Cover Image: February 2009 Scientific American Magazine See Inside

Using Chaos Theory to Revitalize Fisheries

There are fewer fish in the sea than ever. Complexity theory, argues mathematician George Sugihara, provides a counterintuitive way to revitalize the world's fisheries















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Others think the future is not nearly so gloomy. “It’s very dependent on where you are,” comments Ray Hilborn, a professor of fisheries management at the University of Washington. The U.S., Canada and some other developed countries have cut fishing rates, and the future looks brighter, he says. But Asia and Africa lack effective fisheries management, and even European countries have failed to agree on solid management plans. Fisheries in those regions are in far greater peril, Hil­born states.

The practical implications of Sugihara’s work are clear. Current fishing regulations usually have minimum size limits to protect smaller fish. That, Sugihara maintains, is exactly wrong. “It’s not the young ones that should be thrown back but the larger, older fish that should be spared,” he explains. They stabilize the population and provide “more and better quality offspring.” Laboratory experiments with captive fish back up Sugihara’s conclusions. For instance, David Conover of Stony Brook University found that harvesting larger Atlantic silversides from his tanks over five generations produced a population of smaller individuals.

Sugihara has also shown that populations of different fish species are linked. Most regulations consider each species—sardines, salmon or swordfish—in isolation. But fishing, he says, is like the stock market—the crash of one or two species, or a hedge fund or mortgage bank, can trigger a catastrophic collapse of the entire system.

Sugihara has also used his combined experience in ecology and finance to work on new kinds of fisheries management schemes. One is the notion of tradable “bycatch” credits. Bycatch refers to the turtles, sharks and other animals that fishing fleets do not seek but catch accidentally. In the tradable bycatch credits plan, fishing boats could be allocated a certain number of credits. As they used those credits, they would need to stop fishing or buy more credits on the open market. As the bycatch increased, the number of outstanding credits would fall, and their price would increase. Fishing boats would thus have financial incentive to minimize their bycatch—because by doing so, they could keep fishing longer.

Sugihara’s work on fisheries has not met with universal acceptance. Roger Hewitt, assistant director of the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center in La Jolla, remarks that Sugihara’s work is “a bit disconcerting” to people in fisheries management. “In fisheries, the classical approach is to model populations based on first principles. We know how fast [individual fish] are growing, how fast they are reproducing, how old they are when they mature, how many babies they have,” Hewitt explains. “George’s approach is an entirely different one. He looks at past behavior to see if he can predict future behavior.” In a crude sense, Sugihara does not need to know about growth rates, reproduction
or mortality.

Barry Gold, leader of the marine conservation effort at the Gordon and Betty Moore Foundation in San Francisco, describes Sugihara’s analytical tools as “important for understanding how we manage fisheries.” But he thinks that Sugihara’s analysis needs a real-world test: “Until it’s in the field and we see how the fishing industry responds to it, we won’t know how it’s going to work.”

Partly in response to Gold and others about the lack of convincing field tests, Sugihara is now negotiating with fishing industry groups to try to put his work into practice. “Once you’ve stopped imagining that the world is a watch, that it’s extremely predictable, you can make relatively good short-term forecasts,” he states. “I have a lot of faith in human ingenuity. But the first step is acknowledging the reality.”



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  1. 1. sidneyholt 01:54 PM 1/29/09

    I wonder what fishing technology could be used to ensure catches are only of youger fish? Sidney Holt

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  2. 2. eco-steve 10:13 AM 2/3/09

    Perhaps the answer is to put randomness back into fishing : If we banned fish shoal detection technology, fishermen would go back to trawling around at random. So this would ensure that some shoals of both young and old fish would survive to maintain populations. As captains would certainly object that this would waste engine fuel, an alternative answer would be to enforce no-go zones to reintroduce a little chaos into the system?

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  3. 3. glen hemerick 09:33 PM 2/3/09

    http://www.google.com/search?hl=en&q=hi%2C+tuesday+sept+5%2C2006%2C+i+released+lincoln+city+winter+marine+phytoplankton+culture+from+mo%27s+pier+at+51st+st+%2Clincoln+city%2C+or%2C+usa%2C+into+your+&btnG=Google+Search&aq=f&oq=
    http://www.google.com/search?hl=en&q=hi%2C+tuesday+sept+5%2C2006%2C+i+released+lincoln+city+winter+marine+phytoplankton+%3B++you+will+see+fish%2C+seals++whales&btnG=Search
    http://lh6.ggpht.com/__54z_BnhQCc/SI-hXf1huSI/AAAAAAAAAas/lNGd63sStxM/F17-Returning+to+Lincoln+City.jpg http://images.google.com/images?gbv=2&hl=en&q=lincoln+city%2Coregon++fish&btnG=Search+Images
    http://images.google.com/images?gbv=2&hl=en&q=+oregon+whales&btnG=Search+Images



