NOTE: This is a guest post from Ken Hinman, President of the National Coalition for Marine Conservation.

Like many Americans, I was first introduced to the blue marlin by Ernest Hemingway in his classic 1952 novella, The Old Man and the Sea, which chronicles an existential battle between an old Cuban fisherman and a great fish longer than his boat.

Reading the story then, I could only imagine how much that fish weighed, but today I know the real-world record for a blue marlin caught on rod-and-reel is an astounding 1,500 pounds. And they get a lot bigger than that. The blue marlin is, by any measure, a magnificent fish; an unparalleled combination of size and speed that, coupled with a powerful sword-like bill, make it one of the ocean’s top predators.

Blue marlin and other billfish, a family that includes four species of marlin as well as the smaller sailfish and spearfish, are the lions, tigers and wolves of the sea, wild creatures as awe-inspiring as any animals on earth. They sit at the top of the ocean food chain, where they play the critical role of maintaining balance and diversity in marine ecosystems.

Unfortunately, although billfish have few natural predators, they are among the most threatened fish in the sea. Man, after all, is the most dangerous predator of all, since we are limited only by the limits we set for ourselves. Here in the United States, where fishermen revere and protect billfish, we’ve set limits. On the high seas, however, commercial overfishing by foreign fleets has reduced billfish populations to a mere fraction of what they were just decades ago.

According to a recent global assessment by the International Union for the Conservation of Nature (IUCN), three species of billfish are in serious trouble. The IUCN, which maintains the well-respected Red List of Threatened Species, classified blue marlin and white marlin as “vulnerable” to extinction, while striped marlin was assessed as “near threatened.”

The key to recovery of billfish is to reduce commercial fishing pressure, says the IUCN. As it happens, Congress is now considering legislation that would strengthen current U.S. law and enhance conservation of billfish worldwide.

The Billfish Conservation Act of 2011 (S. 1451 and H.R. 2706), introduced this summer, would prohibit the sale of all species of billfish (swordfish are not included) in the U.S., with an exception for traditional fisheries within Hawaii and the Pacific islands. Sale of Atlantic billfish is already prohibited, as is striped marlin in California. But we are the number one buyer of foreign-caught fish, importing about 1,335 metric tons – an unthinkable 30,000 Pacific marlin and other billfish – each year for sale in our mainland restaurants and seafood markets. The Billfish Conservation Act, if passed by Congress, would take marlin off the menu in the mainland U.S.

Throughout history, animals once offered for sale are no longer. Societies determine that certain species need to be protected from the demands of commerce. The reasons may be social, economic, ecological or all three. It doesn’t happen overnight; it takes many decades, even centuries. Today, we’ve reached that point in history with billfish.

It’s a natural progression. Hemingway hunted big marlin and hung them on the dock. Today, the billfish anglers I know don’t “catch” the fish at all, but let them go alive, modifying their gear to make sure every released fish survives. Some say the tipping point occurred in 1958, off Cape Hatteras, when my late friend Jack Cleveland caught a blue marlin he guessed weighed somewhere between 300 and 400 pounds. When he shocked everyone by letting it go, it was the talk of the docks up and down the coast, the first known voluntary release of a big blue. Fifty years later, it’s the angler who lands a billfish who’s got some explaining to do.

Marlin are hard to find and even harder to catch. Just as hard to find are bills like The Billfish Conservation Act. It’s picking up broad bipartisan support in Congress, as well as the backing of the environmental and sport fishing communities, because it’s good for the fish and good for the economy. U.S. commercial fishermen don’t target billfish. Sales of imports amount to less than 0.1% of our seafood industry. Consumers have plenty of sustainable alternatives. The catch-and-release recreational fishery, while leaving a negligible salt water footprint, contributes thousands of jobs and many millions of dollars to the national economy.

Santiago, the aging fisherman in The Old Man and the Sea, pays homage to his mortal adversary. “…Never have I seen a greater, or more beautiful, or a calmer or more noble thing than you, brother.” With this bill, we can show our respect while sending the message that the future of these majestic fish is not for sale.