NEW YORK — When Dr Rachel Dubroff and her family chose their apartment at Riverside Boulevard and 63rd Street in Manhattan, they were thrilled by its picturesque views of the Hudson River. But they did not expect to have a front-row seat to an annual whale-watching event.

For two years in a row, Dr Dubroff said on Tuesday (Nov 22), she has spotted a whale swimming outside her living room window. Last year, she didn’t quite believe the sighting was real. But she saw a whale again on Saturday — and in the same spot again on Sunday — and news reports confirmed her hunch: The Hudson River has a resident humpback.

“It was general excitement and shock,” Dr Dubroff, 39, said, “and how thrilling that a whale can be in the Hudson, based on what we see float by sometimes.”

Indeed, the Hudson, as scenic as it is, does not scream “whale habitat”. But experts say cleanup and conservation efforts have led to cleaner waters and an abundance of fish, amenities that have attracted at least one humpback whale to the river waters off Manhattan this month.

There are other humpbacks in waters nearby. The Coast Guard said in a statement on Monday that it had fielded reports of a second whale sighting in northern New Jersey waters, swimming from Sandy Hook to Raritan Bay. And according to Ms Jen Goebel, a spokeswoman for the National Oceanic and Atmospheric Administration, humpbacks have been spotted near New York.

The city-dwelling whale that Dr Dubroff saw last weekend is thought to be the same one that has traversed the waterway, travelling to Liberty Island and to the George Washington Bridge, since it was first sighted around Nov 9, according to the Coast Guard.

Mr Paul Sieswerda, the president of Gotham Whale, an organisation that tracks marine life around the city, said the whale had been seen by New Yorkers who have captured photos and videos of it feeding and swimming.

Mr Sieswerda said that it was common to see humpbacks in the waters off New York at this time of year, as the whales finish up their feeding season and begin to think about heading south to breed in warmer waters.

“The whales found this spot as a feeding ground,” he said. “Rather than go all the way up to Massachusetts and Maine, they’ve found a good feeding ground right here in New York.”

The Hudson whale, which Mr Sieswerda nicknamed Gotham, seems to be healthy and has been exhibiting a behaviour called lunge feeding, in which a whale swims forward, mouth agape, as it captures thousands of gallons of water.

Inside the gulps, Mr Sieswerda said, are likely sizable amounts of menhaden, a small forager fish that fishermen call bunker — a veritable fish buffet.

A whale appearing in the Hudson is very rare, Mr Sieswerda said, which is why he thinks this one is a solo traveler. But the whale still faces significant danger because it is swimming in traffic-laden waters.

“It’s in a very busy area of high-vessel activity, and it’s going up and down the Hudson, inside the harbour where big ships are,” Mr Sieswerda said. “So far, it seems to be OK and, hopefully, can detect the boats.”

The Coast Guard has urged boaters and fishermen to slow down to avoid distressing the humpbacks, which can grow to 18m and can weigh around 36,300kg.

“When you have whales chasing the bunker, and fishermen chasing the stripers that chase the bunker, accidental interactions between whales and vessels can occur,” Mr Jeff Ray, a deputy special agent with NOAA’s law enforcement division, said in the Coast Guard’s release.

Kayakers and boaters should take extra care to steer at least 30m clear of any whales in the area, according to Ms Goebel, the NOAA spokeswoman.

Elsewhere, trouble can lurk for whales in shallow waters. About 128km from Manhattan, a humpback whale spent a week stuck in Moriches Bay, off the southern coast of Long Island.

On Tuesday, the juvenile whale remained trapped on a sandbar, unable to free itself in 1.2m of water for two days.

The whale was lured here about a week ago by the promise of fish and the strong tides of the supermoon, but hope for its escape is fading fast. Ms Goebel said that the outlook for the whale was not good, and that the animal might require euthanasia in the coming days.

Mr Chuck Bowman, the president of the Riverhead Foundation, which studies marine life, said on Tuesday that the group was awaiting guidance from NOAA.

“The good thing was 30 years ago you’d see maybe one whale off of Long Island a season,” Mr Bowman said. “Now you see them all the time due to conservation efforts.”

But, he added, “You get a bigger population and you get a greater chance of things like this happening.” THE NEW YORK TIMES