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Subject: Re: Is overfishing a scientific or legal term?
From: "Trevor J. Kenchington" <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Fri, 27 May 2005 23:30:49 -0300

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I go away on a 3-day business trip and come home to an e-mail inbox with 
multiple copies of an article from the New Bedford "Standard Times" in 
which I was quoted, plus a spin-off Fish-Sci thread with upwards of a 
dozen messages! I had no idea that so many people cared about a few 
words of mine.

Mike Flaherty started the thread with:

> An article titled, "Scallops overfished for past 2 years, official says",
> appeared on the front page of today's New Bedford Standard Times.
> There was one excerpt in it which gave me pause...
> ===============================
> "Overfishing is a legal term, not a scientific term, and is therefore not an
> accurate way to evaluate the health of the scallop fishery, Dr. Kenchington
> said."
> ===============================
> As I roughly understand things, "overfishing" is defined as a point beyond
> which harvest/mortality levels exceed sustainable levels in a fishery.  It
> is further my understanding that the thresholds for sustainability are
> arrived at scientifically.  If this is true, then isn't overfishing truly a
> scientific term?  More importantly, is it a reasonably accurate way to
> evaluate the health of a fishery?

Most members of Fish-Sci will have seen nothing more of the article (a 
brief report on one specific meeting, of only limited interest outside 
New England), so the context of my comment is missing. Indeed, the 
reporter who prepared the article drew that and a couple of other quotes 
out of our lengthy conversation (more of a monologue on my part, I'm 
afraid), which dipped into some technical issues that very few people 
understand, even those who have had far more explanation than I gave 
her. If she didn't quite catch the import of all my remarks (as she did 
not in this case), it was no fault of hers.

But since Mike has chosen to make an issue of it, I can provide a better 
explanation for the very different Fish-Sci audience:

I think we all understand what "fishing" is and "overfishing" clearly 
means too much fishing. That is almost "common English" (as Justin 
Johnston noted). The problem comes with what we mean by "too much".

On the biological side, there are the usual run of types of 
"overfishing": Growth, Recruitment and so forth, as Will Le Quesne 
pointed out, though as we move into ecosystem-based management, we will 
likely have to coin yet other versions ("Ecological Overfishing" 
anyone?). Then there is the bio-economic "Economic Overfishing", which 
should perhaps be complemented with "Socio-economic Overfishing", if the 
optimum level of fishing which is being exceeded was defined on the 
basis of broader considerations than bio-economics alone.

Still technical but not scientific is "Regulatory Overfishing", which 
seems to mean running over a set catch limit.

However, in the United States, "overfishing" is specifically defined in 
the Magnuson-Stevens Act and thus has a legal meaning -- similar to but 
not quite synonymous with some of the technical meanings. The definition 
in the Act is considerably expanded and interpretted within the 
Guidelines to National Standard One. To oversimplify, they define 
"overfishing" as a fishing mortality rate greater than F[MSY] (itself a 
very wooly concept). Those Guidelines are required by the Act and were 
formally published in the "Federal Register" but they do not have the 
status of regulations. Whether or not their version of "overfishing" is 
a legal term is a matter of semantics on which I am more than happy to 
defer to the judges of the U.S. federal courts.

Also under the Magnuson-Stevens Act, each federally-managed fishery has 
its own Fishery Management Plan which is required to provide a specific 
definition for F[MSY] for the resources that fall under that FMP. In the 
case of the Atlantic Sea Scallop FMP, covering all Placopecten 
magellanicus in U.S. waters, F[MSY] is defined to be equal to F[MAX] for 
legal/regulatory purposes, while F[MAX] is currently estimated to be 
0.24. A fishing mortality rate exceeding that number is "overfishing" in 
the legal sense in the United States. Such "Legal Overfishing" (to coin 
a phrase) is not allowed under the Act, while various procedures come 
into play if F should exceed the set limit.

Scallops, however, are largely sedentary by the time they reach 
commercial size. As various authors from Beverton & Holt onwards 
(particularly John Caddy) have noted, the yield-per-recruit logic which 
leads to estimates of F[MAX] doesn't make much sense with sedentary 
resources. To really harvest the theoretical maximum yield-per-recruit, 
we would need to apply fishing effort such that each individual scallop 
had an annual probability of harvest equal to F[MAX]. At least, we 
should set F equal to F[MAX] in each very small local area. Applying a 
mortality rate of F[MAX] averaged across the whole resource just won't 
do it. It most certainly won't when most scallops are locked up in 
closed areas while most fishing effort (i.e. most fishing mortality) 
happens in areas where the resource has been thinned by prior fishing -- 
which is pretty much the current situation in the U.S. scallop fishery.

