Marine zoning could be bigeye tuna’s lifeline
Marine zoning in the Pacific Ocean, in combination with other measures, could significantly improve dwindling numbers of heavily overfished bigeye tuna and improve local economies, a fish modeling study has found.
Scientists from the University of Hawaii, the Secretariat of the Pacific Community (SPC) and Collecte Localisation Satellites have found that a network of marine zones in the Pacific Ocean could be a more effective conservation measure than closing relatively small areas to certain types of fishing. The findings are published in the 30 October edition of the Proceedings of the National Academy of Sciences.
Dr. John Hampton, of the Oceanic Fisheries Programme of the SPC, is one of four scientists leading the study. After testing the effectiveness of a range of conservation measures with an ecosystem and fish population model, Hampton said the team found that the most efficient measures were to restrict longline fishing in tuna-spawning areas and to restrict the use of fish-aggregating devices (FADs) in areas where purse-seine nets are being used.
“We found that simply closing areas off to fishing doesn’t work, because the boats just move their operations to neighboring zones and chase fish even harder. It’s going to need a combination of approaches,” said Hampton.
The study calls for a complete economic valuation of the Western Central Pacific Ocean tuna fishery.
“The model will help people evaluate different ways of managing tropical tuna fisheries. Our predictions can help countries estimate how effective conservation measures might be, relative to any economic effects, and tailor measures to suit their goals. The advantage of this approach is that effects can be estimated locally, as well as for the stock as a whole,” said Hampton.
Half the bigeye tuna harvested by longline, which targets high-value tuna sold as fresh fish, sells for more than USD10 (EUR7.86) per kilogram. The other half is harvested with purse-seine nets as incidental catch during skipjack tuna harvests. These juvenile bigeye tuna are sold to the canning industry for USD$1.70 (EUR1.34) per kilogram.
Rebuilding the bigeye-tuna stock will take at least 15 years, and will be affected by any climate changes the ecosystems experience, the study said.
The Spatial Ecosystem and Population Dynamics Model the researchers used was developed with support from a series of European Union–funded projects implemented by the Oceanic Fisheries Programme of the SPC, the National Oceanic and Atmospheric Administration–funded Pelagic Fisheries Research Program at the University of Hawaii and CLS.