year, the group said. Some of the ships Greenpeace observed were reporting incorrect Automatic Identification System information, the group added.

The CNFC under-reported gross tonnage for 44 of its 59 vessels operating in West Africa, the report alleged, a practice that enables companies to evade licensing fees and could potentially mean they were fishing in prohibited areas.

The Chinese ships were “taking advantage of weak enforcement and supervision from local and Chinese authorities to the detriment of local fishermen and the environment,” said Rashid Kang, head of Greenpeace East Asia's China ocean campaign.

“Unless the government reins in this element of rogue companies, they will seriously jeopardize what the Chinese government calls its mutually-beneficial partnership with West Africa,” he added.

But one Chinese fishing company mentioned in the report rejected the Greenpeace's accusations.

“That is nonsense. What evidence do they have?” Zhang Hua, head of Dalian Bo Yaun Overseas Fishery, told the Financial Times. Greenpeace identified Zhang's company as one of the alleged violators of fishing rules.

“This sort of thing is rare, the controls are strict, and there could be sanctions,” Zhang added.

Chinese companies are increasingly looking abroad for resources, including fish.

Fishing resources are also an element of the competing territorial claims in the South China Sea, which Beijing claims almost in its entirety. China has clashed with Vietnamese and Filipino fishing ships in the region, sometimes boarding vessels or chasing them off with water cannon.

Al Jazeera and Agence France-Presse