Case Study: The Hilborn-Worm debate on the status of global fisheries

Matt Burgess-

In July 2009, a group of scientists, led by Boris Worm of Dalhousie University and Ray Hilborn of the University of Washington, published a study in the prestigious journal Science synthesizing the current state of knowledge on the status of global fisheries. The study found that a large fraction of well-studied fish populations have been severely depleted by fishing, but that many of these populations have begun to rebuild because of recent reductions in fishing pressure. The authors concluded that there is evidence of successful fisheries management in some regions, with parts of the United States and New Zealand as poster children, but that progress in monitoring and managing fisheries is still sorely needed in many other regions, especially in the developing world, where there are often few data, little management, and few alternatives to fishing. Recent studies (e.g. here and here) of even more comprehensive databases have supported these conclusions, and they now enjoy broad consensus in the scientific community.

But this consensus was hard won*.

Between 1998 and 2006, a series of high profile papers came out inferring alarming global trends in the status of fish populations from catch data. Boris Worm was an author on two of these papers. One, published in the journal Nature in 2003, concluded that the global abundance of large predatory fish (tunas, sharks, rays, codfishes, etc.) had declined by 90% since the 1950s, based largely on trends in catch-per-unit-effort (e.g. number fish caught/100 hooks). The second, published in Science in 2006, showed** an increasing trend (from 1950-2003) in the global fraction of fished populations that had ‘collapsed’ (defined by the authors as having declined by 90% or more in total annual catch), and remarked that extrapolating this trend into the future would result in the collapse of all fished populations by the year 2048.

These papers were criticized by many other scientists, among whom Ray Hilborn was particularly vocal, for misinterpreting the catch data they were using, and for not giving due credit to examples (including in the US) of successful fishery management. They argued that, while a fish population’s collapse could certainly lead to a decline in overall catch (as happened with northern cod, for example), there are other factors unrelated to population size that could also cause catch to decline. As an example, Hilborn pointed to Georges Bank haddock, whose catch had declined by over 90% in response to tightened regulations but whose population was thought to have increased, not collapsed. Catch-per-unit-effort (CPUE) data (used in the 2003 study) was a better measure of abundance than total catch, critics argued, but could still be misleading if spatial dynamics in fishing effort and non-linear relationships between CPUE and abundance were not taken into account.  Studies which had accounted for these factors found evidence for much smaller (than 90%) declines in most of the predatory fish species analyzed by Worm and his colleague (in 2003). Worm and others conceded that the catch data can have pitfalls, but pointed out that these were the only data available for most of the world’s fisheries, outside of a few developed countries, and argued that the overall global trends they were seeing were unmistakable***.

The debate reached its flash point in November 2006, when both Worm’s paper (containing the 2048 projection) and a paper by Hilborn criticizing the earlier series of papers (including Worm’s 2003 paper) came out, and made headlines around the world (Worm’s paper in particular). In interviews with the CBC and other media, Hilborn described Worm’s (2006) use of the catch data as “incredibly sloppy” and the 2048 projection as “just mind-bogglingly stupid”. Hilborn’s paper, entitled ‘Faith-based fisheries’, sharply criticized the journals for their handling of the peer reviews of the other papers and made the general suggestion that “many (fisheries) scientists have become advocates. An advocate knows the answer and looks for evidence to support it; a scientist asks nature how much support there is for competing hypotheses.” Daniel Pauly, a professor at the University of British Columbia, fired back in an article in The New Republic, which included a thinly-veiled suggestion that Hilborn and other critics of Worm’s (and others’) studies were “captured” by the fishing industry. Suddenly, a debate about facts and evidence had devolved into personal attacks in which the integrity and objectivity of the scientists themselves were being questioned. Attacks on a scientist’s integrity and objectivity can be career-killers if they stick, and are thus rarely taken lightly.

But just as the debate seemed to be widening into an unproductive chasm, or ‘war’ as some have put it, things took another unexpected, this time positive, turn. Hilborn and Worm found themselves debating each other on National Public Radio (NPR), and “found more common ground than we had expected”, as Worm later put it. Worm “actually seemed like a reasonable person,” Hilborn remembered thinking at the time. Realizing that a growing divide would not serve the science, the two decided to bury the hatchet. Over the two years that followed, they formed a working group with scientists from both sides of the debate to share data and perspectives, and try to reach consensus on the state of the world’s fisheries. The 2009 study was the product of this working group.

