By Benjamin Alexander-Bloch, NOLA.com | The Times-Picayune
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on July 13, 2013 at 5:00 PM, updated July 14, 2013 at 1:03 AM
It’s difficult to talk about Louisiana seafood these days without the BP oil spill working its way into the conversation. It wasn’t that long ago, after all, that television screens were filled with high-def images of fouled coastal marsh and angry fishermen forlornly staring at their idled fleet.
But some scientists and fishers say it remains impossible to gauge the 2010 spill’s precise environmental and biological toll. Asked about a 15-percent drop in the statewide oyster harvest in the two years following the spill, experts say the spill definitely continues to be a potential factor, but is only one of several.
Perhaps as damaging as the oil and the temporary closures of thousands of acres of Gulf waters in the wake of the disaster three years ago, they say, was the millions of gallons of fresh Mississippi River water that flowed into the Lake Pontchartrain Basin east of the river in 2010 and 2011. Oysters, essentially immobile and unable to withstand the torrents of fresh water, bore the brunt.
A closer look at the preliminary data from the Louisiana Department of Wildlife and Fisheries reveal wide variation from area to area. But in terms of oyster production, the Lake Pontchartrain Basin east of the Mississippi River saw the worst of it.
Before the oil spill, Louisiana regularly led the nation in oyster production, with the Lake Pontchartrain Basin traditionally the state’s most productive harvest grounds.
From 2002-2009, the Pontchartrain Basin averaged 7.2 million pounds of oyster meat annually. But beginning in 2010, that production took a nose dive – falling to 2.6 million pounds that year, then to 2.4 million pounds in 2011 and, finally, to 1.8 million pounds in 2012.
Overall, just in 2011 and 2012, oysters in Pontchartrain Basin saw a 71-percent drop compared to the 2002-09 average.
While oyster production showed an increase in the Terrebonne Basin, east of the Mississippi River, the decline in the Lake Pontchartrain Basin was so pronounced that it pulled the overall statewide numbers down in all three years.
“It’s been really down. ŠNormally we always put 400 sacks on the trucks but the last three years or so, we have only been able to put on 150, 130, 140 sacks,” said Shawn Assavedo, an oyster harvester in Pontchartrain Basin out of eastern St. Bernard Parish. “That’s exactly what it’s been since they opened that siphon.
“That freshwater, it goes into Lake Borgne and it has killed a lot of oysters there, really a massive amount of oysters.”
Now the measly haul of oysters in Pontchartrain Basin often is dwarfed by the expanse of the 18-wheeler trucks’ beds.
Brad Robin Sr. talks about how one of the most production areas in the country for harvesting oysters is still struggling to recover.
Brad Robin Sr., a fellow St. Bernard oysterman who typically harvested out of Lake Borgne, said that his old stopping grounds have had “zero percent come back.”
“There is no life left there,” Robin said. “The east side of the river is way down and still trying to recover, trying to get some sort of normalcy out of it all.”
But the fears is that the decline east of the river could continue for an extended period: The Pontchartrain public harvesting grounds in the Breton and Chandeleur sounds provided the majority of the oyster seed that harvesters transplanted to grow oysters in private leases across the state.
“Our public reefs on the east side of the river, that was our mother seed ground,” said John Tesvich, chairman of the Louisiana Oyster Task Force. “That is basically wiped out right now.”
The freshening of the water
While the oil spill is an easy fall guy – and many scientists continue to study its impact, often in secrecy for future oil-spill litigation – scientists and some fishers also point to the Mississippi River diversions in 2010 and 2011 as major culprits for the plummeting oyster haul.
“Freshwater is the biggest killer of oysters in the world,” said Greg Voisin, an eighth-generation oysterman who helps run his family business, Motivatit Seafoods, in Terrebonne Parish.
Ken Brown, a Louisiana State University biologist, said he and his colleagues haven’t seen any major effects from the oil on adult oyster mortality rates, but when fresh water dilutes salinity levels “below 10 parts per thousand, and especially if you get below 5 parts per thousand, then oysters have problems.”
Hoping to keep the oil that was spewing from BP’s Macondo well away from Louisiana’s fragile inshore marshes and estuaries, the state in 2010 ran the Davis Pond and Caernarvon river diversions at full speed for several months to push the oily Gulf waters away. The diversions did appear to help drive out some of the oil but they also dropped salinity levels in much of that Pontchartrain Basin to levels unsustainable to oysters.
Then in 2011, when Mississippi River levels in New Orleans approached the 17-foot flood stage because of heavy rainfall in the Midwest, the Bonnet Carré Spillway west of the city was opened from early May through mid-June, further freshening the basin.
That fresh water that poured from Bonnet Carré into Lake Pontchartrain eventually pushed into the surrounding waters of Lake Borgne and the Mississippi Sound.
The state had anticipated the impact from the Bonnet Carré opening. The Louisiana Wildlife and Fisheries Commission chose to open oyster reefs within portions of the Pontchartrain Basin area before opening the spillway, allowing oyster fishers to take oysters from those grounds and move them to private leases in higher salinity areas.
Oysters thrive when the salinity is 15 parts per thousand, about half the salinity of seawater. They struggle when it falls below 10 parts per thousand and die off when it dips below 5 parts per thousand.
