While climate change is the 800-pound gorilla of ecological issues, I don’t want it to completely dominate the conversation here. There are a lot of other issues to think about. For example, overfishing!

My friend the mathematician John Terilla says that after we had dinner together at a friend’s house, he can’t help thinking about overfishing — especially when he eats fish. I’m afraid I have that effect on people these days.

(In case you’re wondering, we didn’t have fish for dinner.)

Anyway, John just pointed out this book review:

• Elizabeth Kolbert, The scales fall: is there any hope for our overfished oceans?, New Yorker, August 2, 2010.

It’s short and very readable. It starts out talking about tuna. In the last 40 years, the numbers of bluefin tuna have dropped by roughly 80 percent. A big part of the problem is ICCAT, which either means the International Commission for the Conservation of Atlantic Tunas, or else the International Conspiracy to Catch All Tunas, depending on whom you ask. In 2008, ICCAT scientists recommended that the bluefin catch in the eastern Atlantic and the Mediterranean be limited to 8500-15,000 tons. ICCAT went ahead and adopted a quota of 22,000 tons! So it’s no surprise that we’re in trouble now.

But it’s not just tuna. Look at what happened to cod off the east coast of Newfoundland:

In fact, there’s evidence that the population of all kinds of big predatory fish has dropped 90% since 1950:

• Ransom A. Myers and Boris Worm, Rapid worldwide depletion of predatory fish communities, Nature 423 May 15, 2003.

Of course you’d expect someone with the name “Worm” to be against fishing, but Myers agrees: “From giant blue marlin to mighty bluefin tuna, and from tropical groupers to Antarctic cod, industrial fishing has scoured the global ocean. There is no blue frontier left. Since 1950, with the onset of industrialized fisheries, we have rapidly reduced the resource base to less than 10 percent—not just in some areas, not just for some stocks, but for entire communities of these large fish species from the tropics to the poles.”

In fact, we’re “fishing down the food chain”: now that the big fish are gone, we’re going after larger and large numbers of smaller and smaller species, with former “trash fish” now available at your local market. It’s a classic tragedy of the commons: with nobody able to own fish, everyone is motivated to break agreements to limit fishing. Here’s a case where I think some intelligent applications of economics and game theory could work wonders. But who has the muscle to forge and enforce agreements? Clearly ICCAT and other existing bodies do not!

But there’s still hope. For starters, learn which fish to avoid eating. And think about this:

It is almost as though we use our military to fight the animals in the ocean. We are gradually winning this war to exterminate them. And to see this destruction happen, for nothing really – for no reason – that is a bit frustrating. Strangely enough, these effects are all reversible, all the animals that have disappeared would reappear, all the animals that were small would grow, all the relationships that you can’t see any more would re-establish themselves, and the system would re-emerge. So that’s one thing to be optimistic about. The oceans, much more so than the land, are reversible…Daniel Pauly

18 Responses to Overfishing

  1. John Baez says:

    Briefly, some of the worst fish to eat are:

    • beluga sturgeon (beluga caviar)
    • Chilean seabass
    • grouper
    • monkfish
    • orange roughy
    • rockfish (Pacific red snapper, rock cod)
    • Atlantic salmon
    • shark (including shark cartilage, shark fin)
    • Atlantic swordfish
    • bluefin tuna (maguro)

    If you like these fish, don’t eat them.

    • Tom Leinster says:

      Hi John,

      I’m happy that you’re pointing this out and supplying useful information…

      …but at the same time I have a kind of impatient reaction. If you think that overfishing is a problem and want to do something about it personally, don’t mess about with lists of which fish are better or worse to eat. Just don’t eat **any** fish.

      (I don’t mean you, John, in particular. I mean anyone.)

      Sorry to make my first comment here such a tetchy one. No one likes a preachy vegetarian. And please note the “if you … want do something about it personally” part. It’s an “if”: not everyone does want to.

    • John Baez says:

      I agree with you, Tom. But I might also add that we shouldn’t eat any beef (since cattle are a ridiculously inefficient way to produce food and may cause more global warming than cars), or drive cars or use airplanes except when absolutely necessary, or have children instead of adopting them, or… many other things.

