Surveys of coastal oyster grounds have discovered extensive deaths of the shellfish, further threatening an industry already in free-fall because of BP’s oil spill in the Gulf of Mexico.
The deaths are blamed on the opening of release valves on the Mississippi River in an attempt to use fresh water to flush oil out to sea. Giant diversion structures at Caernarvon and Davis Pond have been running since April 25 on the orders of Louisiana Gov. Bobby Jindal and local officials with the consent of the Army Corps of Engineers.
For the past 82 days, about 30,000 cubic feet of water per second has flowed into coastal Louisiana, enough to fill the Louisiana Superdome, home to the New Orleans Saints football team, nearly once an hour.
“What I saw does not look good,” Patrick Banks, oyster manager for the Louisiana Department of Wildlife and Fisheries, said in an e-mail. He said he found no evidence of oil on the reefs east of the Mississippi River, but he said they “looked to be fallow reef.”
Banks dove onto reefs at Black Bay, Bay Crab and Telegraph Island, where the state is building public oyster grounds for farmers to collect baby oysters and transfer them to their private leases. Once there, they are raised to market size.
Public reefs account for up to half of Louisiana’s oyster harvest, an industry that employs about 6,000 people and is valued at $330 million.
On Thursday, Banks said oyster deaths also were found west of the Mississippi, though the surveys there are not yet complete.
Reports also are coming in about damage to private oyster grounds.
John Tesvich, chairman of the Louisiana Oyster Task Force, a state committee overseeing the industry, said the reports of oyster deaths on private leases are worrisome.
Oysters use saltwater to make their shells and need it to keep their vital membranes working properly. They can tolerate small doses of fresh water for perhaps a couple of weeks, but they will die if they suck in too much.
“The public reefs on the east side of the Mississippi — American Bay, Black bay, Breton Sound — that is where most of our seed comes from, and they might be closed for a long time,” Tesvich said.
Garret Graves, Jindal’s chief coastal aide, said the state is looking at “all adverse effects” of the oil spill on the Louisiana environment.
“BP as the responsible party is expected to pay for all of the natural resource damages associated with this spill,” Graves said. He is the chairman of Louisiana’s Coastal Protection and Restoration Authority.
Earl Melancon, an oyster expert at Nicholls State University in Thibodaux, said he has already written off this year for oyster production.
“If you lose an oyster reef, it takes three years minimum to get it back into production,” he said. “And it could take five years.”
Oyster reefs lie a few feet under the water and span the Louisiana coast. Often, farmers help build oyster grounds by dropping concrete and other hard surfaces into the water so oyster larvae can attach to them.
Most likely, the oysters that will do the best will be those close to the Gulf of Mexico, where there’s more salt water.
But those shellfish could be vulnerable to the oil, which has been washing into coastal waters since the end of April.
The Louisiana oyster spawns by releasing larvae that swim through the water and find places to sit on and grow. The oyster goes through various stages — from growing a leg to losing it, changing sexes and growing a shell by extracting calcium carbonate from the water — to the point where it is big enough to sell on the market, between two and four years old.
From now until next spring, Melancon said the big question will be whether there will be a new brood of oyster larvae planting itself on Louisiana’s reefs.
The industry already was reeling from several bad years marred by hurricanes, heavy rains and over-harvesting — a situation made worse by the oil spill and the freshwater diversions, Tesvich said.
Plus, a more limited supply could drive up oyster prices. But Banks said the industry has rebounded before.
“The good news is that we have been this low before,” Banks said. “Mother Nature is amazing and oysters can come back.”