More than 200 dead sea turtles have washed ashore on North Carolina's Outer Banks beaches in the past week, an unusually high number for such a short period of time.
The strandings have pushed the toll for this year to more than 340 and have prompted an investigation by the National Marine Fisheries Service.
State and federal fisheries biologists said Tuesday they do not know what killed the turtles, but remnants of fishing nets were found on four carcasses.
Charles Oravetz, assistant administrator for the National Marine Fisheries Service in St. Petersburg, Fla., said the agency is examining the pieces of net and fishing operations at the time to see if commercial fishing contributed to the deaths.
"It's kind of unprecedented for that many turtles to wash up in North Carolina over this time period, and we're very concerned about it," he said.
Because sea turtles are protected by federal law, the agency could order changes in fishing gear or close areas to fishing. A decision on what action will be taken is expected in a few days, Oravetz said.
Most of the dead turtles were loggerheads, which are designated as a threatened species under the federal endangered species law, and a few were Kemp's ridley turtles, which are listed as endangered.
About 210 to 220 dead turtles were found last week on beaches from Oregon Inlet to Hatteras Inlet. That's more than the total of 191 stranded from January through May last year, according to Ruth Boettcher, sea turtle project coordinator for the N.C. Wildlife Resources Commission.
She said the animals were severely decomposed, making it difficult to determine the condition of turtles before they died or the cause of death. Most were immature turtles about 22 to 40 inches long.
Northeasterly winds apparently blew the carcasses from offshore waters, she said, with most washing up last Wednesday and Thursday.
Authorities were unable to determine what killed 71 turtles that washed up between April 14 and April 17 on beaches on Ocracoke and Hatteras Islands. "Those turtles were in better condition generally than this last batch, but there were no indications at all of what the cause of death might have been," Oravetz said.
The animals were apparently healthy at the time of their death, he said.
Oravetz said gill nets strung out to catch fish can hold and drown turtles when they become entangled in them.
The fisheries service will look at the different mesh sizes being used for various fish to determine if they likely conflicted with turtles.