A blue crab conservation strategy instituted by Maryland, Virginia and the Potomac River Fisheries Commission in 2008 seems to be working, according to a federal study that recommends that restrictions on harvesting breeding-age females remain in place.

If the restrictions aren’t lifted, the crab harvest will rise by 200 million crabs in about five years, about a 50 percent increase from the current harvest of about 400 million, said Thomas Miller, the study’s lead author.

The fisheries commission was created by Maryland and Virginia in 1958 to manage the joint fishery.

The restrictions on taking females have already had great success in raising the number of breeding females in the Chesapeake Bay, which are integral to raising abundance as a whole, according to the study, which was released in August.

The study’s conclusion “represents the best available science on the stock’s reproductive capabilities, lifespan, gender and size distributions” and supports continuing to preserve female crabs, Maryland Department of Natural Resources officials wrote in an Aug. 9 statement that followed the study’s release. “These more stringent assessments of the stock’s health will allow fishery managers to set more precise female harvest limits in order to fully rebuild the stock.

In 2007, the year before the new rules were put in place, the baywide harvest of crabs fell to 44.5 million pounds, the lowest since at least 1959, according to the report. By 2009, the most recent figure available, the harvest had crept back up to 53.9 million pounds.

Ideally, the bay will come to harbor about 415 million crabs that are a year old or older, the study states, with 215 million of those being female, the level observed in the mid-1980s, when abundance is thought to have most recently peaked. These levels would represent a sustainable abundance plus a buffer for safety, Miller said. Currently the bay contains about 160 million adult females at least a year old.

Miller is head of the Chesapeake Biological Laboratory on Solomons Island, a scientific facility studying waterways and the environment that is run by the University of Maryland’s Center for Environmental Science. He and his co-authors conducted the study for the National Oceanic and Atmospheric Administration, a federal agency that monitors the oceans and weather.

It’s difficult for officials to know exactly what factors are behind the crab population’s crash and nascent recovery, Miller said, though overfishing probably played a role in the decline. It’s also uncertain what the crabs’ rebound heralds for the health of the ecosystem as a whole.

While the study recommends keeping the restrictions, the scientists’ ultimate role is to tell policymakers what is physically possible, not what they should do, Miller said.

“We can tell managers and stakeholders what they can’t have, the limits to sustainability,” Miller said. “We can suggest things like a target, we can suggest things like what they might choose to aim for, but that may not be what society wants.”

Watermen’s opinions are divided as to what should happen next.

Larry Simns, president of the Maryland Watermen’s Association, opposed the restrictions initially, but the results have changed his mind, he said. Regulation deserves some, though not all, of the credit for the rebound.

“Protection of the female crabs had an input on it, but also we had a phenomenally great patch for crabs,” Simns said. “It wasn’t all what man did. Mother Nature did most of it because we had crabs in North Carolina, South Carolina, up in New Jersey and New York and places where they haven’t had them. Evidently the conditions were right for a great spawn.”

Still, “you should always protect female breeding stock,” he said, and the rules should remain in force. Watermen should “make a sacrifice for a couple years and then reap the harvest a couple years later.”

However, Tommy Zinn, president of the Calvert County Watermen’s Association, said the rebound means that watermen should be allowed to harvest more females again. Watermen don’t target females anyway because they are smaller and fetch lower prices than do males, he said.

“It isn’t that they’re going to be overfished or fished to extinction,” Zinn said. “There’s quite a few safety valves in place.”

One of the safety measures is a ban on winter commercial dredging, or scraping the bay bottom, which has been in place in Maryland for years but recently was enacted in Virginia. Winter dredges in the southern end of the bay tended to net females because they spend the winter nearer to the bay’s mouth than do males, Zinn said.

Bobby Abner, a waterman and owner of the Abner’s Crab House restaurant in Chesapeake Beach, lauded the state for imposing the rules but believes that officials now should lift them.

“I thought it was a waste of time [at first], but I feel like I was wrong,” he said. “Because now we got them stronger than we ever had them. Now it’s a healthy industry. . . . I’m not saying we won’t need more regulations down the road, but right now, I think we’re all right. But what they did back three years ago was the right thing to do at the right time, and the government did the good thing.”