Image courtesy of Rodale

Oceans cover 70 percent of the world's surface and host such a huge variety of life that new species are discovered all the time, and a billion people on earth depend on the oceans for their primary source of animal protein -- fish. But supplying them, along with seafood-loving Americans, Europeans, and residents of increasingly wealthy Asian nations, is taking a huge toll, not just on our oceans, but on our health, too.

The seafood industry has the benefit of operating in the middle of the ocean, far, far outside the public scrutiny that has revealed the unhealthy and destructive practices of land-based factory farms and other forms of agriculture. As a result, the industry has been able to hide some of its worst tactics for satisfying our insatiable demand for omega-3s. We consulted some Rodale authors and other experts who focus on sustainable seafood to lift the veil, so to speak, on the sides of the seafood industry you won't see on reality TV shows or at your average seafood counter.

Here are some of the surprising facts they revealed:

#1: Just 1 percent of the world's fishing ships catch up to 50 percent of the world's fish.

As with land-based agriculture, just a handful of major fishing corporations control a huge percentage of the seafood that's caught all over the world. And those big companies favor big, destructive equipment. Massive "supertrawlers," as they're sometimes called, drag huge nets -- some of which are so huge they could hold twelve 747 airplanes -- that stir up the sea floor and flush fish out of their hiding spots. The largest of these gargantuan ships, the Atlantic Dawn, can haul in 300 tons of fish every day -- that's enough to feed 18 million people one fish dinner daily, writes actor and oceans advocate Ted Danson in his book Oceana. The ship also has an onboard fish-processing facility that flash-freezes its haul so the fish are ready to ship to restaurants and grocers as soon as Atlantic Dawn pulls into port at the end of its months-long fishing trips.

Your move: Eat local.

The other 99 percent of the world's fishing fleet is made up of small and artisanal fishermen who are more conscientious about maintaining healthy fisheries. While there are small fishermen who use trawls and other destructive fishing methods, buying local fish -- like buying local meat -- allows you to grill your fishmonger about where the fish comes from and how it was caught.

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#2: Our love of shrimp may very well be killing the Gulf of Mexico.

Roughly a third of all fish pulled out of the oceans are considered bycatch, non-target species that find themselves in nets or on hooks meant for other fish. Those fish get tossed back into the ocean, dead or dying, despite the fact that some bycatch species, such as cod, are commercially valuable. Shrimp trawling is one of the biggest offenders: Shrimp trawlers in the Gulf of Mexico pull up between three and five pounds of bycatch for every pound of shrimp, says Andy Sharpless, CEO of the nonprofit Oceana and author of The Perfect Protein. "Picture three to five pounds of other sea creatures on the table with you while you're eating shrimp," he says. "It would be intolerable."

Furthermore, those trawlers, which drag their nets along sea floors looking for shrimp that live in the mud, are notorious for catching and killing sea turtles, six species of which inhabit the Gulf. All six have been classified as threatened or endangered and are protected under the Endangered Species Act. However, shrimping companies have lobbied for concessions that allow them to kill the turtles.

Your move: Don't eat shrimp.

"There's no way to eat shrimp and feel good about it," says Sharpless. Farmed shrimp, the alternative to wild, may not kill sea turtles but it's filthy, he adds. "If you're eating farmed shrimp, it was grown in a shallow pond in the coastal zone of some hot tropical country, packed with thousands of other shrimp in muddy water where fecal matter piles up," he describes. "The fish are dosed with chemicals to keep healthy while they live in these conditions. It's like a chicken farm under water."

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