What made the Hilborn-Worm collaboration successful? In my opinion, three of the biggest keys seem to have been:

(i) A willingness to put their disagreements aside and start a constructive dialogue. This seems obvious, but needs to be said. Hilborn’s and Worm’s willingness to come to the table with an open mind is a powerful positive example for an academe in which big egos, ruthless competition, and obsession with being right are still far too common. I think Worm in particular deserves a lot of credit, as he arguably had some skin in the game as a junior faculty member being criticized by a much more senior, internationally-renowned researcher, in a manner widely perceived**** as questioning his integrity as a scientist. Having already stuck his neck out on the 2048 projection, it took courage and humility for Worm to stick his neck out again in the initial stages of the collaboration with Hilborn. Both Hilborn and Worm also deserve credit for agreeing to debate each other on NPR in the first place, at which point they may not have known how constructive it would end up being.

(ii) A mutual acknowledgment of a shared goal. As Worm put it, “We’re both motivated about improving the state of fisheries, so we wanted to find some consensus of where we are and where we’re heading.” Seeing a common goal likely contributed to the building of trust and respect among Worm, Hilborn, and their collaborators.

(iii) A clear and early distinction between differences in values and differences in interpretation of the data. As Hilborn put it, their values differed somewhat in that “I (Hilborn) was coming from a fisheries agency perspective, where the objective of fisheries was to produce food. You did that by depleting stocks well below the level they’d be in the absence of fishing; whereas, to a marine ecologist, any disturbance of the pristine system is in some sense negative.” But both realized that any such disagreement on the objective of fishing had no bearing on what the data say about the abundances of the fish populations, and how these abundances have changed. Once at this point, their differences seemed minor, if existent: both agreed that catch data had pitfalls, many fish populations were overexploited, but there were some examples of management success. Even if there was a remaining (values-related) difference in how these findings should be framed (‘there still cause for concern’ vs. ‘there are many signs of hope’), the 2009 consensus paper was able to highlight the agreement in what the data were saying, while acknowledging that both framing perspectives were valid and, importantly, not mutually exclusive.


*This Case Study draws on excellent previous summaries of the Hilborn-Worm debate and its resolution by Erik Stokstad, Cornelia Dean, Lizzie Buchen, and Trevor Branch, which I strongly recommend to any readers who would like more information.

**Although the 2048 projection dominated the news headlines surrounding Worm et al.‘s 2006 paper, it was only a brief side note in the paper itself, it its second-to-last paragraph. The paper’s main conclusion was that there was evidence of globally widespread declines in the abundance and diversity of marine species, and evidence that these declines could have significant negative impacts on the benefits people derive from marine ecosystems, including reductions in stability, productivity, recovery potential, and water quality. These conclusions have been influential, and far less controversial, within the scientific community.

***A more recent debate in Nature between Daniel Pauly, Ray Hilborn and Trevor Branch provides a good summary of the different points of view on whether catch data is appropriate for inferring fisheries status.

****Although news reports citing Hilborn’s ‘Faith-based fisheries’ paper, and his related criticisms of studies by Worm and other authors, have often painted a picture of a him accusing these authors of advocacy, it is important to note that Hilborn actually makes a point of stating (in the third paragraph of the paper) that his criticism is aimed at the peer review system and journals, not the authors: “As examples, let me choose papers by well-established professionals who have long records of significant work beyond the papers discussed below and I emphasize the problem is with the peer review and editorial system, not the authors of the papers.” Similarly, even Hilborn’s most aggressively worded criticisms were always (as far as I’m aware) clearly aimed at the studies or their parts, not the authors (e.g. the projection was “mind-bogglingly stupid”, the use of catch data was “incredibly sloppy” (not Worm or his colleagues personally)).


2 thoughts on “Case Study: The Hilborn-Worm debate on the status of global fisheries

  1. Pingback: A new debate in fisheries science; hoping to practice what I preach | The Tête-à-Tête

  2. Pingback: Academia’s conservative problem | The Tête-à-Tête

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