These fisheries are even fishier than they smell.

A new study released this week called Wasted Catch: Unsolved Bycatch Problems in U.S. Fisheries reveals the nine dirtiest fisheries in the United States. It’s a dirty bunch indeed, the waste between them accounting for nearly half a billion wasted seafood meals in the U.S. alone.

Culled by Oceana, the largest international organization for ocean conservation, the fisheries are ranked based on bycatch—the amount of unwanted creatures caught while commercial fishing. Combined, they’re responsible for 50 percent of reported bycatch nationwide.

At the dirtiest fishery, Southeast Snapper-Grouper Longline Fishery, 66 percent of the animals caught are discarded—a number that includes more than 400,000 sharks in just one year. Close behind is California Set Gillnet Fishery, where 65 percent of animals caught are thrown away. The other seven dispensaries, spanning from coast to coast, are death traps for thousands of sea organisms each year. (Read the full list here).

“We’re allowing the capture and death of whales, dolphins, porpoises, turtles, and more,” Dominique Cano-Stocco, campaign director for Oceana tells The Daily Beast. While it’s technically a pro-ocean conservation organization, Oceana stresses that it’s pro-fishing too—but the safe kind. In the interest of bringing in huge quantities, commercial fishing techniques have turned grisly. “Gillnets,” or as Cano-Stacco refers to them “walls of death” are nets that can be as long as two miles. Meant to capture fish by the gills (hence the name), they snare anything from sea turtles to dolphins. “Trawls,” which Cano-Stacco has nicknamed “the bulldozers of the ocean,” are long nets that are dragged along the ocean floor, taking no prisoners in their path. “No matter if you’re looking at animal conservation, ecosystems, or just waste in general—at all nine fisheries, it’s a bad story,” she says.

With wide-reaching nets, catches are unintentionally trapping and killing thousands of unwanted bait. It’s a problem that is crippling the efforts of ocean conservationist nationwide. “If we don’t clean up these particular fishing gears then we’re continuing to throw away millions of pounds of fish every year as waste,” says Cano-Stacco. “It’s absurd.”

The gut-wrenching data, retrieved from the National Marine Fisheries Service, exposes bycatch as the dark and deadly underbelly of commercial fishing. “It’s still the largest threat to maintaining fish populations and ecosystems,” says Cano-Stacco. While scientists and the government (NOAA) have known about bycatch for a long time, their efforts to combat it have not been effective. “We’ve made great progress in the fight against this, but not enough.”

For the ocean conservation community it’s the knowledge that the senseless deaths could be avoided that is most infuriating. Banning gill nets and trawls, enforcing a system of accurate counting, and capping the number of waste, has the potential to completely change the world of commercial fishing.

As it stands now, the commercial fishing industry is eclipsing even the most advanced efforts to preserve the ocean’s natural habitat and protect endangered species. Cano-Stacco, for one, hopes that the study highlights not simply the problem, but the urgency for a solution. “If you don’t get bycatch under control, the other government programs won’t work,” says Cano-Stacco. “If you do, you not only save the ocean, you provide a potential solution to the human overpopulation crisis in the process.”