New York City’s urban waterways are again becoming home to some residents who haven’t been seen for hundreds of years: Humpback whales. A common presence in pre-colonial times, humpbacks vanished from New York’s waters as their numbers plummeted globally. But there are signs of a resurgence. In the busy New York Bay, where the Hudson River meets the Atlantic Ocean, whale spotters have recorded twice as many whales this summer as last summer, and almost 20 times as many as in 2011. Researchers say that a cleaner bay and a growing population of fish for whales to feed on are responsible for the trend.

Rise in Sightings

Four years ago, humpback whale sightings in the NYC bay area would have been rare, says Paul Sieswerda, a naturalist and founder of Gotham Whale, a nonprofit dedicated to studying whales in NYC. After spending nearly four decades working at the New England and New York Aquariums, Sieswerda retired to start Gotham Whale in 2006. In 2011 Sieswerda began to notice the increased prevalence of humpback whales in the bay. He decided to start partnering with American Princess Cruises to study whale numbers using a citizen science approach. Everyday people joined experienced naturalists on cruises to collect data. Every summer since, Gotham Whale has sponsored thrice-weekly whale-counting trips through the bay and a few miles out into the ocean. That counting has just wrapped up for the 2014 season — the whales have begun their migration south. The results are stunning. In 2011, there were 5 whales sighted over the course of the season. (Some of these were probably the same whales seen on multiple occasions.) That number increased to 25 whales in 2012, 43 whales in 2013, and for 2014, 100 whales. Citizen scientists also record the whales’ fluke markings to tell individuals apart, and the number of unique whales has increased from year to year as well, says Sieswerda.

Healthier Waters

“From common sense and a citizen science perspective, the trend in [whale numbers] is absolutely clear: it’s obvious that there are more and more whales in the NYC bay,” says Sieswerda. Two main factors seem to be driving that trend. First, the water conditions in the NYC bay area are improving due to efforts to clean up the waterway in recent years. Thanks to a $10 billion cash infusion, the water is the cleanest it has been in over a decade, according to NYC’s “State of the Harbor” 2012 report. Secondly, there’s a lot more food for humpback whales around. Menhaden, tiny silver fish consumed by humans mostly as fish oil pills, are a primary food source for humpback whales. When the species was deemed overfished in the Chesapeake Bay in 2012, the allowed Atlantic catch was drastically cut back. Since then, researchers say, 300 million more of these fish are inhabiting the Atlantic Coast. Given the short life cycle of menhaden (approximately 5-7 years), leaving an additional 300 million to swim around could lead to an even larger increase in fish numbers in coming years, says Joseph Gordon with the nonprofit Pew Trust. That might mean more whales not just near NYC but all along the New England coast in years to come. Increased whale sightings in NYC “is exactly the signs of a healthy ecosystem we hope to see more of as a result of cleaner waters, protected ocean habitat, and, of course, more abundant forage fish as a result of reasonable catch limits,” says Gordon. So far, the whale invasion seems like only good news: There have been no reported cases of whales being beached or struck by ships. And for commercial whale-watching companies in the NYC harbor, the news is even better. Tom Paladino of American Princess Cruises says they’ve seen business rise in the past four years. Now what remains is getting the locals to notice: “The biggest issue is that 90 percent of people in New York probably do not know there are whales in the harbor,” he says.

Image by Tory Kallman / Shutterstock