Boaters on Long Island Sound are being warned to watch out for whales.

Over the past several days, boaters off the Connecticut coast have spotted humpback whales, and the National Oceanic and Atmospheric Administration on Tuesday urged caution, noting that the whales appear to be feeding.

NOAA, along with officials from the Riverhead Foundation for Marine Life and Preservation and Connecticut’s Mystic Aquarium, are asking boaters to watch out for the hulking visitors and observe safe viewing guidelines.

Members of the public should stay at least 100 feet away from the whales, which can grow up to 60 feet long and weigh 40 tons. Humpbacks are endangered and protected under the Marine Mammal Protection Act, which makes harming, injuring, killing, chasing or harassing marine animals punishable by up to a year in prison or fines of $20,000.

Whales can be seriously injured or killed if struck by a boat, and boats can suffer significant damage that could leave fishermen stranded.

Boaters should watch for patches of bubbly, cloudy water, which is a sign a whale is feeding. Whales create the bubbles to confuse and trap their prey, NOAA said.

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Riverhead Foundation spokeswoman Rachel Bosworth said boaters can report sightings and whale injuries in New York waters to the foundation’s 24-hour stranding hotline at 631-369-9829.

Other options to report sightings include NOAA Fisheries’ Marine Mammal Stranding and Entanglement Hotline at 866-755-NOAA (6622).