The Harbormaster Department is now serving as nanny to 250,000 baby oysters, tucked into a watery bivalve nursery in Onset called an "upweller."

Dredging, overfishing, and a disease that is particularly harmful to oysters, called "Dermo," have all transformed Onset Bay from a place once overflowing with oysters, to a place where oysters now struggle.

The Harbormaster Department is hoping that growing its own oysters and, when they're large enough, moving them into the bay will help revive the population.

The upweller looks like just another wooden dock floating adjacent to the Onset Pier, but beneath trap doors are eight troughs containing 250,000 oysters, currently approximately 2 millimeters in size. The oysters will grow in the troughs while nutrient rich water is pumped in and out by an electrical engine.

"They won't go out until next year," said Harbormaster Garry Buckminster. "They'll be here for a month or so, then we'll put them in floating cages," which are likely to be in the Broad Cove area.

Once the oysters are large enough to be in open water, they will be distributed in the area of Onset Island.

Ben Suddard, whose family has operated a "shellfish grant" and farmed oysters since the early 1900s, knows a thing or two about upwellers. He was on-hand while the Harbormaster Department set up its operation on Friday, June 14. He advised Buckminster and his crew about some of the finer points of maintaining the upweller.

"Other than very small variations, it's the same system they're using here," Suddard said of his upweller.

While the oysters in the upwellers can have a mortality rate as high as 50%, Suddard said he think the oysters will do well so long as the upweller is maintained. In the long run, he says, it will be good for Onset Bay.

"From an environmental standpoint," said Suddard, "you really can't do anything better for the health of the bay than to repopulate the oysters."

According to Buckminster, the Harbormaster Department used to set up an upweller every year, but hasn't done so in recent years.

"It's probably been stopped for four years," said Buckminster. "It's definitely a good thing to start up again."

In response to the depleted stock, the Harbormaster Department last December shut down commercial oystering. Recreational oystering followed soon after.

The project is being funded in part by an $8,000 grant from the A.D. Makepeace Company's Neighborhood Fund.