Jeju – Global tuna stocks are fast reaching the limits of fishing sustainability, decimated by an absence of comprehensive, science-based catch limits, conservation experts warned on Saturday.Overfishing pushing tuna to the brink

Five of the world’s eight tuna species are already classified as threatened or nearly threatened with extinction, according to the Red List of Threatened Species compiled by the International Union for Conservation of Nature (IUCN).

At the IUCN’s World Conservation Congress currently underway in South Korea’s southern Jeju Island, experts said partial quotas currently in place were inadequate and uninformed.

“The problem is, there is lack of science-based catch limits to ensure effective management and conservation,” said Amanda Nickson, Director of Global Tuna Conservation at the Pew Environment Group.

The five Regional Fisheries Management Organisations (RFMOs) that manage the global tuna fishing industry do have some measures in place, including restricting the catch of certain species to the amount caught in a previously defined year.

They also operate “input controls” that, among other things, limit the number of fishing vessels, but Nickson argued these were ineffective as they simply provided an incentive to develop more effective fishing methods.

While acknowledging that scientific data on tuna stocks was “imperfect”, Nickson said the UN Fish Stocks Agreement specifically provided for the setting of catch limits if the evidence in favour was compelling enough.

“There is sufficient science available to set precautionary limits,” Nickson said.

“If we wait five, 10 years for the science to be perfect, in the case of some species we may not have anything left to manage,” she added.

The Atlantic bluefin species, which can live to 40 years old and grow to more than 4m long, is in the gravest danger of disappearing with stocks estimated in some areas to have halved over four decades.

It is so highly prized by sushi-loving Japanese that a 269kg fish went for a record $737 000 (at the time) in January auctions.

“The message is that some tuna species are in bad shape,” said Bruce Collette, chair of the IUCN Tuna and Billfish Specialist Group.

“Long living and high value tunas are threatened by over exploitation and under regulation by the regional agencies,” Collette warned.

The global tuna industry is an economic juggernaut, with fishing in the Pacific Ocean alone – accounting for 65%of the global commercial catch – worth around $5.5bn a year.

Toshio Katsukawa, a fisheries expert from Mie University in Japan, said only urgent international cooperation could safeguard the future of the Pacific bluefin tuna.

“Immediate action is necessary” because the risk of commercial extinction is immediate, Katsukawa said.