A whale has been spotted swimming in New York City’s East River, close to the waterfront of Manhattan’s Upper East Side.

US Coast Guard petty officer Frank Iannazzo-Simmons told the Associated Press that he and his colleagues had not seen the whale first-hand, but deduced from photos that it appeared to be a humpback.

A photo of the whale was posted on Twitter by Chief Harry J. Wedin, NYPD Chief of Special Operations Division, on Saturday.

#Harbor spotted another whale in the E. River this morning right next to Gracie Mansion. Even the wildlife want to ring in #NYE2017 in #NYC pic.twitter.com/oQNbnGBirm — NYPD Special Ops (@NYPDSpecialops) 31 December 2016

Iannazzo-Simmons called for crews of the city’s ferries, tourist boats and private vessels to exercise caution for the sake of the animal, and to “let the whale be the whale.”

Whale sightings are becoming increasingly common in New York City, with 20 individual whales spotted in 2016 alone. According to Gotham Whale, a New York-based marine tracking group, 50 whales have been spotted in the city since 2011.

North Atlantic Humpbacks breed in Caribbean waters, but travel north to the colder, fish-rich waters of the Arctic. Fully-grown humpbacks can measure up to 16 metres in length, and weigh up to 30,000kg.

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Paul Sieswerda, executive director of Gotham Whale, told the Guardian: “It’s uncommon for whales to be around this late in the season, and even more unusual for them to be in the harbor. Humpbacks would normally be heading for the warm waters of the Dominican Republic.”

However, the whales are not necessarity disorientated. Their presence has been attributed to the increase in the local population of menhaden – a type of Atlantic fish favoured by whales – thanks to clean-up projects and fishing caps in and around New York State.

An NYPD Harbor Unit boat follows a whale heading south on the Hudson Credit: getty

“We know that the menhaden population has increased and we think that’s because [fishermen’s] total allowable catch has been restricted,” said Sieswerda. “We’re working hard to convince the authorities to maintain that limit.”

In November 2016, a young humpback whale was sighted of the coast of NYC’s Long Island, stranded on a sandbar in Moriches Bay. Despite efforts by the US National Oceanic Atmospheric Administration (NOAA) to save the whale, it had “neurological abnormalities, and extensive skin injuries with evidence of infection” – and was later euthanised.

However, not every NYC whale sighting ends in tragedy. Also in November, a humpback was spotted in the Hudson River – and Sieswerda said it later returned to open water.

“We followed that whale for a number of days,” Sieswerda told the Guardian. “It was last seen in early December in the ocean. We’re quite sure that it was lunge-feeding on the menhaden.”