STONINGTON (AP) – A lobster hatchery has begun the process of raising more juvenile lobsters to be released into the wild after thousands of the hatchery-raised lobsters died this week when an air pump malfunctioned.

An estimated 12,000 or so tiny lobsters were discovered dead in their tanks on Wednesday, a day before they were set to be released into selected waters along the Down East coast as part of a pilot lobster seeding project.

The loss of the first batch of lobsters is a setback, but plans are under way to raise more juvenile lobsters, said Robin Alden, executive director of Penobscot East Resource Center, which is running the lobster hatchery in partnership with local lobstermen.

Problems are to be expected in running a hatchery, Alden said. The juvenile lobsters, which were just under an inch long, died after air failed to be pumped into the their tanks.

“This is research; this is not making cookies,” she said. “It’s unrealistic to do something like this and to expect that everything is going to go right all the time.”

The project is aiming to raise lobsters until they are roughly 12 to 15 days old and reach a size known as Stage 4. At that age, they would be released in selected sites in the state’s lobster Zone C, which stretches from Cape Rosier in Brooksville to Jericho Bay and out to Matinicus Island.

A hatchery committee has been working with 900 lobster fishermen in the zone to identify which sites should be stocked. When lobsters reach Stage 4, they are ready to move from near the surface of the ocean, where they are easy prey for their predators, to the bottom, where they can find shelter and food.

Aeration is a key element in the lobster-rearing process at the hatchery, which raises young lobsters from eggs inside 100-gallon conical tanks with air pumped into them. The tanks failed to get enough air blown into them, Alden said.

She said 7,000 to 8,000 juvenile lobsters were released into the ocean last week, and that the tanks held an estimated 12,000 more that were scheduled to be released on Thursday.