      And while some of us are blameless on all accounts, most of us are so enmeshed in activities that are ruining the biosphere that it might, perhaps, be psychologically necessary for some of us to take things one step at a time.

      Or perhaps not. In many ways it’s worse for us to carry around little lists of good fish and bad fish and feel like paragons of ecological virtue each time we go shopping, while still living in a way that’s utterly out of balance in other ways.

      The words of the engineer Saul Griffith keep echoing in my mind: “I know very few environmentalists whose heads aren’t firmly up their ass. They are bold-facedly hypocritical, and I don’t think the environmentalism movement as we’ve known it is tenable or will survive.”

      Since I don’t feel able to serve as a good example in most respects, I don’t plan to spend a lot of time here telling people how to behave. All I hope to do is coax some scientists to turn their professional energies towards worthwhile goals.

      And I think the best way to do this is not by trying to induce guilt, as in: “You should be using your intelligence to save the planet, not wasting it on cute puzzles.” I had an elementary school teacher who told us that we all owed a debt to society, and that annoyed me so much that it put me off doing anything ‘useful’ for decades! Instead, I think the right way is to show scientists that it’s fun to tackle big real-world problems: it’s more intellectually interesting and just generally cooler than anything else.

      But yeah: if you care about fish in the ocean, don’t eat them.

    • Tom Leinster says:

      Re Griffith’s statement about heads up asses, I think that personal responsibility is often overemphasized. I can’t tell whether he’d agree or disagree with that.

      What I mean is that you hear a lot of “you should do this”, “you should do that”, etc. Take out your recycling, don’t take planes. Individuals can do a certain amount, but governments can do a lot more. So yes, I’m conscientious to varying degrees about these things, but I’m not under the illusion that it’s going to make much difference.

      So that’s partly what my “if” was about. Individual actions have very limited scope, and you might feel that they’re not terribly important.

      On the other hand, many people do feel some sense of personal responsibility. And I’m a believer in “do what you can”, in some not very rigorous sense. As you say, we’re all compromised. For years I ate fish and seafood but no other animals, and I was perfectly aware that this was an inconsistent position, but the inconsistency didn’t bother me. It’s not a mathematical problem with a precise solution.

      Guilting people out rarely works, I agree. So let me explain a bit where that moment of impatience came from, which is maybe less to do with guilt and ethics than was apparent. When you’ve not eaten meat/fish for long enough, it ceases to seem like a foodstuff. It’s just not something you’d put in your mouth — like leaves or grass. And it starts to seem bizarre that anyone else would eat it. So I reacted to your list of “fish species not to eat” in the same way that I might react to a list of “grass species not to eat”. Sure, don’t eat _those_ ones, but…

      • John Baez says:

        Tom wrote:

        Re Griffith’s statement about heads up asses, I think that personal responsibility is often overemphasized. I can’t tell whether he’d agree or disagree with that.

        I don’t know. Having watched his talk online, I think Griffith’s main point is that the amount our civilization needs to change to prevent dangerous global warming is vastly underestimated by most people who haven’t thought about it hard — including most people who consider themselves ‘environmentalists’. So I think it infuriates him that some people think buying a recycled tote bag is going to solve the problem.

        What I mean is that you hear a lot of “you should do this”, “you should do that”, etc. Take out your recycling, don’t take planes. Individuals can do a certain amount, but governments can do a lot more.

        I agree. Or I might say: individuals can do a lot more when they elect politicians who make governments do more.

        So I reacted to your list of “fish species not to eat” in the same way that I might react to a list of “grass species not to eat”.

        I get it. Unfortunately I’m a pedant as well as an omnivore. So I can’t resist admitting that the main grass species I eat are corn, wheat, and rice.

        I thought a bunch about grasses when writing my temperature webpage:

        By the Oligocene, 34-24 million years ago, glaciers started forming in Antarctica. The growth of ice sheets led to a dropping of the sea level. Tropical jungles gave ground to cooler woodlands.