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  4. 4. EloiHelper in reply to sidneyholt 06:40 PM 2/5/09

    Could be possible with a bit of thought. Doing hook & line baitboating near floating aggregation devices in the eastern tropical pacific would tend to take the smaller yellowfin, and without bycatch. It would also tend to be more labor-intensive and less fuel-intensive, important since fuel will now get scarcer forever. Mexico's Cantarell oilfield is crashing and Mexico won't be a petroleum exporter 5 years from now.

    Admittedly, this is based on the peculiarities of one species, but perhaps learning and taking advantage of such behavioral quirks is what it will take.

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  5. 5. rcvestal 09:15 AM 2/7/09

    Instead of banning areas to fish or making more laws or complicated bycatch rules ... why not tell fishermen to only keep fish of certain relative sizes - those around the 50 - 75 percentile range (maybe - don't know if this is a good number to capture a proper fish maturity). Then, spend the money to educate everyone as to why this needs to be so. The result is at the markets, public opinion would keep marketers and the public from trading in certain sizes.
    In the ocean, the small fry will be left to grow and the largest will be left to give stability - and enough numbers in the "catchable" range will slip by to become big fish.
    Now, this is sustained with public opinion and not with tax dollars to patrol and check up on fishers. And it doesn't rely on fishers only since they can only sell certain sizes.
    Will there still be a "black market"? Sure, but it will not be illegal, so if a few of the "wrong" sizes are sold, that will satisfy that small demand (at a higher price - but most wont deal in those fish due to the greater uncertainty over the ability to sell.

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  6. 6. eco-steve 07:05 PM 2/9/09

    Restricting catches of small fish has one major drawback. Fishermen throw the small fish overboard, where they simply die because they have suffered from lack of oxygen for so long. Using bigger net meshes is better, as the small fish can theoretically escape. But as fish have no fear of nets, do they try to escape through the mesh from the accustomed safety of the shoal?
    Enforcing quotas is unpopular worldwide, but it does work in Norway...

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  7. 7. John F. Caddy 05:10 AM 2/11/09

    The article by Paul Raeburn in your February issue explains how mathematician George Sugihara discovered that fishing big as opposed to small fish is bad. Ive been advocating that perspective in publications for decades*, based on my former experience as Chief of Marine Resources for FAO, especially for Mediterranean fisheries which since the second WW have been dominated by targeted harvesting of juvenile bottom fish. Few of these survive to maturity, but then these are/were apparently protected by refugia, which for the Mediterranean are rocky, untrawlable areas along the narrow shelf edge. The EC is now getting the Mediterranean message, and considering closure of areas in the NE Atlantic where large cod congregate (I mean mature cod  I doubt that any large cod are left in the North Sea). This strategy has worked (up to a point) in the Mediterranean. Until the last decade, fisheries for juveniles despite a lack of quota control, mostly seemed sustainable. That they are apparently no longer so, is probably less because of targeting juveniles, but due to the combined influence of relentless fishing, land runoff and habitat destruction; all described in the Mediterranean fisheries literature.

    Sincerely,

    John F. Caddy, Aprilia, Italy.

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  8. 8. John F. Caddy 05:11 AM 2/11/09

    The article by Paul Raeburn in your February issue explains how mathematician George Sugihara ‘discovered’ that fishing big as opposed to small fish is bad. I’ve been advocating that perspective in publications for decades*, based on my former experience as Chief of Marine Resources for FAO, especially for Mediterranean fisheries which since the second WW have been dominated by targeted harvesting of juvenile bottom fish. Few of these survive to maturity, but then these are/were apparently protected by ‘refugia’, which for the Mediterranean are rocky, untrawlable areas along the narrow shelf edge. The EC is now getting the Mediterranean message, and considering closure of areas in the NE Atlantic where ‘large’ cod congregate (I mean mature cod – I doubt that any large cod are left in the North Sea). This strategy has worked (up to a point) in the Mediterranean - until the last decade, fisheries for juveniles despite a lack of quota control, mostly seemed sustainable. That they are apparently no longer so, is probably less because of targeting juveniles, but due to the combined influence of relentless fishing, land runoff and habitat destruction; all described in the Mediterranean fisheries literature.

    Sincerely,

    John F. Caddy, Aprilia, Italy.

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