Exaggerated Claims About Over-Fishing Of The Oceans?

I was investigating peak wild-caught fish recently when I stumbled across Our Oceans Can't Survive Fishing Madness by Gareth Morgan and Geoff Simmons, authors of Hook, Line and Blinkers, an in-depth look at fishing off New Zealand. I was particularly struck by this passage.

Scientists disagree over the size of the overfishing problem. Getting reliable catch data is hard enough, data on fish populations is a lot more difficult - we can't see them, and they move around. You may recognise some of the more alarmist claims — that most large fish populations are 10 per cent of their original size and that the oceans could collapse by 2046.

[My note: They meant 2048.]

More reliable stock assessments show that around a third of all fisheries are now overfished - in a state where the annual catch is a lot less than what could have been achieved, and worse - still falling. But even this data has its problems - it is only available for a handful of fisheries, and we often don't know what the original state of the fish population was so estimating the true sustainable yield is impossible.

But what everyone can agree on is that the tragedy of the commons still exists in the global fishery, and that the only way around this problem is to manage our fisheries...

Alarmist claims? WTF? You see, I am one of the people making these "alarmist" claims. Those claims are based on a paper which appeared in Science called Impacts of Biodiversity Loss on Ocean Ecosystem Services (2006). The lead author was Boris Worm of the Department of Biology at Dalhousie University, Halifax. Here's a graph from the paper.

Fig. 3. Global loss of species from large marine ecosystems (LMEs). (A) Trajectories of collapsed fish and invertebrate taxa over the past 50 years (diamonds, collapses by year; triangles, cumulative collapses). Data are shown for all (black), species-poor (<500 species, blue), and species-rich (>500 species, red). (B) Map of all 64 LMEs, color-coded according to their total fish species richness.

Morgan and Simmons refer to "more reliable stock assessments" which show that only about a third of all fisheries are overfished, not the nearly 70% shown by the black triangles in the graph shown. What's going on here?

We get some of the story from Global Fisheries Declines Less Steep Than Earlier Reports, Study Says.

A new study by U.S. researchers says that recent estimates of declining global fish stocks, including a 2006 report predicting a general collapse by 2048 without significant changes to fisheries management, were overstated because they relied on a flawed methodology.

While earlier calculations were based on the amount of fish caught, the new report, published in the journal Conservation Biology, says calculations based on the estimated biomass of available stocks provides a more accurate assessment of the state of global fisheries. The earlier study by researchers at the University of British Columbia calculated that 70 percent of fish stocks had peaked and were now declining as a result of overharvesting, and that 30 percent of species had fallen to 10 percent of earlier numbers.

Trevor Branch, a professor at the University of Washington and lead author of the new study, says an assessment based on biomass data reveals that, at most, 33 percent have been overharvested, and about 13 percent have collapsed. While Branch said those numbers are still a cause for significant concern, he said the findings suggest that fisheries management has helped stabilize fish stocks in most regions.

It turns out there is an academic dispute between Trevor Branch (and supportive colleagues) and Boris Worm (and his supportive colleagues). We get some details from One Fish, Two Fish, False-ish, True-ish, published at the New York Times Green blog on May 1, 2011. It's worth reading because the devil is always in the details.

The new study takes issue with a recent estimate that 70 percent of all stocks have been harvested to the point where their numbers have peaked and are now declining, and that 30 percent of all stocks have collapsed to less than one-tenth of their former numbers. Instead, it finds that at most 33 percent of all stocks are over-exploited and up to 13 percent of all stocks have collapsed.

It’s not that fisheries are in great shape, said Trevor Branch, the lead author of the new study; it’s just that they are not as badly off as has been widely believed. In 2006, a study in the journal Science predicted a general collapse in global fisheries by 2048 if nothing were done to stem the decline.

OK, that's a brief review of what I've told you so far. Let's get to the nub.

The work led by Dr. Branch is another salvo in a scientific dispute — feud might be a better word — that pits Dr. Branch and his co-author Ray Hilborn at the University of Washington’s School of Aquatic and Fisheries Sciences and their allies against scientists at the University of British Columbia and their partisans.

The latest paper argues that the methodology resulting in the most dire estimates, derived from records of the amount of fish caught, is not as accurate as data from the more broadly based United Nations assessment, based on the estimated biomass of available stocks of individual species.

When the catch-based approach was applied to data on 234 global fish stocks from 1950 to 2006, it showed that 68 percent of all fisheries were either over-exploited (46 percent) or collapsed (22 percent) by the end of that period, while none were increasing.

