Imagine ordering bluefin tuna at your favorite luxe Japanese restaurant. (We know you wouldn’t because the species is in serious decline, but let’s just pretend.) The waiter serves your exceedingly expensive dinner—in 2013, a single 489-pound bluefin fetched $1.76 million—and you take a moment to appreciate the artful arrangement of the sashimi. Then you pick up the plate and casually toss it out the restaurant window.

That is essentially what the United States fishing industry is doing every year, wasting $1 billion worth of fish caught as bycatch, according to a report released Thursday by Oceana, a nonprofit that works to protect the world’s oceans. The waste represents 20 percent of the industry’s 2012 revenues.

Oceana analyzed bycatch data collected from the National Oceanic and Atmospheric Administration and then determined the market price of the discarded fish.

“Bycatch, or the capture of non-target fish and ocean wildlife, remains one of the biggest threats to the health of ocean ecosystems, contributing to overfishing and the decline of fish populations around the world,” wrote the report’s lead author, Amanda Keledjian, estimating that 2 billion pounds of fish are abandoned by American commercial fishermen annually.

Including bluefin tuna.

Oceana estimates that in the Southeastern U.S. fishermen threw overboard $3.4 million worth of bluefin in 2010, while California fishermen threw away half a million dollars' worth. Other valuable fish left off the dinner table were Pacific halibut ($58 million), sea trout ($45 million), Atlantic sea scallop ($32 million), red snapper ($27 million), and summer flounder ($7.2 million).

Related America Tosses Nearly 20 Percent of All the Fish We Catch

Commercial fishing is a hard and dangerous profession, so why would anyone willingly treat their meal ticket as trash?

“One of the main reasons for discarding fish is that the fish might be too small to keep, poorer quality than something else they might bring onboard, or that fishermen have reached their yearly quota for that species,” Keledjian said in an email. “In all of those cases, modifying fishing gear or changing the way fishermen use existing gear would help keep those fish in the water.”

Unwanted catch—along with dolphins and other marine mammals—also get swept up in the giant nets deployed by fishing trawlers to catch a specific type of fish.

“In terms of mechanization, or industrial-scale fishing operations, it definitely depends,” said Keledjian about trawlers’ contribution to bycatch. “Sometimes mechanization could increase efficiency and reduce waste, and sometimes it just creates a derby 'race to fish' situation.”

The report said the U.S. fishing industry could cut bycatch and the damage it does to marine ecosystems by adopting other countries’ practices. Those include setting quotas for bycatch, levying a tax on bycatch, and creating an eco-labeling program for fish caught sustainably.

In other words, it depends on what you put—or don’t put—on your plate.