        What caused this? Some seek the answers in plate tectonics. The Oligocene is when India collided with Asia, throwing up the Himalayas and the vast Tibetan plateau. Some argue this led to a significant change in global weather patterns. But this is also the time when the supercontinent Gondwanaland finally broke up, with Australia and South America separating from Antarctica. Some argue that the formation of an ocean completely surrounding Antarctica led to the cooling weather patterns.

        The beginning of the Miocene, 24 million years ago, is when grasses first became common. It’s sort of amazing that something we take so much for granted — grass — can be so new! But grasslands, as opposed to thicker forests and jungles, are characteristic of cooler climates. And as Nigel Calder has suggested, grasslands were crucial to the development of humans! We grew up on the border between forests and grasslands. That has a lot to do with why we stand on our hind legs and have hands rather than paws. Later, the agricultural revolution relied heavily on grasses like wheat, rice, corn, sorghum, rye, and millet. As we ate more of these plants, we drastically transformed them by breeding. In return, they drastically transformed us: the ability to stockpile surplus grains ended our hunter-gatherer lifestyle and gave rise to cities, kingdoms, more hierarchical societies, and slave labor.

        So, you could say we coevolved with grasses!

        Indeed, the sequence of developments leading to humans came shortly after the first grasses. Apes split off from monkeys 21 million years ago, in the Miocene. The genus Homo  split off from other apes like gorillas and chimpanzees 5 million years ago, near the beginning of the Pliocene. The fully bipedal Home erectus dates back to 1.9 million years ago, near the end of the Pliocene.

      • Tom Leinster says:

        John wrote:

        > I think it infuriates him that some people think buying a recycled tote bag is going to solve the problem

        Right. That’s an extreme case of what I mean by overemphasis on personal responsibility. A less extreme case is flying, which seems to be the most environmentally damaging thing that ordinary people habitually do. It’s not clear to me that persuading people to cut down on their flying is really the way forward. Yes, it would reduce carbon emissions, but by any appreciable amount?

        Or perhaps I’m only saying this because I fly a lot.

      • John Baez says:

        That’s an extreme case of what I mean by overemphasis on personal responsibility.

        Well, I chose that example for a slightly different reason: not mainly because it’s an “overemphasis on personal responsibility”, but because buying a recycled tote bag is the sort of pathetically puny step that can placate people into feeling good about themselves. In fact grocery stores seem to sell these in order to placate people.

        It’s not clear to me that persuading people to cut down on their flying is really the way forward. Yes, it would reduce carbon emissions, but by any appreciable amount?

        It’s not ‘the way forward’. In a minute, I’ll list (again) what Joseph Romm thinks are the kind of steps we need to take.

        However, flying is the activity of mine that creates the most greenhouse gases — one long flight per year pretty much cancels out any other sort of conservation measures I take, like walking to work instead of driving1. So, cutting back on flying is the single best thing I can do to reduce carbon emissions — apart from, say, persuading 5 grad students to work on energy technologies intead of n-category theory. So, I’ve been turning down a bunch of invitations to give talks. It’s not hard: there are lots of math conferences where afterward I realize I would have learned more and had more fun by staying home and talking with James Dolan.

        But I know that my personal actions are only a microscopic part of ‘the way forward’. We need action on a vastly larger scale — something more like the plan that Joe Romm lays out. This is what he says we need to achieve by 2050 for the world to stabilize at 350-450 parts per million of CO2 in the atmosphere. Each “wedge” below is a way of reducing carbon emissions by 1 billion metric tons per year:

        This is what the entire planet must achieve:

        Here are additional wedges that require some major advances in applied research to be practical and scalable, but are considered plausible by serious analysts, especially post-2030:

        • 1 of geothermal plus other ocean-based renewables (i.e. tidal, wave, and/or ocean thermal)
        • 1 of coal with biomass cofiring plus carbon capture and storage — 400 GW of coal plus 200 GW biomass with carbon capture and sequestration
        • 1/2 wedge of next generation nuclear power — 350 GW
        • 1/2 wedge of cellulosic biofuels for long-distance transport and what little aviation remains in 2050 — using 8% of the world’s cropland [or less land if yields significantly increase or algae-to-biofuels proves commercial at large scale].
        • 1 of soils and/or biochar– Apply improved agricultural practices to all existing croplands and/or “charcoal created by pyrolysis of biomass.” Both are controversial today, but may prove scalable strategies.

