Up to 10,000 adult moss bunker fish died Thursday in Centerport Harbor after they became trapped and oxygen levels in the water dropped, Huntington Town officials said.

The dead fish were found on the north side of the Mill Dam Bridge in Centerport Harbor. Town officials said they received about 15 calls from concerned residents.

“It appears they died in a small pocket along the shoreline last night because of lack of oxygen,” town spokesman A.J. Carter said Thursday. “Once again too many fish in a small area; there were an abundance of bunker and a shortage of predators.”

The same type of fish kill occurred late last month when an estimated 11,000 juvenile and adult bunker fish became trapped as the tide went out. That incident was the largest fish kill seen in the town since a mass die-off in Cold Spring Harbor 30 years ago, town officials said.

Carter said officials plan to keep the tidal gates open between Mill Pond and Centerport Harbor.

“Let the tides flush the fish further out into the Sound where they will eventually sink,” Carter said. “It’s not a water quality issue.”

On Monday evening south of the bridge, 300 to 500 dead adult bunker fish were found in the Mill Pond. Those fish likely suffocated because of storm water runoff from heavy rains that day, officials said. Such runoff water contains very low dissolved oxygen.

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Such events tend to happen in warmer months when oxygen levels are low and the energy used by fish increases, state Department of Environmental Conservation officials said last month.

Carter said that if the fish don’t wash out into the Sound, town officials may clean the shoreline of Centerport and Fleets Cove beaches.