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SEAFOODNEWS.COM by John Sackton – January 25, 2016 — Last week the media was full of a new round of global fishery disaster stories, prompted by an article in Nature Communications by Daniel Pauly & Dirk Zeller affiliated with the Sea Around Us project.
Pauly and Zeller state that FAO global fisheries data has underestimated prior catch, and that therefore if this is taken into account, the decline in fish catch from the peak in the late 1990’s is not 400,000 tons per year, but 1.2 million tons per year.
“Our results indicate that the decline is very strong and is not due to countries fishing less. It is due to countries having fished too much and having exhausted one fishery after another,” said Pauly to the Guardian newspaper. As a result, a new round of handwringing ensued about global overfishing.
But, the facts don’t support Pauly’s interpretation. Catch rates are simply not a suitable measure of fisheries abundance. In fact, declines in catch rates often are due to improvement in fisheries management, not declines in abundance.
Over at cfood, a number of scientists specifically rebutted the premise of Pauly’s article.
Ray Hilborn of the University of Washington says:
This paper tells us nothing fundamentally new about world catch, and absolutely nothing new about the status of fish stocks.
It has long been recognized that by-catch, illegal catch and artisanal catch were underrepresented in the FAO catch database, and that by-catch has declined dramatically.
What the authors claim, and the numerous media have taken up, is the cry that their results show that world fish stocks are in worse shape than we thought. This is absolutely wrong. We know that fish stocks are stable in some places, increasing in others and declining in yet others.
Most of the major fish stocks of the world, constituting 40% of the total catch are scientifically assessed using a mixture of data sources including data on the trends in abundance of the fish stocks, size and age data of the fish caught and other information as available. This paper really adds nothing to our understanding of these major fish stocks.
Another group of stocks, constituting about 20% of global catch, are assessed using expert knowledge by the FAO. These experts use their personal knowledge of these fish stocks to provide an assessment of their status. Estimating the historical unreported catch for these stocks adds nothing to our understanding of these stocks.
For many of the most important stocks that are not assessed by scientific organizations or by expert opinion, we often know a lot about their status. For example; abundance of fish throughout almost all of South and Southeast Asia has declined significantly. This is based on the catch per unit of fishing effort and the size of the individuals being caught. Estimating the amount of other unreported catches does not change our perspective on the status of these stocks.
In the remaining fisheries where we know little about their status, does the fact that catches have declined at a faster rate than reported in the FAO catch data tell us that global fisheries are in worse shape than we thought? The answer is not really. We would have to believe that the catch is a good index of the abundance.
Figure 1 of the Pauly and Zeller paper shows that a number of major fishing regions have not seen declines in catch in the last 10 years. These areas include the Mediterranean and Black Sea, the Eastern Central Atlantic, the Eastern Indian Ocean, the Northwest Pacific and the Western Indian Ocean. Does this mean that the stocks in these areas are in good shape, while areas that have seen significant declines in catch like the Northeast Atlantic, and the Northeast Pacific are in worse shape?
We know from scientific assessments that stocks in the Mediterranean and Eastern Central Atlantic are often heavily overfished – yet catches have not declined.
We know that stocks in the Northeast Pacific are abundant, stable and not overfished, and in the Northeast Atlantic are increasing in abundance. Yet their catch has declined.
Total catch, and declines in catch, are not a good index of the trends in fish stock abundance.
Michael Kaiser of Bangor University commented:
Catch and stock status are two distinct measurement tools for evaluating a fishery, and suggesting inconsistent catch data is a definitive gauge of fishery health is an unreasonable indictment of the stock assessment process. Pauly and Zeller surmise that declining catches since 1996 could be a sign of fishery collapse. While they do acknowledge management changes as another possible factor, the context is misleading and important management efforts are not represented. The moratorium on cod landings is a good example – zero cod landings in the Northwest Atlantic does not mean there are zero cod in the water. Such distinctions are not apparent in the analysis.
Also David Agnew, director of standards for the Marine Stewardship Council, said:
It is noteworthy that the peak of the industrial catches – in the late 1990s/early 2000s – coincidentally aligns with the start of the recovery of many well managed stocks. This point of recovery has been documented previously and particularly relates to the recovery of large numbers of stocks in the north Pacific, the north Atlantic and around Australia and New Zealand, and mostly to stocks that are assessed by analytical models. For stocks that need to begin recovery plans to achieve sustainability, this most often entails an overall reduction in fishing effort, which would be reflected in the reductions in catches seen here. So, one could attribute some of the decline in industrial catch in these regions to a correct management response to rebuild stocks to a sustainable status, although I have not directly analyzed the evidence for this. This is therefore a positive outcome worth reporting.
This opinion piece originally appeared on SeafoodNews.com, a subscription site. It has been reprinted with permission.
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