        That should do the trick. And yes, the scale is staggering.

        Note: For those who prefer terawatts, 1000 GW=1 TW.

        1 Of course, walking is good for other reasons: it gives me exercise, and it makes me happy in lots of ways, while driving makes me less happy.

  2. John Baez says:

    But, since this blog is supposed to focus on how scientists can help save the world, I must admit that overfishing is a problem where scientists seem to have tried very hard to alert people of a big problem, and people have gone right on marching deeper into that problem.

    So what more can scientists do? My only thought is that we may need economists, game theorists and psychologists to suggest ways to break out of the ‘tragedy of the commons’ in a situation where there’s not a powerful enforcer.

    • Mark Meckes says:

      I was surprised when, a couple years ago at a math conference, I talked to some mathematicians about overfishing who seemed never to have heard of the issue. What’s more, they were surprised to be told that very simple population models, of the type we often teach in basic ODEs classes, have a critical level of fishing/hunting/harvesting, below which the species survives indefinitely and above which it goes extinct.

      • John Baez says:

        That would be surprising to me too, except that as I start talking more and more about ecological issues to my colleagues, I discover more and more how little some of them know, even about things in the news. I think we should put a positive spin on this and say: there are many opportunities for academics to explain the science of ecology to their colleagues — and if we do this in a nice and non-preachy way, while making it clear how devastatingly important this information is, there’s a chance they’ll pass some of this knowledge on to their students, which can have a big multiplier effect.

        For example, maybe one of those mathematicians will talk about overfishing the next time they teach basic ODEs.

        In fact, I definitely will do this, thanks to you!

        I want to develop some courses on ‘green mathematics’ when I get back to UCR, but as you suggest, a lot of this stuff could easily be worked into existing courses. We might as well teach applications that actually matter: many of our students are unlikely to actually spend much time solving ODEs, but some of the implications of these ODEs might stick with them.

  3. Amitabha says:

    Some idle thoughts: Is there any way of replenishing the fish stocks in the ocean? Such as identifying fertile regions and making them out of bounds in alternate years? Or actively growing certain kinds of fish in some regions and then letting them out? Perhaps such initiatives have been already tried and failed?

  4. Florifulgurator says:

    Amitabha, it looks things are not that easy. Once a complex system (like fish food webs) has switched into a new state it is hard to get it back to the old state.

    Latest news:

    Phytoplankton in retreat

    Marine phytoplankton have a crucial role in Earth’s biogeochemical cycles, and form the basis of marine ecosystems. [...] Daniel Boyce and colleagues [Boris Worm et al.] now put these results in a long-term context by estimating local, regional and global trends in phytoplankton biomass since 1899, based on a range of sources including measurements of ocean transparency with a device known as a Secchi disk, and shipboard analyses of various types. What emerges from the records is a century of decline of global phytoplankton biomass. [...] Trends in most areas are correlated significantly to increasing ocean warming, and leading climate indices.

    Cited from:

    • Editor’s summary, Phytoplankton in retreat, Nature, July 29, 2010.

    The scientists found that the average global phytoplankton concentration in the upper ocean currently declines by around 1% per year. Since 1950 alone, algal biomass decreased by around 40%, probably in response to ocean warming — and the decline has gathered pace in recent years.

    “Clearly, 40% is a huge number,” says Paul Falkowski, an oceanographer at Rutgers University in New Brunswick, New Jersey. “This implies that the entire ocean system is out of steady state, slowing down.”

    Cited from:

    • Quirin Schienmeir, Ocean greenery under warming stress, Nature, July 28, 2010.

