Scientists in Virginia and Maryland are planning an experimental release of 40,000 hatchery-raised crabs to boost the Chesapeake’s dwindling crab population.

The crabs will be placed in selected tributaries this summer to see if rivers and creeks that don’t seem to have many crabs will be able to support them. If the crabs thrive, the experiment could be the first step toward supplementing the Bay’s dwindling crab population through captive breeding.

“We’re just starting to explore a new avenue,” said Yonathan Zohar, director of the University of Maryland Biotechnology Institute’s Baltimore lab. “I can’t say whether this is going to be commercially successful or not, but I think this is a tool we cannot afford to ignore.”

Blue crab harvests have dropped from 55 million pounds in 1993 to a low of 20.2 million pounds in 2000. Maryland and Virginia officials are imposing new restrictions on crabbers to help the crab population recover.

Researchers have discovered that lengthening spring and summer days will prompt crabs to become fertile and mate. By exposing the crabs to long, artificially balmy and bright days, scientists have triggered year-round mating and hatching.

The process to raise crabs from eggs to adulthood in a hatchery takes eight months in the lab, although experts think that in the wild, most crabs take two years to mature.

Biologist Rom Lipcius of the Virginia Institute of Marine Science would like to use hatchery crabs to test a theory that some of the Bay’s rivers and creeks could support more crabs than they do.

In experiments on the York River, Lipcius found that young crabs rely on tides to carry them upstream into rivers and creeks, and they aren’t spread out evenly. Another experiment found that while crabs were most abundant in underwater grass beds that are considered prime nursery areas, a greater percentage of crabs survive to adulthood in muddy or sandy areas upstream. “That’s been a real surprise,” he said. The crabs may be thriving in muddy areas because they have fewer predators and more of the clams that are their favorite food, he said.

Lipcius wants to plant hatchery crabs in grassy areas and others on muddy bottoms and see where they end up. The results could show whether some areas that produce very few crabs now might yield more with hatchery-raised animals, he said.

Lipcius intends to conduct the experiments this summer if the hatchery can produce enough baby crabs. If not, he’ll do a trial run with crabs caught elsewhere in the Bay and moved to the experimental areas.

The proposed experiment would need approval from fishery managers in Virginia and Maryland.