Please Pass (on) the Tuna

By now, most people have read or heard about Fast Food Nation, an indictment of the modern factory farm, where cheap meat is produced at an all-too-high, hidden environmental cost. The recent emergence of swine flu has once again put the spotlight on factory farming and how the industry encourages the proliferation of disease. With that in mind, I began investigating the complementary industries of fishing and aquaculture. Taras Grescoe's Bottomfeeder: How to Eat Ethically in a World of Vanishing Seafood provides an eye-opening, informative guide to the state of the world's seafood supply, and is a must-read for anyone who eats seafood, if only for reasons of self-protection.

The oceans have long been credited with inexhaustible supplies of seafood, but a combination of industrial-age fishing techniques and a burgeoning human population has wiped out many fish stocks to levels of commercial extinction. Bottom-trawling, or dragging a net across the seafloor, essentially destroys and levels hundreds of square miles of seabed each day. Dynamite and cyanide are commonly used to stun reef fish (grouper, Napoleon wrasse); it is estimated that a square meter of coral reef is killed for every reef fish caught. Meanwhile, people have been consuming more and more seafood, from the newly affluent Chinese to the explosion of all-you-can-eat shrimp and crab specials at American chains like Red Lobster.

Grescoe introduces the concept of trophic numbers, a way to classify levels of the food chain, ranging from 1 for plankton and plants to 5 for large predators like lions or humans. Generally, eating closer to the bottom of the trophic scale is better for the environment. In a whirlwind tour around the world, Grescoe follows the supply chains of the globe's most popular seafood dishes. The bad news is, once you know the story behind that plate of pan-roasted monkfish, you will feel compelled to never eat it again. The good news is, there are plenty of alternative seafood choices which are both better for the environment and better for your health. Some of the species highlighted follow below.

Bluefin Tuna (trophic level 4.4)
Though the word "tuna" tends to evoke cans emblazoned with "chicken of the sea," the bluefin tuna could not be further from that image. A ferocious torpedo-shaped hunting machine, the bluefin can grow up to 15' in length and sprint at 50 mph. Unfortunately, the bluefin tuna is now the ocean's ultimate cash cow. Once plentiful, Atlantic bluefin stocks have declined by 90% over the past four decades to feed the demand for bluefin sushi. And despite efforts by conservationists to limit the number of bluefin caught, you can still pick up a bluefin nigiri breakfast (including the prized toro) for a mere $15 in Tokyo. Meanwhile, the long-lived tuna species (yellowfin, albacore and bluefin) tend to be dangerously high in mercury. Tuna is also commonly caught using longlining, which snags sharks, swordfish, seabirds and turtles as bycatch.

With that knowledge, I would rather cross tuna off my list of things to consume. Another option: non-longline-caught skipjack tuna (marketed as "light tuna") is low in mercury and relatively plentiful in oceans.

Shrimp (2.6)
Shrimp farming takes place in some of the world's poorest countries, and the industry has left indelible destruction on the scale of the 2004 Asian Tsunami. Like large poultry and swine operations, shrimp ponds are treated with heavy-duty chemicals including antibiotics (to prevent disease) and piscicides (to kill any competing aquatic life). The resultant pollution causes disease in natives, destroys groundwater and wipes out the livelihoods of neighboring farmers and small-scale fishermen. The effects extend to distant consumers as well; some people who believe they have allergies to shellfish are in fact reacting to antibiotic residues in farmed seafood. Wild shrimp, on the other hand, are usually caught with bottom-trawlers. For every pound of shrimp caught, another ten pounds of unwanted, dead fish are thrown overboard.

What, then, is the conscientious shrimp-lover to do? Examine your purchases very, very carefully. If the shrimp on display glisten unnaturally or taste soapy after cooking, they have probably been treated with sodium tripolyphosphate, a suspected neurotoxicant. Wild-caught shrimp are undoubtedly better for your health, but exert a huge environmental cost. That leaves only a few stocks of northern shrimp, pink shrimp and spot prawns in Canadian and northern US waters which are considered sustainable choices.

Other Good Alternatives:
Oysters and mussels (2.0) are farmed without chemicals and help clean the oceans. Small schooling fish like herring (3.2) and sardines (2.6) are low in toxins and relatively abundant. Jellyfish (2.0) have proliferated in recent years due to climate change and overfishing of top-level predators. Trout (4.4), arctic char (4.3) and barramundi (4.4) are farmed in non-polluting, contained inland systems. Farmed tilapia (2.0) and catfish (3.8) are herbivores, so they do not diminish the net supply of protein, and buying domestic products reduces the risk of antiotic residues.

When buying seafood, you should be able to make an informed choice with 3 questions. Was the fish farmed or wild-caught? If wild, what ocean did it come from and what port did it land in? How was it caught (trawl net, hook and line)? If farmed, was it farmed domestically or overseas? If overseas, in which country? Shedd Aquarium provides a handy, wallet-size card that lists recommendations for purchasing seafood. I've printed one out to carry as a reference guide. But in the end, all the knowledge in the world won't help you if your grocer, fishmonger or server does not know the source of their products. If you find someone knowledgeable and willing to answer your questions (Dirk's and the Fishguy come to mind), support their business with your purchases.