NEW BRUNSWICK, NJ—A group of dolphins apparently made their way into the Raritan River this week, attracting onlookers from New Brunswick and Highland Park.
Their appearance could be viewed as one sign of improving conditions in the Raritan River, but it also raised concerns about the health of the dolphins, who may have found themselves trapped in the shallow water.
This reporter recorded several of the sea creatures swimming in a “pod” near the Albany Street Bridge on the evening of April 11.
Knowledgeable sources tell New Brunswick Today that it is unusual for the dolphins, which are abundant in the Northwest Atlantic Ocean, to be found in inshore waters and rivers.
“The dolphins observed in the Raritan River have been confirmed as common dolphins (Delphinus delphis),” said Andrea Gomez of the National Oceanic and Atmospheric Administration (NOAA), a part of the US Commerce Department. “This species of dolphin is a highly social species, found in large groups (or pods) and commonly found in offshore waters, but also seen nearshore at certain times of the year.”
“Annually, we do receive reports of dolphins that venture into river systems throughout the region. In some cases, they are chasing prey, but in other cases the reason for their movements into rivers is unclear.”
While the dolphins showed no signs of distress as they splashed and swam in the Raritan, there is some cause for concern about their safety if they don’t make their way back to the ocean soon.
Concerns stem from the possibility that the dolphins could find themselves stranded, as they are the “most common species to mass strand” in the Northeast, according to Gomez.
“It’s an ongoing situation and we’re on top of it,” said Denise, a woman who answered the Marine Mammal Stranding Center’s 24-hour hotline on April 13. The pod was last seen on April 12, according to the center.
Other concerns stem from the lack of salt in the Raritan River water, and the potential for low oxygen levels there.
“Extended exposure to freshwater environments can cause skin lesions on dolphins, and other potential direct and indirect impacts. However, it takes weeks, sometimes months in freshwater environments before these types of symptoms start to occur,” said Gomez.
“Low oxygen conditions at this time of year are not very common in most East Coast rivers. If the lack of oxygen results in a fish die-off that could encourage the dolphins to move out of the river to find food.”
The NOAA spokesperson expressed that boats could pose a threat as well: “As the animals move closer to shore, they are more likely to be near people and boats. This can pose dangers to them, as some animals have been harassed or hit by boats.”
New Jersey officials had much less to say, acknowledging the situation but referring all questions to NOAA and the MMSC.
“Fish & Wildlife is aware of dolphins in the river,” said Larry Hajna, a spokesperson for the NJ Department of Environmental Protection, referring to a division in the department.
It’s not the first time a dolphin has come to Middlesex County.
In 2015, an older dolphin of a different species—the bottlenose dolphin—delighted locals as it swam in the South River near East Brunswick and Old Bridge. But it died after getting trapped in shallow water, and a a rescue effort failed to save its life.
The state government initially tried to keep secret the results of a necropsy performed on the dolphin, with the NJ Agriculture Department citing the dolphin’s medical confidentiality, before ultimately releasing the reports.
Despite concerns for the safety of dolphins who ended up in New Brunswick, NOAA typically says the best response is to give the animals space, and that “attempting to capture and relocate free-swimming animals may cause much more harm than good”
“Letting nature take its course is the best course of action with the least risk to the safety and welfare of the dolphins and our stranding network partners,” reads a 2021 article published by the administration about the appearance of bottlenose dolphins in Monmouth County’s Shrewsbury River.
The article concluded that the presence of the dolphins in both the Shrewsbury and Navesink Rivers indicated a healthier environment, and increased fish population.
Charlie is the founder and editor of New Brunswick Today, and the winner of the Awbrey Award for Community-Oriented Local Journalism. He is a proud Rutgers University journalism graduate, a community organizer, and a former independent candidate for mayor of New Brunswick.