Federal officials in June gave the go-ahead for the largest aquaculture experiment yet conducted with sterile nonnative oysters in the Bay.

The Army Corps of Engineers issued a permit June 23 allowing the Virginia Seafood Council to distribute 1.3 million oysters among 13 growers around Virginia’s portion of the Bay after the U.S. Fish and Wildlife Service dropped its objections to the project.

It is the latest in a series of projects by the council exploring the aquaculture potential for sterile Crassostrea ariakensis. A main goal of this year’s project was to determine whether oysters placed in the water in late spring or early summer would reach market size by fall.

The project had been planned to begin in early June, but the U.S. Fish and Wildlife Service asked the Corps to delay the permit, saying the project’s risks outweighed its benefits and suggested that further aquaculture projects be postponed until an environmental impact statement examining nonnative oyster use is completed.

Although the oysters are grown in cages or bags, the service warned that increasingly large projects also increase the potential for oysters to be lost during handling, which has happened in the past.

Although the risk of reproduction is low, it is still a possibility, the service noted. The oysters, produced by the Virginia Institute of Marine Science, were reared using a technique that is 99.9 percent effective in rendering them sterile, meaning 1 in 1,000 may be able to reproduce.

The service also said the continued reuse of the same sites increases the chance of reproduction and therefore an introduction of the species into the Bay.

But after a delay, the service decided not to ask for a higher level review of the issue by the Corps, the agency responsible for issuing a permit for the project.

The proposal originally had called for distributing 1.5 million oysters among 15 growers, but two participants dropped out of the project.

The seafood council has been conducting increasingly large in-water experiments since 2001, with results suggesting that aquaculture can be a profitable venture for participants. The council reported last year that in a past experiment, growers who were given 100,000 oysters apiece made investments of between $3,000 and $7,500 and had returns of $5,000 to $22,000.

Delays in hatchery production have resulted in past projects not beginning until late summer or early fall, and the council is interested in learning whether an earlier start would produce marketable oysters faster, especially in low-salinity areas where they grow more slowly.

The largest previous deployment was 1 million oysters in a project that began last year and ended in June.