Dolphins Return to New York Harbor

Experts say the waters are now cleaner than they’ve been in the last 100 years

| 22 Jul 2022 | 04:21

Dolphins have names, distinct whistles that announce their unique presence to other dolphins. They can also recognize themselves in a mirror, express empathy, work cooperatively to hunt for food, and even mourn their dead. Perhaps the most impressive dolphin behavior is the marine mammal’s ability to sleep with half of its brain, a skill many New Yorkers would undoubtedly love to learn themselves. The dolphin shuts down half of its brain along with the opposite eye while the other half of the brain stays alert to scan for predators.

While dolphins are typically thought of as the warm water-loving marine creatures of the tropics, dolphins frequent New York’s waterways starting in the late spring. Sightings often continue throughout the summer months into the fall.

New York Harbor sees several species such as Risso’s dolphins, striped dolphins, and bottlenose dolphins. Sightings of these playful and intelligent mammals are becoming increasingly common as the city’s steady efforts to reduce pollution and raise public awareness about marine life are paying off.

Healthy Waterways

New York Harbor is currently home to thriving ecosystems and a rich diversity of animal life. However, as a major metropolis, the city has historically struggled with pollution and the environmental impacts of increasing urbanization. As New York City’s population grew the condition of the surrounding waterways deteriorated. The Hudson River in particular experienced an increase in sewage which brought bacteria and toxic chemicals, killing off numerous species and their food sources.

In the 1960s, efforts began to clean up the Hudson. Since the Clean Water Act was passed in 1972, a federal law that regulates water pollution, water samples have been taken regularly to monitor water quality and the city has undertaken projects to limit pollution levels.

Improvements to wastewater treatment is a major factor in the improved water quality and the city has seen an 80% reduction in sewer overflows since the mid-1980s. Currently, New York City treats around 1.3 billion gallons of wastewater and biosolids daily from fourteen wastewater treatment plants.

Data from the environmental advocacy group Riverkeeper found 80% of water samples from the Hudson are up to the Environmental Protection Agency’s standards for safe recreation. The harbor is the cleanest it has been in the last 100 years and experts say the major Manhattan rivers are the cleanest they’ve been since the American Civil War.

Columbia University Study

A study by Columbia University and the Wildlife Conservation Society published this June in the journal Marine Ecology Progress Series confirmed the return of the aquatic mammal to New York Harbor and credited the upsurge to a bountiful supply of dolphin’s favorite dish, bunker fish also known as menhaden.

The purpose of the study was to better understand how marine mammals are navigating New York’s urbanized waterways. “By investigating how marine predators, such as bottlenose dolphins, are behaving within heavily urbanized ecosystems, we can gain insight on how these predators influence and are influenced by their environment, which can be used to guide conservation efforts, mitigation measures, and best practice recommendations,” said Sarah Trabue, Research Assistant at Wildlife Conservation Society and the study’s lead author, in a news release.

Dolphins use echolocation, locating objects by reflected sound when they hunt and feed. The researchers set up six underwater microphones to record their “feeding buzzes,” a rapid series of clicks that show where they are chowing down. The microphones were set up at different locations off the coast of Brooklyn, Queens, Staten Island, and New Jersey. The highest predatory activity was found in the Lower Bay off Staten Island near the entrance to New York Harbor.

The increase in dolphins is also connected to climate change. Warming oceans due to global heating has led marine animals to expand their territories and foraging grounds. “We’re seeing species we didn’t see as frequently getting themselves into new areas because they’re following warm bodies of water,” said Maxine Montello, Rescue Program Director at the New York Marine Rescue Center.

Human and Animal Interactions

Another aspect of the increased dolphin sightings has to do with public perception. The New York Marine Rescue Center and other conservation organizations have worked hard to increase public awareness about local animal life. With the COVID-19 pandemic, people have been outside more, utilizing their local natural resources in new ways, and consequently reporting more wildlife sightings.

“We’re seeing a huge overlap with humans and animals,” said Montello. The New York Marine Rescue Center gets calls all day from their twenty-four-hour hotline, not just of stranded animals in need of assistance but reports of healthy animals. “When you have dolphins overlapping with a highly populated area like that Montague, for example, we get a lot of phone calls just about that population,” said Montello.

Along with the hotline, the Department of Environmental Conservation has created a survey for marine mammal and sea turtle sightings called “Flipper Files.” Montello said the use of these new technologies makes it easier for people to record sightings because they can just do it on their phone.

The Marine Mammal Protection Act, a federal law enacted in 1972, has also contributed to the uptick in population. The law limits human interaction with marine mammals and prevents the “take” of marine mammals such as hunting, harassment, capturing, and killing. The law has significantly aided in the stabilization of many marine populations in New York harbor.

As New York’s waters become healthier more animals will be around. That means educating the public about safe boating practices and limiting human-animal interactions will become more important. “New York is amazing with our unique waters and the animals that come here,” said Montello. “With that, we need to be able to keep them here.”

If you see a marine mammal report it to the Department of Environmental Conservation through their online survey ( or call The New York Marine Rescue Center’s hotline at 631-369-9829.