Oysters appear to be thriving in much of the expanded network of sanctuaries Maryland set up six years ago to protect them from commercial harvest, according to a long-anticipated review that the state Department of Natural Resources released over the weekend. But the overall size of the bivalve population elsewhere is shrinking, the review reveals, as watermen scoop up the larger shellfish in waters open to them.

The DNR report cautions that it’s too soon to draw firm conclusions about how the state’s 51 oyster sanctuaries are doing since their number and area were greatly increased in 2010. Even so, state fisheries managers suggest that some of them could be re-opened to commercial harvest -- something watermen have been pressing the state to do.

The DNR released the draft report Sunday night, less than 24 hours before its Oyster Advisory Commission is scheduled to renew debate about whether to go ahead with a federally funded oyster restoration project in the Tred Avon River. The 23-member panel split on the issue when it met last week, with watermen and elected officials representing them questioning the merits of sanctuaries. Several panel members said then that they wanted to see the DNR report before taking a vote.

The 945-page report draws on DNR’s oyster reef sampling to detail conditions in each sanctuary and on every oyster reef open to harvest in Maryland’s portion of the Bay. While noting that information is incomplete about some areas, the report says that the sanctuaries are generally fulfilling the expectations laid out when the state’s policy was overhauled under former Gov. Martin O’Malley, a Democrat.

In 2010, the O’Malley administration overhauled state regulations to expand state waters designated as sanctuaries, making 9,000 acres of the “best” remaining oysters bars off limits to harvest. The other 27,000 acres’ worth of productive oyster habitat remained in the public fishery. The law and rules also were changed to permit much more private leasing of the Bay for oyster aquaculture. Prior the overhaul, oyster sanctuaries in the Chesapeake were small, and often on barren bottom where oysters did not grow well.

As part of the 2014 Chesapeake Bay Watershed Agreement, Maryland and Virginia pledged large-scale oyster restoration efforts in five waterways each. Maryland identified three tributaries of the Choptank River to start – Harris Creek, the Little Choptank River and the Tred Avon. Maryland finished its $26 million restoration in Harris Creek last year, but the other two are not complete.  If carried out according to the joint federal-state restoration plan, the total investment in those three waterways is projected to be about $44 million.

Fueled by two years of decent reproduction, the commercial harvest in the reduced public fishery area more than doubled, to nearly 417,000 bushels a few years ago. But it has begun to decline since then. Oystermen, whose ranks have doubled since 2010, have pressed to reopen some sanctuaries. A delegation persuaded the Hogan administration last winter to seek a halt to reef construction in the Tred Avon until the DNR’s five-year review of its management shift was complete.

The DNR report says that over the last decade, oyster “biomass” -- a measure of their size and number -- has generally increased throughout Maryland waters, whether in fished or sanctuary areas. During that time, all the bivalves have benefited from low disease mortality and from good reproduction in 2010 and 2012.  Since then, disease die-off has remained low, but reproduction has been spotty across Maryland waters. While sanctuary oysters have continued to grow absent harvest pressure, the biomass in fished areas has begun to decline, the DNR found, a dip it attributed to watermen harvesting the larger, older oysters.

“Because these large, older oysters are not harvested in sanctuaries, the biomass continues to rise each year,” the report notes. “As these older, larger oysters produce the most eggs, reproductive potential in sanctuary areas also continues to rise.”

While stressing that five years is too short a time frame to fully understand how the sanctuaries are doing, the DNR report nevertheless says that “there is justification to consider adjustments to the boundaries of the current management areas.” That justification appears to come from the review’s finding that nearly half the sanctuaries have had mixed results or sparse oyster populations.  It suggests reopening at least portions of some sanctuaries that have poor habitat or very low densities of oysters, but only after re-seeding them with hatchery-reared oysters and possibly rebuilding reefs.

“If the ultimate goal is to have more oysters in the water, then some areas that are currently sanctuaries could contribute to this goal and provide economic and cultural benefits to fishing communities, particularly if these areas are managed in a way that balances harvest with continuous investment to maintain oyster populations in the area,” the report says.

Natural Resources Secretary Mark Belton says he’s open to trying new management approaches in those areas, such as “rotational harvest,” where oysters could only be taken every three or four years to allow the reefs to be replenished through natural reproduction or re-seeding.

The report suggests funds for such fishery-supporting restoration work could come from license surcharges, oyster bushel taxes, leasing portions for aquaculture, or unspecified “private-public partnerships.” The state already spends more than $1 million a year on replenishing reefs regularly harvested by watermen, using a $1 per bushel tax on the harvest plus about $1 million annually in funds shifted to DNR from the Maryland Department of Transportation.

The U.S. Army Corps of Engineers, which is handling the Tred Avon restoration, has asked the state to give it an answer by Friday, Aug. 5 on whether to resume work in the river. After building 16 acres of reefs last year, the Corps agreed to the Hogan administration’s request to delay construction of another eight acres. Army officials say they need to know if it's a go by the end of the week, or there may not be time to issue the contract to get the work done by this fall or winter.

But Belton said Friday he doesn’t want his advisory commission to feel pressured to make a quick recommendation.

“I would rather not worry about a deadline,” he said. “It needs to be the right decision.”

While saying the panel’s input will inform DNR’s decision, Belton added that his boss, Gov. Larry Hogan, has the final say.

Under the previous administration, nearly half the commission was comprised of scientists and environmental advocates. The newly constituted commission under Hogan, a Republican, includes more members of industry than in the past.

Some watermen and their supporters also asked Belton to look into whether all or part of the Tred Avon could be reopened to commercial harvest, possibly designating another tributary for the large-scale restoration effort. Belton declined to say Friday what he had learned about that. A spokesman for the Army Corps said last week that under an oyster restoration master plan jointly prepared by federal and state agencies, “sites where Corps of Engineers funds have been invested are to be preserved by the State of Maryland as permanent sanctuaries.”

Others have warned that if the state backs out of the Tred Avon restoration or even delays much longer in going forward, the Baltimore District of the Corps could transfer its remaining federal oyster restoration funds – about $2 million in all – to the Norfolk District for use in Virginia oyster restoration projects. The Baltimore District already shifted $1 million to Virginia earlier this year after the Tred Avon project was delayed.

“The Oyster Advisory Commission is deadlocked right now, and if we’re deadlocked after Monday night, where does that leave us?” asked Bill Goldsborough, senior fisheries scientist for the Chesapeake Bay Foundation and a member of the panel.

The Annapolis-based environmental group issued a statement Friday saying that based on other data released before this five-year review, including a report last week by the National Oceanic and Atmospheric Administration, “all indications are the large reef projects, including the Tred Avon, are working.”  The foundation called on the Hogan administration to let the project proceed.

“Not … giving the Corps an answer by the 5th is letting the decision make itself,” Goldsborough said. “It potentially jeopardizes the whole funding stream.”