Apropos to the final link in my post earlier today (technically yesterday, but who’s counting?), there is a wonderful article in this morning’s New York Times that demonstrates precisely the problem with managing fisheries in a sustainable manner:

In just the last 35 years, exploding markets for sushi-grade tuna, combined with intensifying industrial-scale hunts aided by satellites and spotters in airplanes, have devastated not only the fish but also many fisheries. [...]

The threat to the bluefin was underscored last week by researchers who have tracked hundreds of the fish on their ocean-spanning journeys using electronic tags. They found that the tuna that spawn in the west, which are most severely depleted, are further threatened by an ever-broadening gantlet of hooks, seines, harpoons, traps and now farm-style pens, in which netted fish are raised and fattened - all to supply the Japanese sushi trade. [...]

In all, 330 tags provided unparalleled records of fish as they repeatedly dove thousands of feet, traversed the ocean in a few weeks, and routinely crossed imaginary lines drawn nearly 25 years ago by tuna-fishing nations to divvy up what were thought to be separate eastern and western populations.

In many cases I’m an outspoken advocate of economic solutions to environmental problems, but the assumptions that simple fishery economics rely upon just don’t mesh with ecological reality. Specifically, fishery management relies on the assumption that we know what’s going on in the fishery. Even in small fisheries with local populations this is difficult to achieve, but bluefin tuna (Thunnus thynnus) have a range that is oceanic in scale. Bluefin have always been managed under the assumption that their massive range is split into two separate stocks on the East and West sides of the Atlantic (roughly divided by the 45th meridian). Dr. Block’s study (described above and in far greater detail in the Times article) indicates that the stocks mix, and that the two-stock management scheme we’ve been operating under for decades may actually be threatening the survival of the species.

Unfortunately, emerging methods of dealing with shrinking stocks such as creating marine reserves or aquaculture, aren’t practical for bluefin because of the extent of their range. The only viable option for protecting bluefin seem to be one form or another of catch limit, yet the sustainable catch level is determined by the same economic models that I’ve already criticized (and which presumably determined the existing catch limits, which are demonstrably unsustainable). The only solution then, is better data and fast. Ocean fish are notoriously difficult to study, especially when they have as broad of a range as the bluefin tuna. Studies like Dr. Block’s are a step toward preserving tuna both as a source of food and as an ecological resource.

Several tuna experts who were not involved with the new study said that Dr. Block's pointillist maps, showing the movements of some tuna for more than four years, were sufficiently concrete that they could force an end to the prolonged stalemate.

"Without her, we'd be in exactly the same place we were 15 years ago: a bunch of theoreticians waving their hands and a bunch of European fisheries politicians arguing the case based on no data," said Dr. E. Don Stevens, an emeritus professor of zoology at the University of Guelph in Ontario and an author of the 1994 National Academy of Sciences tuna study.

"If the managers do not accept this evidence," Dr. Stevens said, "then it seems to me that they will never accept any evidence and that their argument is not based on logic but rather is based on shortsighted political grounds.