Editor's note: This story is part of a series of online exclusives about natural phenomena and human endeavors we'd like to see come to an end. They are connected with the September 2010 special issue of Scientific American called "The End."

The meeting of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES (pronounced "sight-eez") this past March was a decided defeat for the Atlantic bluefin tuna. Delegates voted 72 to 43 not to restrict fishing and international trade of the tuna so prized for its sushi that stocks are estimated to be at 15 percent of their historic levels. Although dismayed, conservationists remain upbeat, because they have at their disposal other management tools that could save the species.

Those strategies belong to the International Commission for the Conservation of Atlantic Tunas (ICCAT), which actually has the job to manage tuna and tunalike species (a point argued by Japan and other opponents of a CITES trade ban). Conservationists had forged ahead with a CITES effort anyway, because "we felt that a CITES ban would be a useful part of a package of tools to help reduce incentives for going over the quota," says Rebecca Lent, director of the National Oceanic and Atmospheric Administration Office of International Affairs and U.S. commissioner for ICCAT.

ICCAT, one of many regional fishery management organizations around the world, used a different tool to rebuild Atlantic swordfish populations (pdf) last September—namely, quotas. "The most important thing was setting the quotas at the appropriate level," Lent says, so that both the fish and the fishery economy can be sustained. To help enforce those limits, ICCAT tracked international trade to find countries that were catching (and selling) more fish than they reported. And domestically, the U.S. prohibited fisheries from waters where juvenile swordfish were getting killed as bycatch.

Still, getting countries to adhere to quotas is "the hardest challenge internationally," Lent says. Catch share programs, in which regional fishery councils divvy up quota shares to fishermen, could help ease this burden. Instead of creating a "struggle over a shrinking pie, you make [fishermen into] stakeholders, and that generates an incentive to be better stewards," says Frank Alcock, director of the Marine Policy Institute at the Mote Marine Laboratory in Sarasota, Fla. In the Pacific Northwest, for example, the program helped cut halibut fishing levels by one quarter.

As for the bluefin, if ICCAT fails to manage the fish's rebuilding this year, Lent points out that CITES will vote a second time, as it often does before protecting a species, in 2013. Expectations are high, she says, because "the global awareness on these species is highly increased."

Like bluefin tuna, many species popular at the dinner table, including Atlantic cod and Chilean sea bass, share red-list status as defined by the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species. Overfishing, in fact, threatens at least a dozen other species. Five less familiar ones are:

Hammerhead Sharks
Hammerhead sharks have declined by 89 percent since 1986, a rate even more alarming than that of white sharks (79 percent) and tiger sharks (65 percent). The species, which CITES also failed to protect in March, are prized for their fins, used to make a delicacy soup. And the catch method is particularly cruel: After fishermen remove the fins they typically toss the live sharks back in the water to drown.

Russian Sturgeon
For the past three generations Russian sturgeon have been facing a double threat: the loss of spawning grounds and the overharvesting of their eggs for caviar. These insults have whittled their population down 90 percent of its level from 45 years ago and put the species on the critically endangered list of the International Union for Conservation of Nature.

Sicklefish Grouper
Sicklefish grouper may now only exist in small pockets of its former range, from North Carolina to Venezuela. The IUCN classifies the fish "near threatened" because it is sparse and is being overfished.

European Eel
The unsustainable harvest rates of European eel and diminished migration (because of dam construction around Europe) add up to a decline of at least 80 percent of the population since 1968. Restocking efforts are underway, but because the eel reproduce late in life, restoration could take several generations—60 to 200 years.

Orange Roughy
The trawling of broad swaths of ocean floor off the New Zealand coast has stripped the ocean of orange roughy. From the 1970s to 1990s, the population dropped by 80 percent, and similar to other exploited species the fish have started to aggregate in smaller regions of the sea, making them more vulnerable to fishing pressure.