Sunday, November 19, 2006

The (fishery management) empire strikes back

Fishery scientist Ray Hilborn is mad, and he isn't going to take it anymore. He's launched a new attack on critics of fishery management. His lecture illuminates the strengths and weaknesses of his profession.

Mr. Hilborn has a clear bottom-line message: it's the catching of fish that matters. If fish are still coming over the side, then all is well. It's a message straight out of his
classic fishery science textbook. Fish depletion? It's not a problem, it's part of the plan.

In celebrating YIELD (# of fish caught) as the King, the empire crumbles. Apparently, fishery scientists have yet to learn that they neglect the fishes' ecosystem at their peril (and at the peril of the fishermen). With near-religious faith, they assume that fish depleted today will boom again tomorrow. It's a comforting kind of faith, that unfortunately hasn't proven true.
Too many fish don't recover after being fished into depletion.

Mr. Hilborn's profession seems set to play out a tragic verison of the oath of Hemingway's Santiago: "Fish, I love you and respect you very much. But I will kill you dead before this day ends." This is poor service to the fishermen Mr. Hilborn so clearly respects.


Ian said...

I'm often impressed by your blog, but this latest post reflects a tendency to oversimplify your subject for the sake of making a point. Maybe that's what blogs are for, but I think you could rise above that. The bottom line I got from Ray Hilborn's lecture was not, "it's the catching of fish that matters." The message I got was that, as a society, we need to define our objectives, and in doing so, we will often face trade-offs between the objectives of employment, profitability, yield, protection of ecosystems. Hilborn notes that our preferences are shifting, and that, "the conservation NGOs have been very effective at changing the objectives of society...we're much more concerned about maintaining ecosystem integrity...that's an encouraging thought."

I don't agree with everything he says, but demonizing Dr. Hilborn and suggesting that all fishery scientists are blockheads doesn't seem like a fruitful strategy for improving the current state of affairs, especially given that you often support your arguments by citing the work of fisheries scientists with whom you agree.

Mark Powell said...


Thanks for the comment. Glad you like blogfish.

Mr. Hilborn's lecture was close to an hour, and he said a lot. I didn't comment on all of it, just a glaring aspect that clarifies the divide between "classic" fisheries science and critics of that approach. To me that's the main point of his lecture, even if you (or Mr. Hilborn) think otherwise.

I agree that he emphasized the conflict of goals, and that's an interesting aspect of his lecture that may deserve discussion. I think he's right on that point. There are other interesting parts of his lecture that might deserve more comment. If others are interested in what I think, I'll respond more fully later.

Now to the glaring problem of focusing on YIELD (fish catch) only...

Mr. Hilborn doesn't even seem to notice that he talks almost entirely about fish catches (YIELD) when he discusses the health of fisheries. It's such a fundamental part of fishery science that it's taken for granted. It's a MISTAKE, and we should know better by now, too many fisheries had high yields until just before a crash. To me that's the most salient point of his lecture, it appears that he hasn't yet figured out it's a mistake. That is worthy of criticism, IMO, I'm curious if you disagree and why. If you read this, please answer. Is it ok to focus almost entirely on YIELD in discussing fish population health?

There's more to criticize. His focus on yield is linked to his view that depletion is ok, in fact it's the goal of fisheries. This assumes that all spawners are equal, we don't need big old fish, that ecological relationships won't shift, and that any depleted species will recover just fine. The only change he seems to think is appropriate is considering lower yield targets. He seems to aver at the end of his lecture that he thinks biomass targets should be higher than Bmsy (higher than 20-40% of unfished levels), but he doesn't emphasize that. To me, this neglects much that has been learned in the last decade or more.

Finally, I don't think I demonized Mr. Hilborn. He certainly poked his critics harder than I poked him. I said he illuminated the strengths and weaknesses of his profession, and then proceeded to talk about one glaring weakness that doesn't necessarily apply to all fishery scientists equally. I still contend that a near-exclusive focus on yield is a problem, and I criticize fishery science and scientists to the extent that they focus on yield and neglect other measures of fish population health. Mr. Hilborn's lecture is, IMO, very guilty of this mistake. I didn't mean to cast all fishery scientists as identical and equally worthy of this criticsm. However, I have noted that plenty of other fishery scientists have said "hooray" to this lecture as an overdue debunking of the "litany" of criticism.

To Mr. Hilborn and anyone cheering this lecture. Circling the wagons is not the answer. Learn, grow, and encompass the criticism, especially where it challenges the YIELD-centric paradigm.


Ian said...

Thanks for a more complete critique.

Is it ok to focus almost entirely on YIELD in discussing fish population health?

No, I certainly don't believe that. Maintenance of yield (especially in the short term) doesn't indicate a healthy population. However, neither does a reduction in yield (especially in the presence of new management measures) necessarily indicate an unhealthy population, and yet this second assumption was the basis for the Worm et al. prediction of all currently fished taxa collapsing in 2048. Given that landings are the most readily available data for so many fish stocks, it seems to me that efforts to draw broad conclusions about the state of the worlds fish populations tend to draw on this information and sweep a lot under the rug in the process.

Mark Powell said...


Touche', excellent point! Worm et al focused on yield too, and neither they nor Hilborn can use yield as an indicator with complete confidence. Agreed, it's problematic to diagnose fishery health or crisis based solely on catch history. FWIW, I actually doubt that fishery restrictions are responsible for the Worm et al graph on declining fisheries, since no managers could sustain the political cost of a 90% reduction in catch unless fish were seriously depleted. But I agree that your point is valid...yield is used as an indicator on all sides of conservation debates.

Your points, and some backchannel comments have prompted me to look at another aspect of management for tomorrow, hope you find it intersting.


Aaron said...

Have you taken a look at any of the papers that have been critical of Boris Worm and Ransom Myers recent string of papers?
Maunder et al. 2006 ICES 63(8) pg. 1373-1385
Polacheck, T. 2006. Marine Policy 30(5) pg. 470-482
Walters, C 2003. CJFAS 60(12) 1433-1436

These papers seem to indicate that there are some fairly major flaws in their studies that have been receiving lots of media attention. Additionally, the Marine Policy paper points out some apparent problems with the way Nature has been dealing with the publication of fisheries papers and the critiscism of the "rapid decline of large predators" paper.

Finally, just a quick comment on the previous comments. I suspect that Hilborn is probably quite aware that it is more than just an issue of yield (i.e. catchability and range expansions/contractions) also play a role.

Mark Powell said...


I'm not taking sides in Hilborn vs. Myers or Worm. I'm exploring the fascinating and important controversy over "The Good Depletion" (see Wed Nov. 22 post). Ray Hilborn says many things, but what interests me the most is his defense of depletion. He says depletion is not a failure, it's the goal of maximum sustainable yield management.
And, he says don't blame scientists, society chose the goal.

Two very debatable points. As I said in "The Good Depletion," society didn't really get to choose, society was misled into choosing The Good Depletion (MSY) as a goal. And, it's not a good idea to deplete stocks by 60-80% and assume a fish population will do what the MSY equations predict (thrive and increase productivity).

It's an important question worthy of debate: Is depletion a good goal for fishery management?


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