Collapse feared for tuna fishery
A major South Pacific tuna fishery exploited by New Zealand commercial and recreational boats is on the verge of collapse, experts say.
South Pacific stocks of bigeye tuna (Thunnus obesus) were just 20 per cent of what they would have been if left unfished, which scientists with the Secretariat of the Pacific Community (SPC) called an unacceptable risk.
Current catches are exceeding bigeye tuna's maximum sustainable yield, and unless hard political decisions are taken there could be a species collapse akin to that of North Atlantic cod.
Hundreds of fishing boats, mostly Chinese but including 11 New Zealand flagged vessels, were scooping up adult bigeye that get high prices on Japan's sashimi market. Juveniles, usually taken as bycatch in skipjack tuna fishing, were used in the low-value canning industry.
The fate of bigeye tuna will be decided at a meeting of the Western and Central Pacific Fisheries Commission (WCPFC) in the Marshall Islands next month.
SPC Oceanic Fisheries Programme head John Hampton said a drop below 20 per cent was significant.
"The WCPFC should now take firm action to reduce catches of bigeye and allow the stock to rebuild," he said.
The organisation had struggled to curb the growing tuna fleet.
"If we want a train wreck instead of a sustainable fishery, we should keep going the way we are now," said WCPFC's outgoing executive director, Glenn Hurry, earlier this month.
Shelton Harley, who co-ordinated the scientific team undertaking the assessments, said the data was the result of incorporating over 60 years of fisheries and biological data across the region.
"We had 40 computers running night and day for three months to complete the work."
Bigeye tuna is covered by New Zealand's quota system and is fished around the northern and eastern exclusive economic zones. Around $10 million worth of bigeye passes through New Zealand ports, not all of it fished within the EEZ.
If caught recreationally, it cannot be sold.
Several large bigeye catches have been taken recently. Earlier this year, Paihia woman Jo Henwood caught a 132.8 kg bigeye north east of Cape Karikari, and last year Gisborne's Julie Dowsing caught a 102.25 kg bigeye off Poverty Bay.
The SPC said the situation for the other tuna species, skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares), was brighter.
Skipjack, which accounted for 68 per cent of the total tuna catch in 2013, is estimated to remain at around 50 per cent of unexploited levels.
That was regarded as desirable.
Yellowfin was reduced to about 38 per cent of unexploited levels.
"While skipjack and yellowfin populations are currently okay, catches are likely at their full potential," Harley said.
He warned that more, larger fishing boats were joining the chase and stock levels were falling.
"Some urgent decisions are required on limits and their allocation."