The World Wildlife Fund conservation group has accused organisations set up to control deep-sea fishing of failing to protect fish stocks.
In a report it said overfishing in international waters was driving some species – including tuna – to the verge of extinction.
The WWF urged governments to clamp down on “pirate fishing”.
But it said even if this stopped, fish numbers would still decline owing to poor management of global resources.
BBC science reporter Matt McGrath says that on the high seas – away from the protection of national quotas – fish stocks are at their most vulnerable.
Stocks of some deep-sea species, such as the orange roughy, have collapsed as regulators failed to respond to the expansion of bottom-trawling in deep waters.
The regulation of fishing in these international waters is the responsibility of regional fishing management organisations – made up of countries with a vested interest in the area.
According to the WWF, most are failing to manage fish stocks in a sustainable way.
Decision-making is poor, it says, and the regional organisations are powerless to control the activities of countries who ignore regulations.
The report cites illegal fishing “by highly mobile fleets under the control of multinational companies” as one of the top threats to marine life.
The authors are calling on the United Nations to review fishing on the high seas and strengthen the resolve of regional authorities to deal with states that flout agreements.
“Given the perilous overall state of marine fisheries resources and the continuing threats posed to the marine environment from overfishing… the need for action is immediate,” said Simon Cripps, director of the WWF’s global marine programme.
Source: BBC Online