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Heat Wave Blamed For Massive Oyster, Fish Kill In Mamaroneck Harbor

This story has been updated.

Numerous dead oyster shells and dead fish were found along Harbor Island Park's public beach on Tuesday evening. They washed up from Mamaroneck Harbor which connects with Long Island Sound.

Numerous dead oyster shells and dead fish were found along Harbor Island Park's public beach on Tuesday evening. They washed up from Mamaroneck Harbor which connects with Long Island Sound.

Photo Credit: Megan McCarthy
A close-up of one of hundreds of dead fish at Harbor Island Park's beachfront along Mamaroneck Harbor on Tuesday evening.

A close-up of one of hundreds of dead fish at Harbor Island Park's beachfront along Mamaroneck Harbor on Tuesday evening.

Photo Credit: Megan McCarthy
Mamaroneck Harbor as it looked from a distance in the Village of Mamaroneck on Tuesday evening.This view is from the filtered/netted swim area, so no dead fish are there.

Mamaroneck Harbor as it looked from a distance in the Village of Mamaroneck on Tuesday evening.This view is from the filtered/netted swim area, so no dead fish are there.

Photo Credit: Megan McCarthy
Another close-up at Harbor Island Park's beachfront near Mamaroneck Harbor on Tuesday evening.

Another close-up at Harbor Island Park's beachfront near Mamaroneck Harbor on Tuesday evening.

Photo Credit: Megan McCarthy
Another view at Harbor Island Park's beachfront near Mamaroneck Harbor on Tuesday evening.

Another view at Harbor Island Park's beachfront near Mamaroneck Harbor on Tuesday evening.

Photo Credit: Megan McCarthy
Photo from happier times. Monday, Mamaroneck residents called village officials about a major fish kill at Harbor Island Park. State Department of Environmental Conservation officials confirmed reports of fish kills possibly due to warm harbor water.

Photo from happier times. Monday, Mamaroneck residents called village officials about a major fish kill at Harbor Island Park. State Department of Environmental Conservation officials confirmed reports of fish kills possibly due to warm harbor water.

Photo Credit: File photo

MAMARONECK, N.Y. -- State environmental officials say this summer's excessive hot temperatures, and extended heat waves -- which caused a major local algae bloom -- are the likely source of a massive fish kill in Mamaroneck Harbor and other New York waterways.

On Tuesday, the remains of dead oysters and other seafood were washing up on a public beach at Harbor Island Park.

Village of Mamaroneck officials reported on Monday that they'd received numerous complaints about dead fish floating near Harbor Island Park -- in Mamaroneck Harbor and elsewhere in Long Island Sound. State and local officials agreed that a sudden, steady change in oxygen in the water may be killing fish.

Wendy A. Rosenbach, a regional spokeswoman with the state Department of Environmental Conservation in New Paltz, N.Y., said an exact cause is unknown, but confirmed that the fish kill reports in Mamaroneck are consistent with others being reported from other New York and New Jersey waterways. 

Rosenbach told Daily Voice: "DEC was recently made aware of a fish kill in Mamaroneck Harbor. The exact cause or extent of the of the fish kill is unknown, but fish kills tend to occur in warmer months when the water’s capacity for dissolved oxygen is reduced and fish metabolic rates increase."

"In these conditions, fish caught in these low dissolved oxygen areas can asphyxiate and a fish kill results," Rosenbach said. "In recent weeks a number of fish kills of Menhaden have been reported in Long Island and New Jersey."

On Tuesday evening, Megan McCarthy, a Daily Voice community advisor and local Coldwell Banker agent, shot beachfront photographs of the devastation. While the massive fish kill and dead oyster remains were not visible from Route 1 (Boston Post Road) in the Village of Mamaroneck, they very real at the water's edge at Harbor Island Park.

On Monday, village officials sent an email blast to local residents and business owners, that said read: "The Village of Mamaroneck has received a number of inquiries about fish-kills, or fish die-offs in Mamaroneck Harbor."

"Fish kills generally occur in warmer weather, when algae growth increases, then dies off and is consumed by decomposing organisms, which give off waste by-products, subsequently lowering the oxygen levels in the water that fish need to breathe," Mamaroneck officials said in their email.

"Natural conditions often are a factor in fish kills, such as extreme temperatures or sudden temperature changes, diseases or parasites, naturally occurring low oxygen levels, or algae blooms," the village email continued. "The most likely anthropogenic cause is a drastic drop in dissolved oxygen in the water in association with an algae bloom triggered by fertilizer, wastewater, and/or stormwater flowing into the harbor from upstream."

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