14 October 2008

Overfishing Bluefin ~ Tragedy of the Commons

I've become especially interested in the Tragedy of the Commons recently, since so much strife results from this phenomenon -- and so much irreversible ecological destruction. Witness the extinction of the carrier pigeon and moa, saga of Easter Island, probable demise of the Mayans. Professor Jared Diamond's Collapse covers much of this terrain. Today I want to spotlight the Bluefin Tuna, an amazing fish... Historically widely spread in northern and southern oceans...Researchers are tracking these fish using a growing set of measurement and tracking tools. One especially cool example of this is TOPP -- Tagging of Pacific Predators. But increasingly these fish are being consumed by humans -- some would argue over-consumed beyond the replenishment rate or carrying capacity of the fisheries. This is big-business with fish taking first-class flights around the world to reach target markets, such as the remarkable Tsukiji in Tokyo... We need to figure out better alternatives to free-range fishing since this leads to the Tragedy of the Commons where no one has the incentive to maintain the system for the long-term and everyone exploits for their short-term benefit. Perhaps -- and I emphasize perhaps, if done thoughtfully and with a better understanding of the ecosystemic feedbacks involved -- through organized Open-Ocean Ranching we might be able to maintain and even grow global stocks, much like land-based ranching has lead to a boom in cattle and other food animal stocks. This -- in principle -- might allow us all to consume tasty sustainable sushi!


Unknown said...

Hello Joost,

Thank you for bringing the plight of the world's bluefin stocks to the attention of your readers. I feel compelled, however, to take issue with your final sentence and recommendation about open-ocean ranching as a potential solution to the problem.

By definition, open-ocean fish ranches (as opposed to fish farms) operate on a system wherein juvenile tuna are caputred from wild stocks, transferred to net-pens or similar cages in near-shore or offshore zones, and fed either forage fish(anchoveta, sardines, etc.) or a processed fish meal and fish oil pellet-based diet.

There are two major problems to utilizing this strategy as a method of revitalizing the world's bluefin stocks.

The first is the capture of juveniles. By purloining wild young rather than producing fry from hatchery broodstock, these ranches have a deleterious effect on wild populations. Every fish that they raise is a fish that never had a chance to breed in the wild. How can wild populations recover unless there are enough individuals to form a strong recruitment class and repopulate the stock?

The second point is the feed. Bluefin tuna ranches generally feed their fish raw sardines, and the fish-in to fish-out ratio (the amount of fish that goes into the rand as feed as compared to the amount of fish that comes out of it as salable tuna) in a bluefin tuna farm can be as high as 25:1. That's an astronomical number. Basically, what it means it that for every pound of ranched bluefin that we consume, we're actually eating twenty-five pounds of fish. To put that in perspective for the sushi consumer, the amount of bluefin tuna that one receives in an order of toro sashimi is usually about two or three ounces. Eat that portion of bluefin and you've actually just devoured around four pounds of fish (2.5 oz x 25 = 62.5 oz = 3.9 lbs).

Why is this a problem? It has to do with something called the trophic scale. Nutrition and protein works their way up the oceanic food chain. They start as radiant light from the sun and are photosynthesized by algae and phytoplankton. These minute plants are then devoured by algavores (zooplankton, etc) which are in turn eaten by smaller fish, which are consumed by larger fish, and so on ad naseum. The trouble is, every time the nutrition is transfered up a level in this system, there is efficiency loss. We can get "X" amount of protein from eating ten pounds of sardines, or we can get a much smaller amount by eating what just ate the sardines. When we eat bluefin tuna, we are eating at the very top of the food chain. Ranching tuna for food is similar to raising lions for meat and feeding them cattle to fatten them up. It is an inherently unsustainable operation.

For the reasons above as well as other environmental and political issues, bluefin tuna ranching is a dubious response to the scarcity issue, to say the least. Perhaps a more effective method of countering the problem would be to begin to look for alternative sources of seafood which are lower on the trophic scale and thus can provide the nutrition, protein, Omega-3s, and flavor we demand without such jaw-dropping inefficiency and collateral damage.

I would encourage all who are interested in this topic to read "Bottomfeeder" by Taras Grescoe. Also, please visit http://www.tatakisushibar.com -- the first sustainable sushi bar in the world -- no bluefin allowed.


Joost Bonsen said...

Thanks Casson for your thoughtful comment. I've modified my original post to be more cautious in my finale assertion. I hadn't intended to recommend, but rather to suggest that there are third-alternatives between over-exploitation on the one hand and complete abstinence on the other.

I do, however, disagree with your assertion that open-ocean ranches necessarily capture juveniles from wild-stocks or require inherently unsustainable feed fish. I suggest what's needed is better understanding of the ecosystem and how to effectively deal with the overall food chain.

I'm willing to concede we do not know how to do this yet.


Unknown said...
This comment has been removed by the author.
Unknown said...

Hello Joost,

Thank you for your response. Actually, the capture of juveniles from wild stocks is precisely what defines a "ranch" as opposed to a "farm." A farmed fish, such as a salmon, springs from roe inseminated by broodstock within a hatchery. A ranched fish, such as a bluefin tuna, is necessarily captured from wild stocks as a juvenile.


Unknown said...

Please note that in my above statement I am referring particularly to aquaculture techniques and terminology. I am not an expert in terrestrial farming and do not know if these terms are used in the same method on a cattle ranch or chicken farm, for example.

JacquelineC said...

Your last paragraph scares me a bit. First I have to thank you for bringing the issue to the fore.

If your premise is that terrestrial farming has been successful, that is a dangerous foundation upon which to base your hopes. You must be very careful to define what types of agriculture/farming/ranching you are saying are "successful." There are plenty of data to show the destructive results of serial depletion of farm land, high emissions, high carbon footprint of farming, especially cattle farming in big industrial farms.

If your readers might be interested in learning how to make more sustainable seafood choices at home or when dining out, please direct them to Teach a Man to Fish.

Top chefs including sustainable seafood leaders Barton Seaver and Rick Moonen, Peter Pahk, Dory Ford and more will join readers, award-winning writers and regular home cooks - sharing recipes, stories and photos. I wrap it up with loads of links to resources.

I welcome your participation and that of your readers.

Jacqueline Church
The Leather District Gourmet