Chinese fishing companies are engaged in systematic pillaging of west African fisheries on a huge scale, according to a new report from Greenpeace, which also accuses the companies of taking advantage of weak and chaotic governance resulting from last year’s Ebola outbreak in the region.

A two-year investigation by the environmental group found that four Chinese fishing companies, including state-owned China National Fisheries Corporation, carried out persistent “illegal, unreported and unregulated fishing activities and gross tonnage fraud in west Africa.

In just the latest cases, the Greenpeace ship MY Esperanza documented 16 illegal fishing activities by 12 Chinese vessels in Guinea’s exclusive economic zone in October and November last year, while the Ebola outbreak was raging and countries in the region were unable to monitor their waters.

“While China extended a hand in friendship during the Ebola outbreak, rogue Chinese companies were unlawfully exploiting west Africa’s marine environment, 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 jeopardise what the Chinese government calls its mutually beneficial partnership with west Africa.

The number of Chinese fishing vessels in Africa has grown from just 13 in 1985 to 462 in 2013, accounting for a fifth of China’s entire long-range fishing fleet, and Greenpeace says Chinese companies are the worst offenders when it comes to illegal fishing in the region.

As well as fishing in prohibited areas, Chinese fishing companies systematically under-declare the gross tonnage of their vessels, allowing them to evade licensing fees and operate in areas where large boats are forbidden.

The majority of these boats are bottom trawlers, which use one of the most destructive fishing techniques.

Ironically, China is taking steps to eliminate some of the most environmentally damaging fishing practices in its own waters.

Faced with more competition and stricter rules at home, Chinese fishing companies are looking further afield. The lack of rigorous fisheries management and enforcement in west Africa has made it an attractive destination for large Chinese companies with the resources to send boats to distant waters.

“If China wants to be a genuine friend of Africa, it should follow the path of the European Union’s Common Fisheries Policy, which is slowly rectifying the EU’s own history of irresponsible fishing in the region, said Ahmed Diame, Greenpeace Africa Ocean Campaigner.

China’s Ministry of Agriculture, which regulates Chinese fishing at home and abroad, and China National Fisheries Corp, the largest of the four Chinese companies identified in the Greenpeace report, declined to comment.

“That is nonsense, what evidence do they have? This sort of thing is rare, the controls are strict and there could be sanctions, said Zhang Hua, general manager of Dalian Bo Yuan Overseas Fishing Corp, one of the four companies named in the voluminous Greenpeace report, which included detailed evidence and records of their illegal fishing activity.

Two other companies, Dalian Lian Run and Shandong Overseas Fisheries Development, could not be reached for comment but Dalian Lian Run was punished by China’s Ministry of Agriculture in July 2013 for illegal fishing activities in Guinea.

The Financial Times Ltd 2015