CAMBRIDGE – Captain Doug West made figure-eights in the Choptank River as a fire hose washed a 5-foot pile of oyster shells over the side of the Robert Lee. The spot where the shells sank was mapped on a laptop for future reference.
On this bright September morning, the shells carried 2.6 million young oysters, or spat, into the water.
It is just a fraction of the estimated 1 billion spat that the Robert Lee has added to the Chesapeake Bay’s waters in the last 10 years and that, in turn, is just a fraction of the billions more needed.
But officials hope to meet that need — and keep the Robert Lee busy — with a recently announced $11 million expansion of the Horn Point Oyster Hatchery in Cambridge. The expansion, set to be completed by early 2009, will allow Horn Point to raise up to 1 billion spat a year, making it the largest oyster hatchery on the East Coast, said Don Meritt, director of the hatchery.
The expansion is a key goal of the Oyster Recovery Partnership, a non-profit coalition of state, federal and private groups, working to rebuild a healthy oyster population in the Chesapeake.
“It makes it so that we can actually make a difference in the bay,” said Donald Boesch, president of the University of Maryland Center for Environmental Science, which runs the hatchery.
The oyster is critical to the bay’s health, filtering excess nitrogen, phosphorous and sediment from the waters. But diseases, over-harvesting and habitat destruction have cut today’s oyster population to an estimated 1 to 2 percent of historic levels.
“It’s a totally collapsed fishery. It’s almost been destroyed,” said Gerald Winegrad, a former state senator who now teaches environmental policy at the University of Maryland and raises oysters at his Annapolis home.
The Chesapeake 2000 agreement, developed by experts from across the bay watershed, listed increasing oyster biomass in the bay tenfold by 2010 as a key goal for restoring the health of the bay. But only 9 percent of that goal had been met by 2005, according to one report.
The Oyster Recovery Partnership, using oysters raised at Horn Point, is leading the effort to bring Maryland oyster populations to a level with both environmental and economic benefits.
“We are just trying to kick-start nature to where it can take off,” said Eddie Walters of the partnership.
But to reach the new hatchery’s goal of 1 billion spat per year, “a lot has to go right,” Walters said. Environmental factors can have a huge impact on oyster recovery work: The drought, for example, cut the number of spat raised at Horn Point this year to roughly one-third of last year’s record 350 million oysters, mainly due to water-quality problems.
“It’s a real battle,” Walters said, but one worth fighting.
“The more oysters in the Chesapeake, the cleaner the bay for my children and the next generation,” he said.
At the hatchery, oysters are induced into breeding by slowly raising the water temperature. The resulting microscopic, free-swimming larvae are transferred into towering, cylindrical 10,000-gallon tanks. There, they are fed several species of brown and green algae that are raised in a cooled greenhouse and automatically piped to the tanks.
After about two weeks, the larvae search for a place to anchor themselves and grow into spat, which resemble tiny oysters. They are moved to setting tanks, where the spat attach themselves to empty oyster shells.
When they are dumped into the bay’s waters, each shell is speckled with dozens of tiny spat that can grow into adult oysters.
But the hatchery is hampered by a lack of setting tanks. With more tanks, more spat could have been planted, said Chris Markin, a hatchery research assistant.
The expansion will solve that problem, adding 52 circular tanks 12 feet in diameter on a dock over the water. Once complete, the Robert Lee will use a crane to hoist steel cages of spat-covered oyster shells directly out of the tanks and onto its deck.
Still, recovery of oysters in the bay is by no means guaranteed. Only about 25 percent of spat planted in the bay’s waters are likely to reach harvestable size, said Ken Paynter, director of the Marine-Estuarine Environmental Sciences Program.
“While the program been going on for about 10 years, we are only starting to grasp all the environmental factors that can affect the oysters,” Paynter said.
Of the oysters that reach market size, many are harvested by watermen. In some bars, sediment from runoff or low dissolved oxygen content may kill almost all the spat planted.
“Oyster restoration is going to remain to be a challenge,” Boesch said. “It’s not going to solve the problem, but it will definitely help.”
The more than 1 billion oyster spat put in Maryland waters have greatly increased oyster and other animal life where they have been planted, but because of the immensity of the bay they have not yet created a huge increase in the total amount of oysters, Paynter said.
“Some of the old-timers say if you live long enough you see them come and go three times in your lifetime,” said Walters, a fourth-generation Kent Island waterman. “But now we have so many problems. It’s tough.”