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Last year, only about 12% of the 1,533-ton quota was caught. The huge schools (between 80 and 200) of several-hundred-pound fish are gone. Suspected reasons range from overfishing in the eastern Atlantic and Mediterranean to environmental stress, but the fact is that we don’t know enough about the bluefin tuna to make any real guesses.
Formerly treated as two separate fisheries (east and west) with little to no mixing, recent tagging/tracking efforts have shown that there is up to 30% mixing between the populations. And a large disparity in fishing regulations and allowable sizes is further depleting the stock. (In the USA, 73″ / 250lbs is the minimum size, while European limits were just recently raised from 22lbs to 66lbs.) The recommended European quota of 15,000 tons for 2007 was ignored, in favor of a 29,500 ton quota (and an actual catch estimated at 50,000 tons.) Larger numbers of smaller fish mean they have no time to mature and reproduce, much less attain sizes legal in the USA.
Despite a call for a halt to fishing (from both the National Marine Fisheries Service and the US Senate) due to imminent collapse of the stock, the European managers (ICCAT) only reduced the quota slightly, eventally getting down to 25,000 tons in 2010.
There is also concern over environmental stresses, resulting in much leaner tuna over the past 15 years. Herring (a primary food source) has a healthy, near-pre-industrial biomass but individual fish are smaller at a given age than 10 years ago. (Smaller prey fish mean the tuna must work harder for a given amount of calories.) And arctic warming may be impacting algae growth, which affects the herring food supply.
A new systems-based management effort is beginning to be made. Instead of basing quotas off of that animal in isolation, the environment and ecology needs to be taken into account also. Many things affect a fish beyond it’s current and historical statistics, and the new methods will take this into account. But the question remains, will anyone listen?
(via CSM)
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