Starting Oct. 1, the imaginary line dividing the Chesapeake Bay between Virginia and Maryland will be erased--at least for the more than 17,000 commercial fishermen in both states who annually reap the bay's crab harvest.

Already, watermen predict the change could hurt the Virginia crabbing industry, while officials in both states say the new rules could pose difficult enforcement problems.

"There was a stable condition in the amount of watermen in both states. This will cause an increased pressure on resources if the bay is cluttered by watermen," said Tom Demming, an assistant attorney general in Maryland, who worked with Virginia officials in the recent court case that resulted in the new rules.

Currently, Virginia grants commercial crabbers' licenses only to state residents. A court ruling earlier this year invalidated the Virginia residency requirement, however, thus forcing Virginia to open its part of the bay to any commercial crabber who pays an annual license fee, which ranges from $5 to $58.

A similar case is now before courts in Maryland, where state law also requires crabbers to be state residents. Although no decision has been reached in that case, Demming said he expects the Maryland law to be overturned too, and that the state will not oppose any ruling opening the Maryland part of the bay.

The Virginia ruling came in a suit filed last year by three Maryland watermen, Elmer W. Evans, David L. Laird and Edwin Smith III, all members of the Tangier Sound Watermen's Association. In the suit, the three men contested the Virginia residency rules after they were refused licenses to crab in the Virginia part of the bay because they lived in Maryland.

In June, a federal court in Richmond declared the Virginia residency requirement unconstitutional and ordered Virginia to open its section of the bay to crabbers from any state by Oct. 1.

Even though the ruling affects both commercial and sport crabbing, Virginia and Maryland officials expect the biggest effect will be on commercial crabbers who work near the state line.

"The effect will be more pronounced near the borders because most crabbers will not feel it is viable to travel a long distance," said James E. Douglass, commissioner of the Virginia marine resources division. "We're hoping that calmness prevails near the state line ."

But with Maryland commercial crabbers outnumbering their Virginia counterparts nearly 2 to 1 (Maryland has about 11,000 commercial crabbers, while Virginia has about 6,000), Virginia watermen naturally are concerned that they may wind up the big losers in the new open-bay policy.

"If there are more crabbers, the product will be caught up sooner," said Fred Biddlecomb, president of the Virginia Watermen's Association. "If the supply is dumped, the price paid to the watermen could go down."

Even under the open-bay policy, watermen will be required to abide by each state's laws depending on the side of the bay they are crabbing. State officials say that could create difficulties in policing the bay, particularly if there is heavy traffic in crabbing grounds between the two states.

"The regulation and enforcement of crabbing is a difficult task in terms of police activity," said Maryland assistant attorney general Demming. "Both states are already undermanned to properly police the waters. Opening the boundary to crabbing back and forth over the border compounds an already difficult situation in terms of sheer logistics of enforcing water laws."

Eventually, Maryland and Virginia officials hope to revise the crabbing laws to make the rules more uniform. But no changes will be made before Oct. 1, since neither state legislature meets until January.

"We may see a restructuring of both state's laws in the long term, but there is not enough time to implement any before Oct. 1," said Margaret Johnston, executive director of the Chesapeake Bay Commission. "We will meet Sept. 30 and Oct. 1 to draw up a set of proposals that will be sent to both state legislatures."

Some fishermen are concerned that the ruling on crab licenses could set a precedent that opens other commercial fishing to out-of-staters.

But the major concern this year is among crabbers, and some watermen believe the new rules will have little effect on this year's crabbing season.

"Next spring will tell the tale," said Virginia waterman Biddlecomb. "Crabbing is on the downswing now and around Oct. 30 productivity will be way down because they will be moving too fast to the ocean. In the spring, the crabs will be returning to the bay in full force."