Parts of Pontchartrain Basin fell to less than 3 parts per thousand during periods of 2010 and 2011, according to state and federal data.
Oyster growth problems
Because fresh water diversions carry so much sediment – they often are envisioned as land builders – the diversions in 2010 and 2011 also buried or at least partially covered much of the cultch in Pontchartrain Basin, according to a Wildlife and Fisheries assessment.
Oysterman Brad Robin Jr. explains how small pieces of chopped concrete made from the slabs of flooded Hurricane Katrina homes helps oysters grow.
Cultch is the broken stones and oyster shells that form the reefs upon which oyster larvae attach and grow into adult oysters. Lose the cultch, and the oysters have nothing to latch onto.
Also, in some areas east of the river, much of the oyster shell was covered with an unidentified algae that seems to have prevented oyster seed from taking hold on the reefs.
Some oyster fishers pointed to that algae as an indicator that the oil spill had ruined their crop, but scientists say it also might have been created by the excess nutrients in the river water that poured into the basin.
While nutrients carried by freshwater play an important role in the high productivity of the Gulf systems, they also bring algae blooms, which consume oxygen and create “dead zones” with fish- and oyster-killing low oxygen levels.
Tesvich said he and others also worry about the quality of that river water and whether problems with oyster reproduction on the existing cultch could be tied to the oil.
“Was there some sort of industrial waste or agricultural runoff in that river water?” he asked. “Or is it something from BP in addition to the river water that is causing something? There are a lot of things we just don’t know about these oysters coming back.”
But it wasn’t all bleak where the oyster harvest is concerned.
State Wildlife and Fisheries Department data show that in 2011 the Barataria Basin, to the west of the river, harvested 23 percent more oysters than its pre-spill average and then, in 2012, harvested 44 percent more.
And because the price of oysters continued to rise, the Wildlife and Fisheries numbers show that Barataria oyster fishers earned about $18 million in 2012 – about 116-percent more than they had earned on average between 2002 and 2009.
In 2012, the average price statewide was about $3.70 per pound at the dock, or about 30 percent above the pre-spill average of about $2.80 per pound.
Nonetheless, Al Sunseri, who owns P & J Oyster Co. with his brother Sal, thinks the Wildlife and Fisheries numbers are wrong when it comes to the amount of oysters that have been harvested in Barataria the past few years.
“I’m not a scientist, but I just have some common sense,” Sunseri said. “There is something going on, because we are not seeing the oysters come back like they always did.”
Still, Mitch Jurisich, who harvests a large chunk of the oysters in Barataria, recently said that the last few years have been “the best crop in our family’s history.”
“Jurisich and others in the area did extremely well,” Tesvich acknowledged, but he added that other parts of the Barataria “have been having trouble because of so much fresh water.”
And then there is Terrebonne Basin, which was hopping the past few years, according to the state landings data and discussions with oystermen.
A basin that on average harvested 2.3 million pounds of oysters between 2002 and 2009, Terrebonne produced 4.4 million pounds in 2011 and 4.3 million pounds in 2012. That’s about an 85-percent increase.
Most of that increase in Terrebonne Basin actually could be tied to decreases elsewhere, as oystermen relied on that area to cover declines. For instance, the number of trips oyster fishers took in the basin grew from an average of 7,814 between 2002-2009 to 16,928 trips in 2012 – a 116-percent increase.
“Our oysters being available, it allows the areas east of the river to rest and go through whatever cycle they are going through,” Voisin said. “You have to utilize the resource here when it’s not there, and there when it’s not here, and that’s just the way that we’ve be doing things throughout history.”
Despite the 15-percent drop in statewide oyster production the past couple years, the state’s oyster fishing industry as a whole doesn’t appear to have fared too bad financially.
Because the price per pound has risen since the spill, the overall amount earned by oyster harvesters across the state in 2011 and 2012 actually rose by about 10 percent compared to the pre-spill average, according to the Wildlife and Fisheries’ at-the-dock price and landings data.
Also, the state’s 2012 basin-by-basin data and the statewide 2012 data from the federal Fisheries Service remain very preliminary. Often, the federal data rise by several million pounds when finalized.
The Fisheries Services is expected to release more official 2012 statewide catch numbers this fall.
The conventional wisdom is that two or three years after a major fresh water event, oysters will grow back strong. Often in history, it creates a boom crop. With less salinity, for example, there often are fewer predators that eat the oysters.
So some oyster fishers are waiting, fingers crossed, hoping that in the next few years there will be a bumper season.
Count Assavedo among them. Assavedo is among those oystermen plowing ahead in the Lake Pontchartrain Basin, spending money to put down new cultch in the hope that better days are ahead.
It’s a risk he feels he has no choice but to take.
“If it is not fresh cultch material, you are not getting anything. But my new stuff out there, that I laid down, it seems to be doing good,” Assavedo said. “The oysters stuck to it and are growing. I haven’t lost any of them yet. ŠI just hope that continues.”
Wayne Gordon, an employee with P&J Oyster Co., loads up a delivery truck on Oct. 28, 2010, with the first load of oyster that Pete Vujnovich harvested near Port Sulphur since the closure of area 13 back on May 20, 2010.
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Special thanks to Richard Charter