From the Chickens to the Crabs - The Ripple Effect: The Fate of Freshwater in the Twenty-First Century - page 74

a mate. This haphazard procreation strategy makes it essential for oysters to be bed-
ded near one another. Once gametes connect and form a larva, it drits and uses cilia to
“swim” in tidal currents. When the larva has grown to about three hundred microns, it
extends its foot onto a hard, chalky surface and grows into a spat. The zone it prefers
is just under the water surface, which holds the maximum amount of oxygen and food
particles.
Chesapeake oysters have long been farmed by “watermen,” who used sailboats and
long metal tongs or power dredges to rake them off the bottom. Traditionally, the bay
was considered a “public fishery,” meaning anyone with a license could harvest oysters
from state-owned flats. Catch size and limits were set but not always maintained. This
led to overfishing, which wore down the population. Disease further eroded stocks.
After years of decline, oysters began to grow too far apart for their gametes to connect
regularly, and those larvae that did survive had difficulty finding hard surfaces to grow
on. The population began to crash. Today, the watermen's harvest is estimated at only
one-tenth of 1 percent of what it was in 1900.
Few species filter nitrogen from the water as efficiently as oysters. “The oyster is
pretty particular about what it eats, but it's not particular about what it filters,” Bill
Goldsboro , a senior scientist with the Chesapeake Bay Foundation, said. A single oyster
can filter about fifty gallons of water per day. A few decades ago, the Chesapeake had
enough oysters to filter the entire bay every week. Today, that same task would take the
existing population a full year.
Restoration efforts have been under way for years but have shown only glimmers of
success. Over the summer of 2009, a surprising bit of good news came from the mouth
of Virginia's Great Wicomico River . An experiment that began in 2004, using broad
beds of oyster shells that raised oyster seedlings above the sediment, resulted in a prom-
ising comeback. The experimental “oyster cities”—comprising 185 million oysters on
eighty acres of raised beds, created by the US Army Corps of Engineers—contain the
largest reestablished population of native oyster species in the world. Scientists from the
Virginia Institute of Marine Science believe the Wicomico could prove a model for re-
vivals elsewhere. The looming question for researchers, though, is disease. In 1996, a
healthy spawn of oysters in the river was eventually wiped out by disease. What happens
in the next few years will be critical to Crassostrea virginica's long-term recovery.
With all due respect to the oyster, the blue crab is Chesapeake Bay's most delectable
and famous seafood. But since 1990, the bay's blue crab stock has dipped 65 percent.
While the number of crabs in the bay has always had cyclical ups and downs, it has nev-
er before stayed so low for so long. Marine biologists say that the number of spawning
crabs dropped to 100 million in 2007 and estimate that if the population dips below 86
million, the blue crab could be doomed.