Overfishing is a major problem for the ocean's ecological health. But an even bigger problem may be the sheer volume of commercial bycatch -- the deadly capture of non-target species and ocean wildlife during the fishing process. Inadvertently trapped in nets, non-targeted dolphins, whales, and various fish species are sometimes brought to port, or more often, simply thrown overboard at sea, dead or dying. "Anything can be bycatch," said Dominique Cano-Stocco, campaign director at Oceana, a non-profit dedicated to protecting the world's oceans. "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. Bycatch also represents a real economic loss when one fisherman trashes another fisherman's catch." According to a new report from Oceana, some estimates put global bycatch as some 40 percent of all the world's seafood haul. That's more than 63 billion pounds of wasted fish and ocean wildlife, including endangered fish and dolphin species. Policing this problem may sound near impossible -- the perpetrators high in number, disorganized, and scattered across the globe's oceans. But Oceana reports that just nine major fisheries account for roughly half the problem. According to the Oceana report, the nine major culprits are: 1. Southeast Snapper-Grouper Longline Fishery (66 percent discarded): More than 400,000 sharks were captured and discarded in one year. 2. California Set Gillnet Fishery (65 percent of all animals discarded): More than 30,000 sharks and rays as well as valuable fish were discarded as waste over three years. 3. Southeast Shrimp Trawl Fishery (64 percent discarded): For every pound of shrimp landed, one pound of billfish is discarded; thousands of sea turtles are killed annually. 4. California Drift Gillnet Fishery (63 percent of all animals discarded): Almost 550 marine mammals were entangled or killed over five years. 5. Gulf of Alaska Flatfish Trawl Fishery (35 percent discarded): More than 34 million pounds of fish were thrown overboard in one year, including 2 million pounds of halibut and 5 million pounds of cod. 6. Northeast Bottom Trawl (35 percent discarded): More than 50 million pounds of fish are thrown overboard every year. 7. Mid-Atlantic Bottom Trawl Fishery (33 percent discarded): Almost 200 marine mammals and 350 sea turtles were captured or killed in one year. 8. Atlantic Highly Migratory Species Longline Fishery (23 percent discarded): More than 75 percent of the wasted fish in this fishery are valuable tuna, swordfish and other billfish targeted by the fishery. 9. New England and Mid-Atlantic Gillnet Fishery (16 percent discarded): More than 2,000 dolphins, porpoises and seals were captured in one year.