State and local wildlife experts are trying to figure out what led more than a thousand flounder, spot and pin fish to beach themselves at the Marine Corps' New River air base — and then swim away.
They believe it may be related to a popular phenomenon known in coastal Alabama as "jubilee."
The fish surfaced in shallow water Friday morning. They were lethargic, but alive.
"It's kind of strange," said Mike Sanderford, New River Riverkeeper. "It's a bunch of fish up here, but they're not dead. They're almost docile."
When he arrived, Sanderford said, the fish were lying in shallow water and allowed him to touch them before they swam away.
Representatives of the Division of Water Quality, N.C. Marine Fisheries and N.C. Marine Patrol checked on the fish along the air station's shoreline Friday morning. One expert estimated about 1,000 to 1,500 were crowded in the waterline.
But by afternoon, they were gone. The timing matched another oddity: the water's oxygen level, which veered from one extreme to the other.
"We measured the oxygen levels in the water this morning and they were very low," said Stephanie Garrett, environmental technician with DWQ. "Then two and a half hours later, they were high."
She said that might be a clue that the area saw a case of the "jubilee" phenomenon, in which thousands of live, healthy fish beach themselves.
Scientists know that a jubilee occurs when variety of factors deoxygenate the water, forcing fish to the shore.
Jubilees occur in a number of places, but nowhere as often and as regularly as on Mobile Bay's eastern shore. Jubilees usually occur during the summer, providing a free feast to locals who head to shore to gather the fish up.
"It's normal to them, they all know the conditions that are needed and go down with gigs to get the flounder," said Bianca Klein, biologist at the Air Station. "It's definitely a rarity here, though."
Only about 50 fish died, and that may not have been from natural causes.
"The flounder that were dead were the big ones," Sanderford said. "We're guessing someone came out here early this morning and started to pick out the biggest ones to take home for dinner, but wondered why they were beached and thought something might be wrong with them."