Large numbers of humpback whales have returned to NYC for the first time in a century

A humpback whale spyhops off Rockaway Peninsula with the Empire State Building in the background September 23, 2013 in the Rockaway Beach neighborhood of the Queens borough of New York City. A humpback whale spyhops off Rockaway Peninsula with the Empire State Building in the background September 23, 2013 in the Rockaway Beach neighborhood of the Queens borough of New York City. Photo: Artie Raslich/Getty Images Photo: Artie Raslich/Getty Images Image 1 of / 9 Caption Close Large numbers of humpback whales have returned to NYC for the first time in a century 1 / 9 Back to Gallery

The sight of a humpback whale fluke set against the New York City skyline is an anomaly no longer.

For the first time in 100 years, sizable numbers of humpback whales are being spotted in the waters off NYC, and it's thanks to years of environmental clean-up efforts, Popular Science reports.

"Because of the improvement of the water quality, algae and zooplankton have multiplied, giving good food for the menhaden [a small fish eaten by whales], which have returned in numbers that the fishermen say they have not seen in their lifetimes," Gotham Whales founder Paul L. Sieswerda told Pop Sci.

Until the enactment of the Clean Water Act in 1977, New York City's waters were a dumping ground for everything from medical waste to factory run-off. Some of those chemicals were cancer-causing, the EPA said.

New Yorkers have seen a significant rise in whale sightings over the past few years, and the trend is only accelerating in 2017. The whales are thought to be ducking into New York for a bit of sightseeing and feeding on their migration routes up and down the coast. Back in November, a whale was seen near the Statue of Liberty, prompting the Coast Guard to send out warnings to nearby boaters.

The whale sightings are so frequent, there are multiple ferry companies offering whale-watching tours.

On a recent American Princess Cruises excursion, lucky whale-watchers saw four humpbacks in a single trip. In 2016, the Telegraph reported that 20 whales were seen all year.

A similar trend, also credited to conservation efforts, has been seen with the shark population in California. The Clean Water Act and the Marine Life Protection Act have boosted the numbers of great white sharks — and marine mammals in general — according to scientists.