An estimated 53,000 sea turtles are killed each year by shrimp fisheries in the United States and that could be too many if four main protected species are to survive, according to a lawsuit filed Wednesday.

The nonprofit group Oceana filed the lawsuit and claims the National Oceanic and Atmospheric Administration, the National Marine Fisheries Service and U.S. Department of Commerce have failed to put together evidence of why that number of turtles can be killed each year without threatening the survival of the species. The suit was filed in the U.S. District Court for the District of Columbia.

“Fifty-three thousand dead sea turtles is just way too many,” said Amanda Keledjian, marine scientist with Oceana.

Not only are there tens of thousands of loggerhead, green, leatherback and Kemp’s ridley sea turtles killed each year in the country’s shrimp fisheries, including along the Gulf Coast, but more than 527,000 turtles are estimated to be taken up by shrimp trawls before being released.

At the heart of the lawsuit are allegations that NOAA and associated federal agencies under the Department of Commerce were wrong in the Shrimp Biological Opinion, which anticipates the incidental killing of 50,000 sea turtles each year through shrimping.

The suit claims the federal agencies don’t require monitoring to come up with the estimate of how many turtles are killed. Instead, agencies rely on the amount of fishing that is taking place combined with an assumption of how many boats are in compliance with the use of turtle excluder devices or trawl times.

“They’re not basing it off of real observed takes (of turtles),” Keledjian said.

Although NOAA does have a monitoring program where observers travel on shrimp boats to look for turtle captures, Oceana said it is insufficient to make any determinations.

“The Southeast shrimp trawl fishery is allowed to catch and kill the highest number of sea turtles in the country, more than all other U.S. Atlantic fisheries combined, yet only 1 percent of its fleet has been monitored for sea turtle bycatch in recent years,” according to an Oceana news release.

“Their observer coverage is so low, they can’t get usable numbers,” Keledjian added.

A spokesperson for NOAA said the agency would have no comment because it involves pending litigation.

The number of allowable turtles to be taken in a fishery is supposed to be set at a level that federal agencies can show won’t damage or hamper the recovery of a species under the Endangered Species Act.

The lawsuit states the agencies failed to explain why killing 50,000 sea turtles each year won’t have an impact on recovery, while in other fisheries the level of impact is much lower and doesn’t take into account a cumulative effect of turtles killed by shrimp fisheries and other fishing, like scallops or long-line.

Turtle excluder devices, or TEDS, as well as limiting how long a trawl can be pulled are intended to either allow turtles to escape or bring the nets out of the water before captured turtles are drowned.

In addition, the lawsuit said, the federal agencies used baseline information on turtle populations that doesn’t take into account possible reduction from the 2010 Deepwater Horizon oil disaster and doesn’t set out any enforceable limits to how many turtles are killed.

Keledjian said the Shrimp Biological Opinion developed by the federal agencies also doesn’t take into account other factors such as climate change.

The lawsuit is asking the court to decide that the Shrimp Biological Opinion be thrown out and the federal agencies be told to do it again with more complete information.

Follow Amy Wold on Twitter, @awold10.