By contrast, when an assessment is based on an estimate of biomass, it showed that 28 percent of fisheries were either over-exploited (15 percent) or collapsed (13 percent). The second method also indicated 24 percent of the stocks were increasing.

Flawed methodology? Let's look at flawed methodologies.

But Dirk Zeller, a scientist at the University of British Columbia who is on the other side of the debate, doesn’t buy all of Dr. Branch’s arguments. Yes, he said, using fish stock data is preferable to using catch data. But if reliable fish stock data is only available in developed countries like the United States or Australia — where fisheries management is reasonably well developed — what good is it in determining what is happening in the rest of the world?

Dr. Zeller said that Dr. Branch and his University of Washington colleague Ray Hilborn had taken a stand in some previous papers that “if you look at fish stocks that have formal stock assessment processes, you find that many of them — not all — are relatively healthy. That’s valid.”

“Where their argument falls down is that they extrapolate that pattern to global fisheries, and then say global fisheries aren’t doing that bad,” he said. “They totally ignore the fact that all of Asia, all of South America, all of Africa are not included.”

Dr. Zeller added that 234 stocks are a tiny subset of thousands of species currently being fished, not a sample from which one can derive broad conclusions.

Whoops! Dr. Branch and friends used a too-small sample, and then extrapolated it to the rest of the world. They couldn't include data from the ocean waters adjacent to all of Asia, all of South America, and all of Africa because it does not exist. In these areas of the world, fisheries management can hardly be said to exist, and thus there is no good data for fish stocks (as opposed to fish landings).

[Zeller's] University of British Columbia colleague Daniel Pauly, who has objected to Dr. Branch’s work on other other occasions, is blunter. “The school of fisheries around Branch and Hilborn are now contesting everything that seems to be established,” he said in an interview. “The point is not whether you use catches or estimates of biomass inferred from other data. The point is that you make proper inferences"...

“I have no argument with the point that with stocks that are well managed you can have sustainable fisheries,” Dr. Zeller said. He pointed out that he and Dr. Pauly have adjusted their online database to reflect a critique by Dr. Branch that their analysis had given short shrift to rebounding fish stocks. But he does maintain that data from catches are more applicable on a global scale than other data sets.

Perhaps you are tired of this seemingly academic dispute, so I'll cut off the discussion now and make a few remarks of my own.

When I say the world's fisheries are likely to have completely collapsed by 2048, I am not talking out my ass. I am making that claim based upon the best available science. That is not an "alarmist" claim. It is based on valid inferences from what is known about wild-caught fish landings, aka. peak fish.

But there a deeper level of perception and insight available here. Unless well-established human behaviors were to change in wholly unexpected ways in the future, we will to overfish the oceans until almost the fish species there are either commercially extinct, and therefore unexploitable—this is the more likely outcome for most species—or physically extinct, meaning gone forever.

We've got this one Earth. We've got this one set of oceans. That's all we've got. This is not an academic dispute. We're talking about the ultimate fate of humanity and most of the Earth's living organisms. Only on Planet Stupid would this debate even be taking place. Denial is not going to fix the problem. This is how Felicity Barringer—yes, that is her name—concluded her New York Times article.

Even without the aid of mathematical modeling, it is possible to predict that fish population debates themselves will remain sustainable for some time to come.

A clever ending, worthy of somebody named Felicity. If only 50%, not 33% or 70%, of the world's marine fisheries have collapsed or are over-exploited, it appears to be only a matter of time before humankind "achieves" 100% of the fisheries, so what difference does it make? So don't call Worm's or Pauly's views of the oceans alarmist. None of this would be happening if humankind could take its collective head out of its collective ass.

No doubt Felicity is right. Humans will be debating "fish population" questions right up to the time when such debates make no difference at all because at that point, catching a fish in the ocean will be a cause for much celebration.

Comments

[Alex]

i trully believe that even the scariest "doom and gloom" predictions cannot be called "alarmist" anymore

there always be people who will personally benefit from denial of obvious to anyone who has even a grain of reason (that is knows basic math and is not delluded by ideology of any particular belief-system - i know a rare find :))

even in theory the chage from denial into dealing with the problem will not begin to manifest until the ecosystem collapse and most of humans die out from extreme weather events, hunger, war over resources and desease

this is a certainty - the fact that in science we cannot use such language does not change anything - yes it ain't over till it over - but for all practical purposes the probability of averting the complete collapse of ecosystem and fossil fuel civilization may be called "non-existent"

thanks to dave we have a steady supply of evidence to corroborate the non-existance of that probability