Oysters are thriving in sanctuaries that Maryland has created across the Chesapeake Bay, but their numbers are waning in areas open to harvest, according to a highly anticipated state report.
The findings could significantly influence debate over whether the state should change course in its efforts to restore oyster populations. The Hogan administration has suggested that some sanctuaries could be opened up to watermen, either temporarily or permanently.
Maryland significantly increased the portion of the bay that is off limits to oyster harvesting in 2010. In the new report, officials at the Maryland Department of Natural Resources wrote that it's too early to know definitively whether those sanctuaries are working, but said a commission charged with evaluating state oyster restoration efforts could nonetheless consider reopening some areas to harvest.
Environmentalists criticized the report as being too heavily focused on boosting the seafood industry, rather than on protecting the bay's oyster population.
"They've written the report to support any alternative management practice the administration chooses," said Doug Myers, senior scientist in the Chesapeake Bay Foundation's Maryland office.
But one of the state's top environmental scientists said that while the report could be used to justify a reduction in sanctuary acreage across the bay, it still is supportive of sanctuaries as a tool for oyster restoration.
"It has laid out a clear commitment to continue with the sanctuaries where there's been active restoration work, and also those that seem to have performed well" at letting oysters reproduce and grow, said Donald Boesch, president of the University of Maryland Center for Environmental Science.
The report set the stage for Maryland's Oyster Advisory Commission to recommend possible changes to state restoration strategies. It is not intended to dictate state action or set future oyster policy, said Stephen Schatz, a spokesman for the natural resources department.
Among the commission's tasks is helping state officials review whether to resume a project in which state, federal and nonprofit agencies have built artificial reefs and seeded them with lab-grown oysters in a sanctuary in the Tred Avon River. State officials paused the project last winter at the urging of watermen, saying the report on sanctuary performance should guide the effort. Maryland lost out on $1 million in federal money as a result.
The Oyster Advisory Commission on Monday voted to move forward with work in an eight-acre section of the Tred Avon. The project is scheduled to eventually cover 147 acres of the river, one of five Chesapeake tributaries in which the state has committed to restoring oyster populations.
But the group recommended several conditions that would promote the use of old oyster shells, instead of stone, to build the new reefs. Watermen have expressed concerns that artificial reefs can damage boats and equipment used for crabbing and other types of fishing.
The commission recommended state officials consult more closely with local stakeholders, including watermen, in the future. And the panel also asked the natural resources department for the ability to review any projects that use stone to build reefs.
The state must inform the Army Corps of Engineers by Friday whether the federal agency should resume the work this winter. Schatz said he expects that to happen Wednesday or Thursday.
Oysters are vital to the bay ecosystem because they filter nutrients and other pollutants from the water, and their reefs provide habitats for fish, crabs and other underwater flora and fauna. They were once abundant in the bay, but their numbers have fallen to 1 percent of historic levels because of overfishing and disease.
State officials are evaluating efforts to increase the bay's oyster populations after five years, as planned. In 2010, the state significantly expanded the footprint of oyster sanctuaries in the bay, from 9 percent of oyster habitat to 24 percent.
From 2009 until 2014, oyster populations across the bay grew steadily, helped by unusually successful reproduction cycles in 2010 and 2012, according to the report. Oyster larvae float freely in the water, and whether they live or die depends on how densely reefs cover the bay floor, providing a surface for them to attach and grow.
While the number and size of oysters inside sanctuaries grew 21/2 times from 2010 to 2015, oyster bars open to harvest saw a 30 percent decline from 2013 to 2015 on average, the study found.
Researchers hypothesized that is because by 2014, the oysters outside sanctuaries that were born in 2010 and 2012 were being harvested, whereas inside the sanctuaries, the mature bivalves were helping to build new generations.
Still, they added that it's too early to come to any conclusions.
"Given the complexity of the Chesapeake Bay ecosystem, five years has not been long enough to show how oyster populations respond to the absence of harvest," the report says. "The overall, long-term behavior of sanctuaries will depend on many factors including changes in weather, water movement patterns, disease and predator/prey abundance."
State natural resources officials nonetheless suggested possible changes to oyster efforts.
In their report, they grouped reefs based on population growth, density and potential, suggesting the commission reconsider which reefs should receive state investment, which should remain as sanctuaries, and which should be open to harvesting. .
"Although five years is not enough time to fully understand the biological consequences of sanctuary management, there is justification to consider adjustments to the boundaries of the current management areas," they wrote.
Myers said that suggestion was a concern because it does not take into account the factors that make oyster bars thrive inside of sanctuaries. Those bars contain many generations of oysters that help promote breeding and foster disease resistance.
When watermen harvest oysters, they take away the largest and oldest of the oysters — those best for the gene pool, he said. Even if the sanctuaries were subject to harvesting only on a rotational basis, that could still be a significant setback from an ecological perspective, he said.
Boesch agreed that allowing any harvesting in sanctuaries could compromise their integrity.
"The idea of sanctuaries is you want to keep the survivors, the old animals, in the broodstock producing eggs and larvae," he said. "Anything that opens the sanctuary to harvest makes it no longer a sanctuary."
Baltimore Sun Media Group reporter Christina Jedra contributed to this story.