A damning report by the international conservation advocate Oceana accuses fisheries of wasting close to 20 percent of the total United States catch yearly.

The newly-released data also names nine U.S. fisheries that altogether discard almost half of all they catch and are responsible for more than 50 percent of all the country's annually-reported bycatch, the catch of non-target fish and ocean wildlife.

It's estimated 40 percent of the world's total catch may actually be bycatch, totaling 63 billion pounds per year globally and about 2 billion pounds every year in the U.S.

Titled "Wasted Catch: Unsolved Bycatch Problems in U.S. Fisheries," the study asserts that, despite some success over the last decade in stemming the amount of bycatch, the yearly killing or injuring of thousands of protected and endangered species continues to be significant problem in domestic fisheries.

"Whether it's the thousands of sea turtles that are caught to bring you shrimp or the millions of pounds of cod and halibut that are thrown overboard after fishermen have reached their quota, bycatch is a waste of our ocean's resources," Dominique Cano-Stocco, campaign director at Oceana, said in a statement.

Oceana explains that while some fishing methods are more harmful than others, open ocean trawl, longline and gillnet fisheries -- methods used by the nine fishing operations highlighted in the report -- are responsible for the majority of the bycatch in the U.S.

"Hundreds of thousands of dolphins, whales, sharks, sea birds, sea turtles and fish needlessly die each year as a result of indiscriminate fishing gear," said Amanda Keledjian, a marine scientist at Oceana and the report's author. "It's no wonder that bycatch is such a significant problem, with trawls as wide as football fields, longlines extending up to 50 miles with thousands of baited hooks and gillnets up to two miles long. The good news is that there are solutions -- bycatch is avoidable."

The report notes the bycatch problem in the U.S. is probably much worse than is known, since most fisheries don't have adequate monitoring procedures in place to record exactly what types of sea life are caught and how much is later wasted.

It's believed that with some fisheries, as few as one of every 100 fishing trips carries impartial observers to document what is catch, while many are not monitored at all.

The Oceana report's "Nine Dirty Fisheries" and the estimated annual percentage of their catches discarded, based on data published by the National Marine Fisheries Service, are: Southeast Snapper-Grouper Longline Fishery, 66 percent discarded; California Set Gillnet Fishery, 65 percent of all animals discarded; Southeast Shrimp Trawl Fishery, 64 percent discarded; California Drift Gillnet Fishery, 63 percent of all animals discarded; Gulf of Alaska Flatfish Trawl Fishery, 35 percent discarded; Northeast Bottom Trawl, 35 percent discarded; Mid-Atlantic Bottom Trawl Fishery, 33 percent discarded; Atlantic Highly Migratory Species Longline Fishery, 23 percent discarded; and New England and Mid-Atlantic Gillnet Fishery, 16 percent discarded.

Bycatch "represents a real economic loss when one fisherman trashes another fisherman's catch," said Cano-Stocco. "Reducing bycatch is a win-win for fishermen and conservationists ... By eliminating wasteful and harmful fishing practices we can restore and maintain fish populations that are essential to renewed abundance and healthy oceans."