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Trouble Brewing Elsewhere

December 24, 2010
tags: ,

There is another angle to the problems with the WCPFC.

Bigeye tuna is found in all tropical and sub-tropical waters of the world.  Here’s the map of their occurrence:

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And the driver of overfishing in the WCPFC is rapidly growing everywhere.  This is the use of “fish aggregating devices” (FADs).   Skipjack tuna, juvenile bigeye tuna, and yellowfin tuna are attracted to floating objects.  So purse seine fishing vessels “set” on intentionally laid FADs.

FAD fishing is very effective, but is resulting in the accidental catch of juvenile bigeye and yellowfin.  This drives up the catch of these species, and leads very quickly to overfishing.

Already the Indian Ocean Tuna Commission (IOTC) has said it is concerned about the growing use of FADs and increasing pressures on its tuna stocks.

In the Atlantic, the International Commission for the Conservation of Atlantic Tuna (ICCAT) has found that it is not clear if overfishing is occuring or if the entire stock size is below that level yielding the maximum sustainable yield.   The 2010 stock assessment notes:

“The biomass at the beginning of 2010 was estimated to be at between 0.72 and 1.34 (80% confidence limits) of the biomass at MSY, with a median value of 1.01 and the 2009 fishing mortality rate was estimated to be between 0.65-1.55 (80% confidence limits) with a median of 0.95.”

In the worst case, then, there could be massive overfishing.

Finally, the Inter-American Tropical Tuna Commission (IATTC) found that the Eastern Pacific bigeye stock was both experiencing overfishing and was overfished in 2008.   This changed in 2010 after the commission tinkered with their models.  Thus this leaves massive uncertainty.

It does seem that FADs are perhaps too effective to be allowed.  Though some would like to see a more careful scientific development of appropriate FAD usage.  My feeling is that the ocean is too big and too poorly monitored to ever expect FADs to be used in a sustainable way.

Here’s an excellent Greenpeace video on FADs:

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And here’s a good video showing purse seine fishing in the Pacific, as carried out by a Solomon Island purse seine vessel.

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