    Lovelock has long warned of this, cf. e.g. The Revenge of Gaia: With warming oceans the thermocline aquatic layer extends from tropical waters (which actually are “blue deserts”) towards the poles. The thermocline blocks nutrients from deeper waters to reach surface waters. So, less phytoplankton. Not only bad for the fish. Worse, it is yet another amplifying feedback in the climate system.

  5. John Baez says:

    Amitahba wrote:

    Some idle thoughts: Is there any way of replenishing the fish stocks in the ocean? Such as identifying fertile regions and making them out of bounds in alternate years?

    Florifulgurator wrote:

    Amitabha, it looks things are not that easy. Once a complex system (like fish food webs) has switched into a new state it is hard to get it back to the old state.

    I think this assessment is overly pessimistic, though the news of declining phytoplankton, if confirmed, is incredibly important.

    Consider this:

    Marine-protected areas can help threatened fish to make a rapid comeback and also lead to sustainable fishing and leisure revenues, according to a team of Australian researchers at James Cook University in Queensland.

    Writing in Current Biology, Garry Russ and his colleagues looked at how the creation, in 2004, of the world’s largest network of marine protected (no-fishing) areas covering over 20% of the Great Barrier Reef Marine Park, has affected fish stocks in these regions. The team totted up the density of coral trout at 3 inshore and 5 offshore reef regions, in each case comparing a no-fishing zone with an adjacent fished area.

    They found that in the two years after the reserves were first established the fish populations have surged. In every location tested (except one which was affected by severe coral bleaching) the coral trout population density was between 57% and 75% higher. And this is due, say the researchers, to a population increase inside the reserve rather than a decline in fish stocks in the fished areas outside the reserves.

    The results are important because flourishing fish populations inside the reserves have a tendency to “spill-over” into the adjacent waters, helping to contribute to the long-term sustainability of reef fisheries.

    “Our results,” concludes Russ and his colleagues, “provide an encouraging message that bold political steps to protect biodiversity can produce rapid, positive results for exploited species at ecosystem scales.”

    Or this:

    SAN DIEGO–When fisheries have plummeted or collapsed, one approach to fix the situation is to set up a marine reserve where fishing is banned. The idea is to provide relief to stressed fish stocks by providing safe habitat where fish can reproduce, and then spread out. But banning fishing when a fishing industry is already struggling can be controversial. Yesterday and tomorrow, at two sessions here at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW), researchers presented new data that marine reserves help fish recover.

    Jennifer Caselle, a biologist from University of California, Santa Barbara, provided a local example of success. In 2003, the state of California set up a network of 12 marine reserves near Los Angeles and banned fishing in more than 488 square kilometers. By monitoring the area before and after, Caselle and her colleagues found that over 5 years there were 50% more blue rockfish and other species targeted by fishing inside reserves than outside, and that their biomass was 80% higher. There was no change in species that people don’t eat, suggesting that fishing restrictions were responsible for the recovery.

    George Bush created marine reserves totalling 505,757 square kilometers. We need more of these: right now, less than a tenth of 1% of the ocean is protected, versus 12 percent of the world’s land (according to some estimates).

  6. [...] You might also want to kick into the subject by reading about the decline in fish occurence: ->elizabeth kolbert on overfishing on Azimuth -> randform post about fish consumption and [...]

  7. wolfgang says:

    >> some intelligent applications of economics
    I think it would already help to end subsidizing the fishing industry
    see e.g. http://www.worldwildlife.org/what/globalmarkets/fishing/subsidies.html

  8. Limiting overfishing (even without the tragedy-of-commons-effect) is harder than one might think, since 90% of sea fish is eaten by people in poor countries for whom this is the only source of protein (i.e. agriculture can produce only carbohydrates in relevant quantities).
    Btw., the “learn which fish to avoid eating” in the last sentence has no href attribute.

  9. Now that the link works, I went there and saw
    “okay to eat: … tuna … dolphin safe”.
    This is disputed: See http://southernfriedscientist.wordpress.com/2009/02/16/the-ecological-disaster-that-is-dolphin-safe-tuna/.

  10. John Terilla says:

    Also, in today’s NYTimes (about Greenberg’s new book “Four Fish”)


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