Yet management of that fishery faces a whole bunch of extra 
complications. For one thing, the scallop fleet is highly mobile, with 
some individual boats fishing everywhere from Georges Bank to Virginia 
-- while other captains only want to work certain grounds. The primary 
control on F, restrictions on the number of Days-at-Sea per boat per 
year, is not area-specific and cannot readily be made area-specific 
without serious disruptions of the existing socio-economic structures of 
the scalloping communities. Even if ways could be found around that, the 
available data sets are at least an order of magnitude too limited to 
allow management based on spatial units corresponding to the spatial 
scales within which adult scallops live. (Their eggs and larvae are, of 
course, much more mobile.) Further, if the FMP did separately define a 
dozen or so units, each with its own legal "F[MSY]", the manageemnt 
system would be overwhelmed by the need to separately assess each unit 
and to report the results of each such assessment to the U.S. Congress 
(as the Magnuson-Stevens Act requires for each management unit 
recognized in an FMP). Add to that lot, a temporal complexity: We 
actually want higher F in local areas when the vagaries of recruitment 
have supplied a preponderance of older scallops but lower F where there 
is an incoming year-class which is still growing quickly. (Such rotation 
has the potential to squeeze a few percent more yield from the 
resource.) Anybody who relishes trying to explain to the public, 
politicans and the courts why, in any given year, some scallop "stocks" 
are seeing "overfishing" and others underfishing, and why that is OK, is 
more than welcome to the task. What we can't have is a court-ordered, 
rigid system in which F in each local area is forced below F[MSY] every 
year, on pain of immediate closure of the entire fishery.

A few years back, we tried to come up with an operational definition of 
sea scallop "F[MSY]" that would capture all those complexities, while 
escaping the serious pitfalls, but the best ideas available within the 
time constraints really didn't meet the challenge. So (at my urging as 
much as anything), the New England Fishery Management Council opted to 
make the legal definition of "F[MSY]", in the scallop FMP, a single 
fishery-wide value of F=0.24. That defines sea scallop "overfishing" for 
legal purposes, while we get on with the job of actually managing the 
fishery so as to harvest optimum yields from the resource, amidst all of 
the spatio-temporal complexity (and also while we face up to the 
challenge of devising a better definition).

Now: The latest update assessment for this fishery, which was first 
announced a couple of weeks ago but again at a meeting on Wednesday of 
this week, produced a value of F[2004]=0.34. By the legal or regulatory 
definition of sea-scallop "overfishing", and using that term in its 
very-definitely legal sense (as it is defined by the Magnuson-Stevens 
Act), 0.34 exceeds 0.24 and thus there was "overfishing" in the scallop 
fishery last year.

Biologically, nothing is so simple. There are important scallop grounds 
on Georges Bank where no scallop harvest has occured in a decade 
(because of closures to protect groundfish, which have now morphed into 
closures to protect groundfish habitat). Those areas are grossly 
underfished for scallops, by any biological definition. However, there 
are areas off New Jersey which were fished very hard last year -- 
certainly at levels which, if sustained, would represent biological 
overfishing (though part of those areas is now in a rotational closure 
and another part is recently out of such a closure, so the "sustained" 
aspect is complex too).

In bio-socio-economics, matters get even more murky (if that is 
possible). The emphasis on F[MSY] is a legal issue, while the Act also 
implicitly supposes that F[MEY]<F[MSY] (though the U.S. Congress never 
got into the technical terminology which might have stated that 
inequality directly). For most finfish fisheries, I think those are 
sensible starting points for an operational definition of "overfishing". 
Scallops, however, (perhaps because they are herbivores that crop 
phytoplankton directly) are incredibly robust to fishing pressure. You 
can beat them down with heavy fishing, back off a bit, and they will 
come bouncing back. So we are not faced with the sort of population 
collapses that bedevil management of fisheries for top predators. 
Meanwhile, the existing market for scallops wants a small animal (though 
that is changing fast as new markets are being developed for the large 
"meats" now being produced), which can only be obtained in quantity 
through Growth Overfishing, as it is normally understood in the 
biological sense. Furthermore, the social objectives of the scalloping 
communities would be advanced by having many people working at moderate 
catch rates, rather than the current few taking huge catches from very 
high biomasses at relatively low F. Hence, if there was no legal 
standard requiring something very different, I suspect that the 
socio-economic optimum in this one fishery (long-term, not just 
short-term) would set F appreciably higher than F[MSY]. (That isn't 
legal in the United States and nobody is suggesting that it should be 
done. I am just suggesting what "overfishing" might mean in this 
specific fishery if the word were free of all legal overtones.)

So, "overfishing" is not purely a legal term, as Becky Evans had me 
implying in her article in the "Standard Times" but, in the United 
States, it has a legal meaning in addition to its technical and common 
meanings. However, the "overfishing" that was announced and emphasized 
at the meeting which she reported on was "overfishing" in the legal 
sense and was defined as such relative to a rather arbitrary, legal 
standard set in the Sea Scallop FMP. Certain parts of the resource 
likely are undergoing "overfishing" in biological and other senses. 
Certain parts are certainly seeing no scallop harvesting at all. Whether 
that all adds up to "overfishing" relative to anything but the legal 
standard is a moot point. Hence my explanation to Becky, briefly noted 
in her article, that the "overfishing" announced that day was a legal 

It has to be ended, of course. Because it is "Legal Overfishing", the 
law must and will be obeyed. Interestingly, initial estimates suggest 
that it already has been, and without any reduction in boat-days or 
hours of dredging: Closure of one rotational area has moved the fishing 
effort into areas where scallops are less dense, producing lower F per 
boat-day. Which just goes to show the strange and tenuous link in this 
fishery between "overfishing" in real-world senses (biological, economic 
or whatever) and in the legal sense -- which was the kind of 
"overfishing" that stirred things up on Wednesday.

Trevor Kenchington
Consultant scientist to the Fisheries Survival Fund, an organization of 
scallop vessel owners

Trevor J. Kenchington PhD                         [log in to unmask]
Gadus Associates,                                 Office(902) 889-9250
R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555

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