Aug. 29, 2011— -- Today, on the sixth anniversary of Hurricane Katrina, Louisiana and Mississippi are battling a sharp decline in the oyster population, which may not recover until 2013 now that a two-year influx of fresh water has killed off millions of the mollusks.
After the BP oil spill in 2010, water was diverted out of the Mississippi River to keep the oil away from coastal wetlands. In the process, freshwater flooded into oyster hatcheries, disrupting the delicate saline balance required for oysters to survive. When saline levels get too low, algae die, eliminating the oyster's food supply.
And if it weren't already enough that the Gulf Coast had been hammered by the largest oil spill in U.S. history as well as record drought, oyster farmers got hit again in May after rain and snowmelt had caused the Mississippi River to rise higher than it had in 70 years.
The Army Corps of Engineers opened the Bonnet Carre Spillway, located west of New Orleans, to divert rising Mississippi River floodwaters from the city. Soon after, they also opened the Morganza spillway, diverting water away from both Baton Rouge and New Orleans, and adding even more fresh water to oyster grounds.
"This year we'll produce about 50 percent of our traditional in-shell oysters," said Mike Voisin, CEO of Motivatit Seafoods, which typically produces about 20 million pounds of in-shell oysters.
During a typical oyster season, which starts in September in Louisiana, Voisin said the state produces a third of the nation's oysters. But this year, he estimates the number will decline from an average of 250 million pounds to about 125 million pounds.
Next year, he expects the number of oysters produced to decline even further, to 87.5 million pounds, and the price of oysters to rise.
Oyster Population Declines in Louisiana, Mississippi
The 2010 water diversion was successful in preventing Louisiana's coastline from becoming contaminated, Voisin said.
"We have 7,500 miles of coastline around Louisiana and only had 400 miles that were oiled."
But the impact that diversion had on the oysters will likely last until 2013, possibly longer.
Voisin, who also serves as chairman of the Gulf Seafood Marketing Coalition, says oyster producers east of the Mississippi River are now also investigating a mysterious substance growing on the shells oyster larvae attach to (commonly referred to as "cultch"). He believes it's due to the lack of harvesting in the area after the BP oil spill.
An oyster mortality study conducted in August of 2010 and published this year found an estimated 77 percent of the oysters in the Breton Sound basin off the Louisiana coast died.
In Mississippi, the oyster population had huge losses, especially in the western Mississippi Sound, which houses most of the commercial reefs.
"From our preliminary assessment it's pretty severe," said Scott Gordon, shellfish bureau director at the Mississippi Department of Marine Resources. "There's no denying the freshwater flooding did have an impact on the oysters."
Mississippi's restoration efforts will eventually make an impact, he said, but probably not for another 18 to 24 months, the time it takes for oysters to grow. Currently water salinities are back to normal, and the state will continue cultivating cultch plants, providing oyster shells or limestone for the oyster larvae to attach, using $3 million in restoration funding.
In Louisiana, however, water salinity continues to be a problem.
Alligator farmer Stephen Sagrera, Louisiana Wildlife and Fisheries Commission chairman, said the oyster population has been "severely hurt" by the extra freshwater, and the 7-member commission will take up the issue Thursday when it sets dates for the upcoming oyster season.
"We just have to get the right salinity in the waters," he said, acknowledging, "That's up to mother nature.