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Study Shows Upcoming WCPFC Tuna Ban Will Fail To Preserve Stocks

With the domestic fisheries of Indonesia and Philippines excluded from the ban – bigeye and yellowfin mortality will only rise.

Study concludes that the tuna fishing ban established by the Western and Central Pacific Fisheries Commission (WCPFC) will not achieve its objectives relating to a 30% reduction in bigeye tuna fishing mortality and may not maintain yellowfin fishing mortality at 2001- 2004 levels.

John Hampton and Shelton Harley, from the Oceanic Fisheries Programme of New Caledonia, prepared a document entitled Assessment of the Potential Implications of Application of CMM-2008-01 for Bigeye and Yellowfin Tuna for the next WCPFC Scientific Committee meeting, taking place in Vanuatu from August 10th-21st of 2009.

The CMM-2008-01, adopted by the WCPFC in December 2008, is the set of measures that seeks to reduce bigeye fishing mortality 30% from the 2001-2004 levels, and limit yellowfin tuna fishing mortality to its 2001-2004 levels, in order to maintain stocks at levels capable of producing the maximum sustainable yield (MSY).

This objective is pursued through a combination of measures involving longline catch limits, purse seine effort limits, a closure relating to purse seine fishing using fish aggregation devices (FADs) and a closure of two high-seas pockets (HSP) to purse seine fishing. Most of these measures have various exemptions or alternatives built in and are phased in over the period 2009-2011.

The study conducted a technical evaluation to check whether the CMM-2008-01 would reach its objectives and the answer was a loud “no”. For starters, they believe that using “2001-2004 or 2004” in the objective is not clear enough to know just how much does fishing mortality exactly have to be reduced to.

Concerning bigeye tuna, even the simultaneous implementation of all measures will, at best, maintain fishing mortality at the current high levels and cause declines in spawning biomass to levels below MSY levels:

“The measure fails in its objectives relating to bigeye tuna because the reductions in longline catch and the purse seine provisions fall well short of reducing fishing mortality in those components of the fishery to 30% less than 2001-2004 average levels. Even if those sectoral objectives were achieved, the overall objectives of the measure would not be achieved because the exclusion of the domestic fisheries of Indonesia and Philippines quarantines an important source of fishing mortality on juvenile bigeye tuna”, affirmed the study.

In addition, the study concluded that the closure of the HSP will result in a small reduction in bigeye mortality if the effort that would otherwise have fished in the HSP is transferred to other high seas areas, primarily to the east: “The net effect is an increase in bigeye fishing mortality compared to no closure of the HSP”.

Regarding yellowfin tuna, a ten years projection assumed that in 2018 fishing mortality could be 8% below to 15% above the 2001-2004, which demonstrates the confusion in using such ambiguous levels as objective. Different assessment models also place yellowfin recovery in a blurry situation: “Yellowfin tuna spawning biomass in 2018 is predicted to be similar to the 2001-2004 average or to decline slightly from that level, and to remain above or close to the MSY level, depending on the stock assessment model assumptions used”, concluded the study.

According to the WCPFC, the outcomes of the CMM-2008-01 will be the main issue discussed during the Scientific Committee meeting next month and it will provide scientific advice to the upcoming annual session of the Commission, next December in Tahiti.