14 November, 2012, NSJ
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 modelling study has found.
Scientists working at the University of Hawaii, the Secretariat of the Pacific Community (SPC) and Collecte Localisation Satellites (CLS) have found that a network of marine zones in the Pacific Ocean could be a [frax09alpha]more effective conservation measure than simply closing relatively small areas to some types of fishing.
These marine zones, where different fishing activities are allowed in different areas, may have significant and widespread benefits for bigeye tuna numbers.
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, Dr Hampton says the team found that the most efficient measures were to restrict:
· longline fishing in tuna-spawning areas
· the use of fish-aggregating devices (e.g. moored or drifting buoys which attract fish) in areas where boats use purse-seine nets.
“We found that simply closing areas off to fishing doesn’t work, because the boats just move their operations to neighbouring zones and chase fish even harder. It’s going to need a combination of approaches,” he says.
“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.”
Half the current bigeye tuna catch is by the longline method, which targets high-value tuna sold as fresh fish. This commands a market premium and sells for over $10 per kilogram.
The other half is caught in purse-seine nets as incidental catch when aiming to catch skipjack tuna. These juvenile bigeye tuna are sold to the canning industry for $1.70 per kilogram.
Dr Hampton says the study calls for a complete economic valuation of the Western Central Pacific Ocean tuna fishery.
He says the most important thing is that fish are protected throughout their lifetime.
Rebuilding the bigeye-tuna stock will take at least 15 years, and will be affected by any climate changes the ecosystems experience.
The Spatial Ecosystem and Population Dynamics Model (SEAPODYM) 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.
The study ‘Shifting from marine reserves to maritime zoning for conservation of Pacific bigeye tuna (Thunnus obesus)’ by John Sibert, Inna Senina, Patrick Lehodey, and John Hampton was published in the Proceedings of the National Academy of Sciences, October 30 2012.
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