Oyster Reproduction, Survival Rates at Highest Levels Since 1997

The Oyster Question: Scientists, Watermen, and the Maryland Chesapeake Bay since 1880 (Environmental History and the American South)
Governor Martin O’Malley Announces Oyster Reproduction, Survival Rates at Highest Levels Since 1997

Trends indicate population may be developing resistance to disease; More Marylanders looking to start up or expand aquaculture businesses

February 8, 2011 (Annapolis MD) — Governor Martin O’Malley today announced a multitude of good news for the Chesapeake Bay, Maryland’s green economy and Crassostrea virginica, the Bay’s native oyster: According to the State’s recently completed fall oyster survey, the number of spat or baby oysters in Maryland waters is at its highest level since 1997, the survival rate for young oysters is also up, and more Marylanders are looking to start up or expand aquaculture businesses.

“Even as our population stood at 1 percent of historic levels, we did not give up... and we now have exciting new evidence that — like our blue crab — our native oyster has not given up either,” said Governor O’Malley. “We now have reason to be more optimistic than ever about the recovery of this iconic species, a recovery that would further improve water quality, create green jobs and support local economies.”

“Moving forward, it is our responsibility to strengthen our restoration commitment, our enforcement actions and our investment to further to protect our future broodstock,” added Governor O’Malley, who has proposed a $25 million investment in the Chesapeake and Coastal Bays Trust Fund in his FY 2012 budget.

Since 1939, the Maryland Department of Natural Resources (DNR) and its predecessor agencies have monitored the status of Maryland’s oyster population via annual field surveys — one of the longest running such programs in the world. The survey tracks three critical components of the population: Spatfall Intensity, which measures reproduction levels (recruitment) and offers a window into future population levels; disease infection levels; and annual mortality rates of oysters.

“For more than 15 years, the State and its partners have aimed to jump-start Mother Nature by investing in building the necessary infrastructure, deploying billions of oyster spat on shell and reclaiming thousands of acres buried shell from derelict oyster reefs. Now, it seems she’s fighting with us,’ said DNR Secretary John Griffin. “These animals are proving just how resilient they can be given the right circumstances.”

The 2-month 2010 fall population assessment, which encompassed 260 oyster bars and 399 samples throughout the Bay and its tributaries, concluded on December 18. At nearly 80 spat (baby oysters) per bushel, the 2010 spatfall is the highest since 1997, and about 5 times the 25-year average of 16.

“The increased spat set is an immediate asset to Maryland’s expanded sanctuary program,” said DNR Fisheries Director Tom O’Connell. “These protected oysters will grow and reproduce, contributing more oysters to the Bay’s sanctuary and surrounding aquaculture and public fishery areas, and providing important ecological benefits such as water filtration and reef habitat.”

Eleven of the 53 oyster bars included in this index had their highest or second highest spat counts since 1985. The elevated spatfall was a coast-wide phenomenon, with other mid-Atlantic states also reporting better than average numbers.

Equally encouraging was wide distribution of spat throughout the Bay and its tributaries: While the heaviest counts were in the lower Bay’s higher salinity areas, where reproduction is typically more successful, a moderate spatfall also occurred in lower salinity areas that generally receive little to no spat sets at all. These included the upper Bay as far north as Pooles Island and the upper reaches of the Chester, Choptank and Patuxent River tributaries. Due to reduced disease pressure, oysters historically have good survivorship in these areas, some of which are now protected sanctuaries under the State’s new oyster plan.

Even more encouraging news for the beleaguered oyster is that the frequency and intensity of diseases remains low, based on December’s interim report from the Paul S. Sarbanes Cooperative Oxford Lab. Of the two diseases that have devastated populations for decades, Dermo, although still widely distributed, remains below the long-term average for the eighth consecutive year, and MSX appears to again be in retreat after an advance in 2009.

The survey indicates that oyster survivorship — the percentage of oysters found alive in a sample — was at 88 percent, the highest level since 1985, before diseases put a stranglehold on the population; this is more than double 2002 when record disease levels left only 42 percent of Maryland’s population alive. Scientists are hopeful that favorable mortality in recent years may reflect an increase in disease resistance.

“These moderate levels of natural oyster mortalities during recent years may reflect increases in disease resistances among oysters and their progeny that survived the severe disease pressures of the 1999-2002 drought,” said Chris Dungan, manager of oyster disease research at the Oxford Lab. “Those same disease-selected oysters are the parents that spawned to produce the significant spat set of 2010.”

“In this new reality, where disease mortality sometimes exceeds natural and fishing mortality, recruitment has become of singular importance,” said DNR Fisheries Service Assistant Director Mike Naylor. “While challenges remain and recovery — particularly development of disease-resistance — will take decades, if the present trend in below average mortalities continues, the combination of the great 2010 spatset and low mortality should bode well for Maryland’s oyster population and fishery well into the future.”

Last year, the State of Maryland adopted regulations to implement Governor O’Malley’s Oyster Restoration and Aquaculture Development Plan. The plan increased Maryland’s network of oyster sanctuaries — from 9 percent to 24 percent of remaining quality habitat; increased areas open to leasing for oyster aquaculture, and established a $2.2 million financial assistance program for aquaculture interests; and maintained 76 percent of the Bay’s remaining quality oyster habitat for a more targeted, sustainable, and scientifically managed public oyster fishery.

Since last fall 26 Marylanders have applied for 35 new leases to grow oysters and the State has received 27 applications for more than $2 million in available funding for start up and expansion of aquaculture businesses. Blue crab disaster funds, championed by Senator Barbara Mikulski, are being used to support this program.

“Through the steady leadership provided by Governor O’Malley, Senator Mikulski and Secretary Griffin — as well as the growing environmental stewardship of Marylanders — we are changing the face of oyster restoration while preserving our cultural heritage in Maryland and witnessing historically significant growth in our capacity to improve Chesapeake Bay waters,” said Stephan Abel, Executive Director for the Oyster Recovery Partnership. In a coordinated effort among the Partnership, the University of Maryland, the NOAA Chesapeake Bay office and DNR, over 2.5 billion hatchery produced spat have been produced and planted in Maryland’s portion of the Chesapeake Bay since 2000, and thousands of acres of buried shell have been reclaimed from derelict oyster reefs.

Since 1994, the Chesapeake Bay oyster population has languished at 1 percent of historic levels. Over the past 25 years, the amount of suitable oyster habitat has declined by 80 percent — from 200,000 acres to just 36,000 acres. Maryland’s annual oyster harvest has fallen from an average of 2.5 million bushels in the late 1960s to about 100,000 bushels a year since 2002, while the number of oystermen working Maryland’s portion of the Bay has dwindled from more than 2000 to just 550.


Press Release
Maryland Department of Natural Resources
February 8, 2011 Contact: Josh Davidsburg
410-260-8002 office | 410-507-7526 cell

The Maryland Department of Natural Resources is the state agency responsible for providing natural and living resource-related services to citizens and visitors. DNR manages nearly one-half million acres of public lands and 17,000 miles of waterways, along with Maryland's forests, fisheries and wildlife for maximum environmental, economic and quality of life benefits. A national leader in land conservation, DNR-managed parks and natural, historic and cultural resources attract 11 million visitors annually. DNR is the lead agency in Maryland's effort to restore the Chesapeake Bay, the state's number one environmental priority. Learn more at www.dnr.maryland.gov.

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