A recent survey delivered mixed news for Chesapeake Bay blue crabs and the watermen who harvest them.

The Virginia Marine Resources Commission released the results of the 2017 Winter Dredge Survey for blue crabs on April 19. The survey showed a 31-percent increase in adult female crabs in the Chesapeake Bay watershed compared to last year’s survey, from 194 to 254 million.

It is the highest recorded level of adult, spawning age females in the history of the survey. These females are crucial to maintaining a viable crab stock in the bay.

“We have found a statistical relationship basically saying that the more females you have, the more juveniles you will have the following year,” said Virginia Institute of Marine Science Professor Romuald Lipcius.

The annual survey has been conducted by VIMS and the Maryland Department of Natural Resources since 1990. Dredges sample 1,500 sites throughout the bay from December to March. Lipcius said the winter conditions discourage the crabs from moving, which improves the accuracy of the survey.

“It’s probably the best survey of a crab fishery anywhere in the world,” he said. “In most other ecology surveys, we’re often pretty happy if we can get 30 to 50 percent (confidence). The way we’ve been able to knock that down is because we sample 1,500 stations every year.”

The total blue crab population for the survey was 455 million. This is the 11^th-highest total ever recorded, but is also approximately 18 percent less than the previous 2016 survey.

The biggest concern is that juvenile crabs dropped from 271 million to 125 million, the fourth-lowest level ever recorded and just 20 million more than the lowest ever in 1992.

Crab reproduction is vulnerable to fluctuations year-to-year, and juveniles are at the mercy of several factors, such as environmental changes and natural predators.

“A lot of fish like to eat those young blue crabs,” Lipcius said.

He said the blue crab life cycle also has a phase outside the bay, when new larvae leave the watershed and return in approximately a month.

“That part of the life cycle is mostly beyond our control,” he said.

This reinforces the need for a good stock of females. Crab harvest was reduced by 10 percent across the bay in 2014 to boost dangerously depleted female stock, and bay fishery managers have since focused on conserving juvenile crabs and spawning-age females.

“That’s what provides a buffer, even if you have a poor recruitment of juveniles in a given year,” Lipcius said. “As long as you have those females, you can be confident that you will have a good recruitment of juveniles the following year.”

The VMRC board was briefed on the survey results Tuesday. VMRC commissioner John Bull said the board has worked hard to improve the bay blue crab stock, especially in the last three years. Only 69 million spawning age females were recorded in 2014, the fourth lowest recorded by the survey, according to the press release.

“That was a warning siren, and the board here responded,” Bull said.

The board set a public hearing and vote on crab management measures for June while it considers options.

“They want more information to base a deeply informed management position when the public hearing of the vote comes up at the end of June,” Bull said.

Commercial harvest in the bay increased by 20 percent last year and by 71 percent since 2014, according to the press release. Crab abundance has also increased since 2014 by 53 percent.

“They’re seeing a lot of crabs out there and catching the bushel limits routinely,” he said.

Some local watermen, however, have misgivings about the survey and its implications.

Ben Johnson, of Johnson and Sons Seafood in Eclipse, said he had concerns about the merit of the study and the regulations that are based on its results.

“It’s at the point now where the regulations are tying our hands with what we can do,” Johnson said.

He said a “significant number” of small crabs have been found when they have dredged for oysters in the winter the past few years.

These juveniles were found in tributaries and shallow waters, where the blue crab winter dredge survey vessel is unable to navigate. Lipcius said more funding will be required to extend the survey into shallow waters.

“The funding has not been appropriated yet,” he said.

Johnson expressed concern as to whether these regulations and strategies are necessary or effective. Above all, he is concerned about the sweeping consequences for families trying to make a living.

“It’s a small piece of science that a lot of people’s livelihoods are based on,” he said. “A tremendous amount of people are trying to support their families and make a living.”

The Chesapeake Bay Stock Assessment Committee, a subcommittee of the Sustainable Fisheries Goal Implementation Team, will release its full analysis of the survey results in the 2017 Blue Crab Advisory Report this summer.