Maryland blue crabs scooped up off Tilghman Island. (André Chung/for The Washington Post)

There are more spawning-age female blue crabs in the Chesapeake Bay than there have been in at least 28 years, a sign that efforts to help the species withstand natural population swings are working.

However, an annual survey of the bay’s crab population found that there are fewer crabs overall in the bay than there were a year ago — about 455 million, down from 550 million.

That is because tides and currents carried less larval crabs up the estuary. The number of adult male crabs also fell.

“Despite the modest number of young crabs, the total population remains stable and the number of spawning-age females — a major scientific benchmark for the health of the species — rose,” said David Blazer, director of fishing and boating services for the state Department of Natural Resources. “This is testament to the state’s adaptive and effective management of the fishery.”

Crab season began April 1 and continues through the fall. The survey results likely foreshadow a strong first half of the crab season for Maryland watermen — until midsummer, they will be catching many of last season’s abundant juveniles that have matured enough to be harvested.

But into the fall, crabs that meet the harvest size minimum could become scarcer, state natural resources officials said.

Chris Moore, senior scientist for the Chesapeake Bay Foundation, called the results “a mixed bag” that show signs of resilience in the crab population, but also cause for concern.

“The low number of juveniles suggests we need to keep in place the suite of crab management regulations first agreed to in 2008 by Virginia and Maryland,” he said. “We also must maintain federal funding for critical crab management programs, such as underwater grasses restoration.”

Gov. Larry Hogan’s administration acknowledged last month that it might be open to revising catch limits, such as a midsummer increase in the minimum crab harvest size. Wednesday’s release of the population survey results launches an annual process of reviewing the regulations and whether they can or should be changed.

Blazer said any such changes “will only be considered after we receive input from all parties involved.”

Bay advocates meanwhile are also pressing against President Trump’s budget proposal that calls for elimination of the Environmental Protection Agency’s Annapolis-based Chesapeake Bay Program. That office coordinates cleanup efforts across the bay watershed’s six states and the District of Columbia.

The regulations established in 2008 focused on boosting the population of spawning-age female crabs and, among other things, restricted Virginia crabbers from dredging up pregnant females during their winter hibernation. A target population of 215 million spawning females was established.

The 2016 survey results mark the second time since then that the target has been exceeded, with an estimated 254 million spawning-age female crabs in the bay. That was a 31 percent increase over 2015, a jump similar to the one reported when the target was last achieved in 2010.

Blue crab numbers are naturally prone to swings because of the species’ complex and short life cycle. After being spawned in Virginia bay waters, larval crabs spend the earliest stage of their life in the Atlantic. Wind and weather carry them up the bay to grow and spend the winter burrowed in mud. The following season, they emerge and resume growing, with an average life span of two years.

The state Department of Natural Resources and the Virginia Institute of Marine Science have conducted the annual crab population survey since 1990. It involves sampling numbers of hibernating crabs dredged from the mud.

A group of scientists that sits on the Chesapeake Bay Stock Assessment Committee will analyze the survey results and advise fishery managers in Maryland and Virginia who decide on harvest policy changes.

For the first time in years, Maryland’s longtime crab fishery manager, Brenda Davis, will not be part of the process. Natural Resources Secretary Mark Belton fired her in February without explanation.

Watermen said they had been frustrated with Davis for what they saw as inflexibility in loosening harvest rules.

The Baltimore Sun