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Mark:

As far as I can tell, you missed the point--that we're seeing a  
decided shift in societal objectives from maximizing yield to  
maintaining intact ecosystems and that this shift largely explains  
the crisis. Whether or not you agree with this explanation, your  
piece contributes to the general hysteria and misrepresents an  
unusually well-informed and cogent presentation that folks should  
judge on its own merits. By all means, critique Hilborn's arguments-- 
I don't agree with everything he said either--but please be honest  
with those you're trying to convert.

Cheers, Pete

Peter A. Nelson
University of California, Davis


On Nov 22, 2006, at 8:48 AM, Mark Powell wrote:

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>
> The Good Depletion
>
> Fish depletion is not a problem, it's the goal of fishery  
> management. So
> says Ray Hilborn in "Re-interpreting the Fisheries crisis." So don't
> worry about disappearing fish, it's part of the grand management plan.
>
> Thus we have The Good Depletion; it allows us to maximize our fish
> catches. Or so say the equations. The Good Depletion has us  
> liquidating
> the big fish, shrinking population size by 60-80%, and thus increasing
> the "productivity" of exploited fish populations. Mr. Hilborn says the
> decline shown in the figure is not a problem, because we're still
> catching plenty of fish.
>
> The Good Depletion was an advance in the mid 1900's, and it has some
> practical value. But it's time to give it a gold watch, a rocking  
> chair,
> and a graceful retirement. Unfortunately, Mr. Hilborn and others  
> want to
> keep it working in it's dotage.
>
> We need a new paradigm for 21st century fisheries, and here's what I
> think it needs. It should maximize the probability of good  
> reproduction
> years by valuing big fish (because of high reproductive value) and  
> life
> history diversity (e.g. wide range of spawning times and places). It
> should maintain fish populations' geographic and age distribution. In
> brief, it should emphasize the value of what's in the ocean, not what
> comes out. Fishing should "make hay when the sun shines" by fishing  
> hard
> during fish population booms, and switching to other species during  
> lean
> times when reproduction is weak. To me this would be good
> ecosystem-based fishery management.
>
> This whole fight reminds me of the transition in managing public
> old-growth forests of the Pacific northwest. When I came of age, we  
> were
> clearcutting old-growth forests to produce maximum sustained yield,
> following the rationale of The Good Depletion (forestry version). It
> failed for many reasons, such as the forests that didn't regrow  
> well in
> hot southern Oregon, or the wildlife that went missing in massive tree
> farms.
>
> Science has undermined the assumptions of The Good Depletion  
> (fisheries
> version). Equilibrium doesn't exist, all spawners are not equal, life
> history diversity is important, the ecosystem context matters, etc.,
> etc.
>
> Interestingly, Mr. Hilborn says this within the family, just not in
> public when The Good Depletion is threatened by outsiders.  
> According to
> Mr. Hilborn and colleagues: "For some years the concept of maximum
> sustained yield (MSY) guided efforts at fisheries management. There is
> now widespread agreement that this concept was unfortunate," and
> "Distrust claims of sustainability. Because past resource exploitation
> has seldom been sustainable, any new plan that involves claims of
> sustainability should be suspect."
>
> Circling the wagons around The Good Depletion won't save it. I suppose
> the testiness of its defenders (watch the video link) is evidence  
> of the
> coming paradigm shift. Fishery scientists would do well to help
> fisheries make the transition, rather than propping up The Good
> Depletion until it's really too late and everything falls with a great
> crash.
>
> Mark Powell
> live links to sources at
> http://blogfishx.blogspot.com/2006/11/good-depletion_22.html
>
>
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