Thursday, June 27, 2019

FISHERIES MANAGEMENT: SCIENCE VERSUS STORIES


Fishery management takes place in a larger world.  Thus, it’s hardly surprising that ideas and opinions that arise outside the fisheries context are relevant to management issues.


“Too many leaders and influencers, including politicians, journalists, intellectuals, and academics, surrender to the cognitive bias of assessing the world through anecdotes and images rather than data and facts.”
Anyone who has ever attended a fisheries meeting understands why that sentence rang a bell, because there is probably no other venue where so many people try to pass off so many anecdotes—mere stories—as facts.

Such anecdotes take many forms.  Some are stories told by people who oppose further restrictions on harvest, and are trying to grasp onto any tale that might stave off additional regulations.  Some are observations told by fishermen who don’t understand fisheries science, and are merely reporting what they think that they see.  And others reflect honest and accurate observations of local abundance and local catchability, which might not reflect the overall condition of the stock.

Gulf of Maine cod provide an example of one such situation.
A few years ago, it became apparent to most that the cod were in serious trouble.  A new, peer-reviewed stock assessment revealed the stock was badly overfished, and that abundance had fallen to well below 10% of the target level.  Yet, as reported in the blog TalkingFish.org, fishermen argued that

“Cod are everywhere.”
The Commonwealth of Massachusetts agreed to conduct its own statistically-valid survey, to see whether it could develop data that would support the fishermen’s claims.  Just the opposite happened.  The survey results effectively confirmed the findings in the stock assessment:  the cod stock was in bad shape.

Yet the fishermen rejected the survey’s data.  According to TalkingFish, one outspoken industry representative told the Boston Globe that

“The state survey literally does zero to improve our confidence.  You can’t just sample anywhere.  You have to go where the cod are supposed to be.”
Such statement says a lot about too many fishermen’s chronic misunderstanding of survey and assessment techniques.  As fishermen, their job is catching fish, and if they are in the business for any length of time, they get pretty good at it.  They learn where fish will be under various conditions, and know how to chase down and find even small concentrations of fish, located in very specific areas, in order to bring home a good catch.

They ignore all of the places where they don’t expect fish to be, because it’s pointless to fish there.

Thus, when they drop down their hooks, deploy their gill nets or tow their trawls, they usually end up catching a fair amount of fish.  They tend to discount the fact that the places that the fish still inhabit are surrounded by vast expanses of once-productive, and now largely empty, bottom.

They know other fishermen who are catching fish, too.  All of their success stories, considered together, provide a very selective, and very distorted, overall view of fish abundance, composed of individual anecdotes, and not of data.  But to a fishermen who wants to believe that all is well with the stock, they serve as “proof” that the science is wrong.

Although that example is drawn from the commercial fishery, we frequently see similar examples emerge from the recreational fleet.  They are very common when dealing with migratory species such as striped bass and bluefish, which can be very abundant at certain times and places as they move along the coast.

This spring, for example, many fishermen who targeted the big, pre-spawn female striped bass that were staging in Raritan Bay and lower New York Harbor before moving into the Hudson River to breed rejected a recent stock assessment’s conclusion that the striped bass was both overfished and subject to overfishing. 

After all, how could they be filling coolers with bass (often legally, sometimes not) if there weren’t many bass to be found?  Suggestions that striped bass need further protection are often met with scorn and outright hostility, as anglers focused on local, transient abundance fail to see the bigger picture that was captured by the stock assessment.  Few ever stopped to question whether, in a time of relative scarcity, it made any sense to kill large, fecund females on their way to the spawning grounds.

Once again, too many fishermen took reports out of context, and allowed tales of abundance in one particular place, at one particular time, to trump a detailed, data-driven and peer-reviewed assessment of the health of the striped bass stock.

Similarly, stories of striped bass abundance in federal waters more than three miles from shore, where fishing for bass is illegal, are being used by some folks who are trying to impeach the findings of the latest stock assessment.

The stories all take about the same format.  Someone will get up at a meeting and declare something like “My pals Frankie and Joey were out in the canyon fishing for tuna, and on their way back to the market they ran across acres—acres, they said—of striped bass maybe 20 miles from shore.  They told me that there were so many bass that when they ran through the school, their depthfinder lit up and showed the bottom 20 feet under the boat, when they were still in 150 feet of water.”

That story gets repeated by a few people a few times in a few different forms, and maybe Frankie and Joey themselves are at the meeting to tell it themselves, and everybody looks at one another with satisfied expressions on their faces, nodding and fully convinced that they just “proved” that the science is wrong and that there are plenty of striped bass offshore—something all real fishermen know is the truth—but that the scientists who count fish, again, just don’t know where to find them.

Such stories can even convince legislators who are weak on the details of fisheries science. 


“used flawed data that measures the Atlantic Striped Bass stock based on the entire eastern seaboard, yet failed to account for the Atlantic Striped Bass outside of the 3-mile fishing area, assuming that fish abide by arbitrary bureaucratic boundaries.  Alternative data that shows the Striped Bass stock is in a better place outside of the 3-mile was…thrown out by the [Atlantic States Marine Fisheries] Commission… [emphasis added]”
Thus, we see exactly the problem that the piece in The Harvard Gazette alluded to, which arises when a politician falls victim to anecdotes, and confuses such anecdotes for data and for facts.  For the stories told about striped bass being encountered offshore does not rise to the level of data—not even to the level of “alternative data” which, like “alternative facts,” tend to distort what is true.

That doesn’t mean that the fishermen’s observations can’t lead to real, statistically-valid data.  But to do that, a scientifically rigorous investigation must take place.  Saying “Frankie and Joey know what they saw,” just isn’t good enough.

If someone wanted to prove that there are striped bass offshore that were never included in any of the surveys considered in the stock assessment, they wouldn’t do that merely by providing an accounting of times that such fish were seen more than three miles from shore—even if such list was fairly detailed, and contained dates, defensible estimates of the number of fish seen each time, etc.  In the end, all that such list would contain are stories.  A lot of stories, to be sure, but still nothing more than anecdotal reports.

To truly prove the assertion that there are uncounted bass offshore, supporters of such claims would first have to create a “null hypothesis” that, in this case, would assume that there are no such striped bass in federal waters, and then collect valid data to prove that the null hypothesis is wrong.

They might, for example, get an exempted fishery permit that allows them to catch and tag bass in federal waters, then see how many of those tagged fish show up in the inshore surveys used to prepare the striped bass stock assessment.  If it turns out that none of the tagged fish show up in inshore surveys after a reasonable period of time has passed, then there would be at least some data that tends to contradict the null hypothesis, and so supports their claim.


That real data, which shows the vast majority of “offshore” fish tagged soon returned inshore, is not completely dispositive of the question, but it tends to strongly support the null hypothesis, and thus does not support any “alternative data”—that is, fishermen’s stories—suggesting that there are uncounted bass swimming somewhere in federal waters.

And that’s how fisheries management—and any science-based issue—is supposed to work:  Driven by facts, not by anecdotes and compelling images.  As The Harvard Gazette’s piece concluded

“We need to make ‘factfulness’ an inherent part of the culture of education, journalism, commentary, and politics.  An awareness of the infirmity of unaided human intuition should be part of the conventional wisdom of every educated person.  Guiding policy or activism by conspicuous events, without reference to data, should come to be seen as risible as guiding them by omens, dreams, or whether Jupiter is rising in Sagittarius.”
Because fish stories can be entertaining, but they are not data.  

And they shouldn’t drive fisheries policy.

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