A new study shows that from spring to autumn New York Harbor is a feeding ground for bottlenose dolphins

Bottlenose dolphins arrive in New York Harbor in the spring and often walk on busy waterways throughout the fall, sometimes feeding on such frenzy that their food-clicking clicks sound like buzzing on underwater listening devices in Brooklyn, Queens, Staten Island and New York. -Jersey.

“We see dolphins regularly,” said Howard Rosenbaum, director of the Ocean Giants Society’s Ocean Giants program and a senior researcher at the New York Aquarium. “I think it’s interesting that you can see them quite often when you’re on the beach. It’s not all the time, and it may not be the right time of day when you watch, but we see them regularly. “

A study published this month by the Wildlife Conservation Society, based on passive acoustic monitoring from April to October 2018 to 2020 at the mouth of New York Harbor, New Jersey, found that dolphins arrived for food in an ecosystem rich in more than 200 species. fish, most often in late summer and early fall.

The estuary is located where the Hudson, Hakensak, Passai and Raritan rivers meet the ocean in the most populous metropolitan region of the country.

The dolphin “belongs to the northern migratory coastal part of the West North Atlantic,” said Sarah Traby, a researcher at the Wildlife Conservation Society and lead author of the study.

Its research team included Rosenbaum and three other scientists from the Conservation Society, as well as a researcher from the University of California at Santa Cruz.

The research grant from the Hudson River Foundation, Traby said, was originally intended to collect and study baseline data on large whales that have been spotted in the mouth, such as tea.

The Society for the Conservation of Wildlife has collected data on whales through passive acoustic monitoring, but has also recorded the detection of dolphins on these listening devices, Traby said. Given this, the Environmental Society has decided that a study on dolphins is justified, she said.

“It’s interesting because it’s establishing baseline data for this dolphin population that we really don’t know much about,” Traby said. “In fact, many New Yorkers don’t know that there are dolphins right off the coast of New York.”

Although society has seen dolphins in the mouth for years, the research team noticed an increase in the number of dolphins that seemed to linger for longer periods of time.

What will bring dolphins to New York Harbor? Traby said it was now a million-dollar issue. She is interested in the fact that they come here, especially since the river and near it are very active, including shipping and the coast.

“I think people in general don’t associate New York water with the diverse, the ecological, the environmentally rich, important to species like marine mammals,” Rosenbaum said. “Over the last decade or so, we’ve seen some pretty important changes in terms of some species, such as dolphins and whales, that are increasingly using these habitats as a suitable breeding ground for these animals.”

Trab also has theories about prey, which is also a source of food for dolphins. The team did find a match in space and time between a large number of Atlantic menhaden, prey species, and a large number of dolphins.

“At a time when the Atlantic menhaden is in the largest numbers, we also see that dolphins are in the largest numbers, but it’s very speculative,” Traby said.

The estuary is one of the most productive and diverse natural systems on earth, and the abundance of species in the estuary of New York Harbor New Jersey is a good example of such biodiversity. According to NY / NJ Harbor Baykeeper, it has more than 200 different species of fish and more than 300 species of birds.

Traby and her team found that dolphins fed most of the time when they were in the harbor, suggesting that the estuary is an important place for them to feed.

Concluding the study, the Wildlife Society determined when dolphins were present, which was important for establishing baseline data not only on when they were in the harbor, but also on what environmental variables were associated with their presence and when they were feeding. .

Rosenbaum said this is important to establish as the development of offshore wind farms, the main new source of renewable energy, is going on in New York waters.

“It’s so important to our planet, to our society, to our climate, that the state and the federal government have set out to deliver energy to all the millions of people and homes in this urbanized area,” Rosenbaum said.

But the Wildlife Society, he said, wants this development to be carried out in the most environmentally responsible and sensitive way, especially if it could affect the well-being of these iconic, protected and critically endangered whales and dolphins.

Although Traby and her team did not analyze how dolphins behave in urban environments, she was able to draw some conclusions: dolphin clicks looking for food are sharply reduced, for example, during times of intense navigational activity in the harbor.

“We have much less dolphin detection,” Traby said. “Although we can’t say because of shipping that there are fewer dolphins because we haven’t analyzed it. We can say that in this area, where there is a lot of shipping, we have had less dolphin detection ”.

The Wildlife Conservation Society could conduct this study because dolphins echo the sound and then use the echo of that sound and the time of that echo to get a distinctive image of their surroundings and their prey.

When dolphins search for fish, the closer they get, the more clicks they give out, which tells them they are getting closer to their prey.

“In fact, when they get closer to the subject of mining, you can imagine that they want to get a better picture of their mining with a higher resolution,” Traby said. “So as this dolphin approaches, they emit clicks faster and faster, with less time between clicks so they can hear the echo and sort of hone where this prey is in space and time so they can take and consume.”

Traby and her team collected time between clicks as data. As the dolphins got very close, their clicks began to sound like a buzz, she said. So Traby and her team looked at the buzzing of the stern and the time between the clicks that were caught by the microphones.

With these benchmarks in mind, Rosenbaum said, the Wildlife Society can work with a variety of stakeholders to recommend best practices and mitigation measures that will help reduce the risk or harm to bottlenose dolphins.

“Now that we have this information, we need to work as a scientific conservation organization with all the different industries and different regulators to make sure we use the information effectively to best protect these animals,” Rosenbaum said.