Maryland’s oyster sanctuaries will continue to provide a refuge from harvest, at least through next year, after Gov. Larry Hogan on Thursday allowed legislation barring any changes in the protected areas to become law without his signature.

The Hogan administration had sided with the state’s watermen in opposing the measure, which passed late last month. But the General Assembly, heeding pleas from environmentalists, gave the sanctuary protection bill enough votes to override the governor’s veto had he chosen to exercise it. Legislative leaders put it on Hogan’s desk March 29, and legislation becomes law after six days when there is no action by the governor.

Watermen had lobbied the Hogan administration to revisit the 2010 decision by former Gov. Martin O’Malley to expand the state’s network of sanctuaries from 9 percent of the remaining oyster habitat to 24 percent. The state Department of Natural Resources in February released a draft plan that would have shrunk the overall sanctuary area by nearly 1,000 acres, or 11 percent. It would have declassified all, or portions of, seven of the state’s 51 protected areas, while creating three new ones and expanding four existing ones.

Watermen said they wanted to open some sanctuary areas to try “rotational harvesting,” a technique developed in Virginia under which batches of oyster reefs are only allowed to be worked every few years, easing harvest pressure. The watermen had pledged to invest public funds allotted to them for oyster management in replenishing the reefs and restocking them with hatchery-spawned oysters.

But the plan drew fire from environmentalists, who contended the sanctuaries were vital to preserving and rebuilding the Chesapeake Bay’s depleted oyster population. They shouldn’t be touched, activists argued, until the state completes an assessment lawmakers ordered last year of the bivalve population and the impact of the annual commercial harvest. The DNR has until December 2018 to deliver that study, though officials have said it could be finished sooner.

When the sanctuary bill received final approval in the Senate late last month, Natural Resources Secretary Mark Belton issued a statement accusing lawmakers of acting on behalf of “special interest groups” to “upend” the work of the 24-member Oyster Advisory Commission he had appointed last year. That group, about half of its members representing or sympathetic to the oyster industry, has been meeting since July and discussing possible changes to the state’s management of its sanctuaries, its public fishery and restoration efforts.

Belton said the legislature’s vote “demonstrates a disdain of the commission’s progress and for science itself.”

Shortly after the bill’s passage, Robert T. Brown, president of the Maryland Watermen’s Association, said he didn’t intend to ask the governor to veto the bill, since the votes appeared there to override. He complained that lawmakers were “kicking the can down the road” on doing something about the uneven performance of the state’s sanctuaries.

“You’ve got maybe 20 percent that are doing good, another 30 percent that are just holding their own and rest of them are failures,” Brown argued.

But Alison Prost, Maryland director of the Chesapeake Bay Foundation, saw it differently.

“The legislature reaffirmed that Maryland should be cautious in any changes to oyster management,” she said in a statement Thursday. “We have so few oysters left, we can’t randomly increase harvesting, especially on sanctuaries. Those areas are our insurance policy for the survival of oysters in the Chesapeake.

“This bill simply reiterates what the legislature decided a year ago,” Prost added, “that a scientific stock assessment of oysters be completed before we make any major changes in our oyster management policies.”