With strong indications that the Bay’s blue crab population is at a low level, scientists from both Virginia and Maryland say the catch must be reduced to protect both the health of the stock and, ultimately, the income of watermen.

A 27-member work group of scientists and economists was planning to deliver that message to the Bi-State Blue Crab Advisory Committee at a late-September meeting.

If it agrees with the scientists, the Bi-State Committee — made up of lawmakers, state officials, watermen, environmentalists and others — may recommend actions to reduce blue crab harvest pressure.

If so, that would spur a series of “listening sessions” this fall to get input from watermen and others before any actual regulations are put forth, said Ann Swanson, executive director of the Chesapeake Bay Commission, which coordinates the Bi-State Blue Crab Advisory Committee and its scientific work group. Recommendations for specific regulations for managing the Bay’s most valuable commercial fishery could emerge by the end of the year.

For years, the lack of data — or the presence of seemingly conflicting data — made management decisions difficult, even as some scientists expressed growing concern about the health of the blue crab population.

Maryland recently reported that its catch from April to July, the first four months of this year’s season, was 9.7 million pounds, the lowest ever reported for that period. It was about a third lower than average.

With the “statement of consensus” — reached after nearly two years of meetings — Swanson said Bay scientists for the first time are “all singing from the same sheet.”

In their consensus, the scientists agreed that the Baywide abundance of all ages of crabs is down, the mortality rate from fishing is increasing, and the spawning stock biomass — a measure of the population’s ability to reproduce — is below the long-term average.

At the same time, the panel said, more effort is being aimed at the crab. The result is that most crabs are harvested as soon as they molt to the legal 5-inch catch size. Few are left to grow larger — and more valuable.

Still, the scientists warned there is potential for fishing pressure to increase in the Bay. Both Maryland and Virginia have put caps on the number of commercial fishermen, and the amount of equipment they can use, but those caps have not yet been reached.

In Maryland, for example, only about 17 percent of the crab pots licensed are actually being fished, according to a recent report prepared for the bi-state committee.

Also, there is no limit on the number of people who can catch crabs recreationally, the scientists noted.

The result, according to the scientists, is bad news for both the crab and for fishermen. Watermen are using more equipment and spending more effort to catch fewer crabs, and the crabs are smaller and less valuable. For example, in the 1970s, 100 crabs yielded 13 to 14 pounds of crab meat; the same number today yields only 7 to 10 pounds, according to a report for the Bi-State committee.

That’s also bad for the crabs because large crabs have greater reproductive potential than small crabs.

Earlier this year, a separate group, the Chesapeake Bay Stock Assessment Committee, also warned that the blue crab stock was “fully exploited” and that the current catch rates left little margin for safety.

But figuring out exactly what the right harvest target should be is a difficult job. This summer, the Bi-State panel brought scientists from the Bay region and elsewhere along the East Coast together for a three-day session to review data and discuss harvest limits. Their recommendations could include catch limits aimed not only at protecting the stock, but at improving the fishery as well.

For example, a catch threshold intended to protect the stock from overfishing could be different from a harvest target aimed at allowing crabs to grow larger. Bigger crabs would be more valuable, potentially allowing watermen to earn more money by catching fewer — and with less effort.

If the bi-state committee accepts any recommended harvest limit, it would be presented to the public in a series of community meetings before regulations are proposed to implement them, Swanson said.

One possible regulatory change that has been suggested is the creation of a “rights-based” fishery. In such a system, watermen would be assigned rights to catch a certain number, or weight of crabs, or to a certain amount of fishing gear.

Such caps could reduce pressure on watermen to harvest greater numbers of small crabs before someone else catches them. Watermen expressed some reservations about such a system during a stakeholder meeting conducted by the bi-state panel earlier this year.

Besides actions aimed at the fishery, the 27-member scientific workgroup emphasized the need for the further protection of underwater grass beds, which serve as important nursery areas for juvenile blue crabs.

The group also endorsed the establishment of migratory corridor sanctuaries aimed at protecting female crabs as they migrate down the Bay to spawn. Earlier this year, the Virginia Marine Resources Commission created a 660-square-mile sanctuary in waters more than 35 feet deep to allow for the safe passage of migrating female crabs.

In addition, the scientists said the Bay states need to develop a marketing strategy touting the benefits of Chesapeake Bay crabs, which have faced growing competition from foreign crab meat imported in recent years.