Vineyard ponds may be in peril, but somebody forgot to tell that to the Tisbury Great Pond which is loaded with wild oysters this year, the biggest natural spawning of oysters in recent memory.

“It is huge,” said Rick Karney, who has been director of the Martha’s Vineyard Shellfish Group for over 30 years. “I’ve never seen anything like it,” Mr. Karney said.

The pond is teeming with baby oysters — rocks and shells in the pond are coated with them. The juvenile oysters are about an eighth of an inch in size; by next week, many will have doubled in size.

Mr. Karney won’t put a number on it. “I’d say too numerous to count,” he said, standing in Chilmark shellfish constable Isaiah Scheffer’s skiff on Wednesday during a one-hour tour of the pond.

“It is biblical,” Mr. Karney declared. It was his first look at the oyster hatch this summer, which has found him mostly in the Lagoon Pond hatchery tending the juvenile shellfish he is raising there.

Mr. Karney estimates that sometime between June 12 and July 4 there were probably several wild oyster spawnings, perhaps encouraged by a combination of warm weather, a healthy, salty water column and a steady rejuvenation program by town shellfish departments. One female oyster is capable of producing 15 million spat. Over several days, the pond waters were filled with floating microscopic oyster larvae. They drifted and swam across the pond, settling on the bottom like so much falling snow.

At the Martha’s Vineyard Land Bank’s Sepiessa Point, evidence of the oyster spawn is all along the shoreline. Tiny shellfish cling to rocks of every description, broken shells and even seaweed.

Mr. Scheffer, 34, said he first noticed it on Wednesday, July 21. “I said to myself, wait a second. I called Rick,” Mr. Scheffer said. “I called everybody. It is unbelievable. This is a once-in-a-lifetime event.” He took a picture of tiny oysters that had taken up residence on sea lettuce.

Reportedly the Edgartown Great Pond is having a banner year too for wild oysters, although not as large as in the Tisbury Great Pond.

It takes three years for an oyster to reach harvestable size. Even if only half of one per cent of these oysters make it to adulthood, the bounty will be significant. “The fishermen may be able to fish on this for 10 years,” Mr. Karney said.

More than 10 years ago the oyster populations in both great ponds were decimated by Dermo, a southern water shellfish disease that is not harmful to humans but ruinous to oysters. The disease began infecting Edgartown Great Pond in 1996 and Tisbury Great Pond in 1999. It led to the collapse of the oyster fishery.

And now Island shellfish biologists are happily bearing witness to a turnaround.

“They are growing at a fast rate right now,” Mr. Karney said. He wondered aloud at how much the water clarity in the pond will improve with so many thousands of filter feeders now present.

Among other things, oysters are known for their cleansing ability because they feed on plankton. A single adult oyster can clean two gallons of water in an hour.

Earlier this week, the Tisbury Great Pond was reopened to the sea and the water level in the pond dropped several feet, stranding thousands of juvenile oysters in the open air along the shoreline. Both Mr. Scheffer and Mr. Karney spent some time on Wednesday afternoon picking up pieces of shell coated with oysters and pitching them back into the pond. The oysters will die if they are not returned to the water.

The two men said they will appeal to the community for volunteers to walk the shoreline and help throw the oysters back in the pond.

A robust oyster population in the long term will jump start the blue crab fishery too, since blue crabs are oyster predators.

The oyster population boom comes amid concerted efforts by shellfish biologists across the Island to maintain, boost and restore shellfish populations in saltwater ponds.

The great ponds pose unique challenges because they are not naturally open to the sea; rather the ponds are opened by mechanical means several times a year through the use of a bulldozerr that cuts a path through the barrier beach. This helps to keep the ponds clean and infused with fresh saltwater; left to their own devices the ponds would return to a more fresh water state, except when they are opened to the sea in severe storms.

Over the years the shellfish group has been raising baby oysters in its hatchery and sowing them by the millions into the great ponds. Biologists have successfully experimented with genetic tagging to raise oysters that are resistant to Dermo.

Oyster restoration projects have included spreading broken shells on the bottom of the ponds to create culch, a layer of material that oysters cling to and grow on, above the mud and sand on the pond bottom.

Mr. Scheffer has worked for four years as the Chilmark shellfish constable, and has been deeply involved in shellfish propagation and restoration.

On the West Tisbury side of the pond, Jeff Lynch was recently appointed shellfish constable following the death of longtime constable Tom Osmers. Mr. Lynch has worked for Mr. Scheffer as an assistant constable.

Mr. Scheffer said the Edey Foundation and the Menemsha Fisheries Development Fund have provided funding to help establish remote sets of oysters in the pond.

“Over the last two years there have been efforts to restore the populations in Tisbury Great Pond. To what extent these efforts have played in this summer spawning, it is difficult to say,” Mr. Karney said.

Meanwhile, Edgartown shellfish constable Paul Bagnall confirmed that this is a good year for oysters in the Edgartown Great Pond. Mr. Bagnall credits the efforts of William (Boo) Bassett, who has worked under a grant from the Great Pond Foundation and the Jewish Community Foundation to restore oysters in the pond.

“It just goes to show that municipal propagation works well, especially when Mother Nature kicks in. And she can really kick in. This will be good for the fishermen. This will be good for the blue crabs and it will be good for the pond,” Mr. Bagnall said.