Thursday, March 17, 2016


Recently, a team of researchers from the National Marine Fisheries Service, collaborating with the University of Massachusetts’ Large Pelagics Research Center, claimed to have discovered a new spawning ground for bluefin tuna.

On its face, the research seems fairly convincing.  Five- and six-day-old bluefin tuna larvae have been found in an area known as the “Slope Sea,” a piece of water that lies between the Gulf Stream and the edge of the continental shelf in the Mid-Atlantic Bight. 

Prior to the announcement, the only known North American spawning ground for Atlantic bluefin was located in the Gulf of Mexico.  The NMFS research team asserts that ocean currents could not have carried larval bluefin from the Gulf all the way to the Slope Sea in five days, meaning that such larvae must have been spawned somewhere else.

They also point to tagging data that shows smaller, 100- to 500-pound bluefin lingering in the Slope Sea region during certain times of the year.  A previous study, conducted by researchers at the UMass Center, suggested that western stock bluefin tuna mature significantly earlier than previously believed.  The two findings, taken together, could have a meaningful impact on the fishery for western stock bluefin.

Based on the two studies, it would not be unreasonable for people to argue that if western-stock bluefin actually mature while relatively young, and have more than one spawning ground, they can be sustain larger harvests than they could if they only matured after a decade or more and only spawned in one, vulnerable piece of the ocean.

However, a number of scientists specializing in bluefin tuna research remain properly skeptical of the team’s findings.  “Properly” skeptical, because the purpose of science is to discover the truth, not to make headlines or to tell people the things that they want to hear.  The NMFS team’s findings may well be correct, but it is the duty of the scientific community to try to poke holes in their paper and conduct further research to prove that they are wrong.

If, after the skeptics take their best shots at the data, the team's conclusions remain largely intact, then—and only then—it will be time to announce that bluefin do, indeed, spawn in the Slope Sea.

Many fishermen, however, are already celebrating, in anticipation of relaxed harvest regulations.  Sport Fishing Magazine, which targets recreational anglers, addressed the study by saying

“A bombshell in the world of fisheries management fell on March 7.  That’s when a report revealed new evidence that Atlantic bluefin tuna spawn off the northeastern United States…
“This finding transcends pure scientific discovery, as the study states, it possibly ‘leads to lower estimates of the vulnerability of this species to exploitation…’
“Put more simply, there are already suggestions being heard from various interests that bluefin that bluefin populations may be more resilient than we had thought, that stocks may be in better shape, and that more generous fishing quotas may be called for.”
Sport Fishing did express one cautionary note, pointing out that some members of the scientific community deemed the study to be preliminary, and feel that it would be premature to change the bluefin management paradigm.  However, it ended the announcement by saying

“…there is little doubt that this research will ultimately have implications for how we manage the ocean’s most valuable apex predator.  It will be interesting to see how this knowledge and more to come (as a search for more undocumented spawning grounds continues) will shape those implications.”
Over all, it was an exceptionally upbeat article, expressing none of the skepticism that should accompany news of new scientific discoveries.  In short, it was typical of how fishermen react when they hear news that might cause quotas to rise.

We saw the same sort of thing occur a few years ago in the Gulf of Maine cod fishery.

In 2008, NMFS produced a stock assessment that was the most optimistic in years.  Although it indicated that overfishing was still occurring, it also showed that the stock was making a strong recovery and was no longer overfished; estimated spawning stock biomass was 33,877 metric tons in 2007, seemingly well on its way toward reaching the SSB target of 58,248 mt.

When the results of the 2008 assessment were released, fishermen had no problems in accepting its conclusions, even though it seemed to be based on some somewhat suspect data—the supposed strength of the 2005 year class of cod, upon which most of the rosy analysis depended, was based on just one or two tows of the research vessel’s net, which captured very high numbers of fish.  No other tows were anywhere near as productive.

Still, despite this obvious warning sign, the fishermen didn’t question the data at all.  It said that the stock’s health was rapidly improving, which meant that they’d soon be able to harvest larger numbers of fish.

That was all that they wanted to know.

However, things turned around quickly just three short years later, after another stock assessment, released in 2011, said that the cod stock was in some real trouble.  The new assessment determined that the size of the spawning stock biomass was a mere 11,868 metric tons, roughly 1/3 of the 2008 estimate.  It employed a different mathematical model than the 2008 assessment, considered more sets of data, and was generally considered a more reliable estimate of the stock’s true size.

“The modeling approach used in this assessment represents a quantum leap, in terms of the ability to handle the underlying data and also its uncertainty.  There was far more rigorous treatment of the discard information and its consequence, and also the treatment of the landings and the survey data.”
But that’s a fishery scientist’s view.  Fishermen’s views were very different.

David Goethel, a commercial groundfisherman who sits on the New England Fishery Management Council,complained

“…why should it be accepted that the current data and model provide the best available science?
“…I think we need to have a thorough reexamination of everything here.  We need to examine cod, period.  We need new reference points, we need new [Stock Assessment Review Committee] boundaries.  We need all this done, and then we can address the underlying problems, if they still exist.  I’m not prepared to shut down the Gulf of Maine, or to put out a [limit on catch levels] that would shut down the Gulf of Maine until we address these issues.”
And that last sentence, of course, says it all.

Goethel had no problem with the 2008 cod stock assessment, because it had the potential to increase his catch.  But once the 2011 assessment came out, declared the 2008 assessment to be inaccurate and threatened to sharply decrease fishermen’s landings, it was time to condemn the science, call for additional research, reset all of the existing parameters and start over again.

For while many fishermen are willing to accept science that leads to increased harvest as unquestionably right, they are even more inclined to declare any science that leads to decreased landings as completely and irreparably wrong.

It's a problem that managers have had to live with for years, and it's not likely to go away at any time soon.  But it makes it very clear why, when setting annual catch limits, scientists, and not fishermen, must have the last word.

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