Officials Report Spike in Bottlenose Dolphin Deaths This Summer

Dolphin strandings and deaths have been seven times higher than the historical average over the past month in the mid-Atlantic region.

So said the National Oceanic and Atmoshpheric Administration in a release, which declared an Unusual Mortality Event for bottlenose dolphins in the area from early July through the present.

NOAA officials said "elevated strandings" of bottlenose dolphins have occurred in New York, New Jersey, Delaware, Maryland and Virginia.

NOAA officials added that while "there are no unifying gross necropsy findings," several dolphins have been found with pulmonary lesions.

Preliminary testing of tissues from one dolphin indicated a possible morbillivirus infection, "although it is too early to say whether or not morbillivirus may be causing this event," the release stated. "Based on the rapid increase in strandings over the last two weeks and the geographic extent of these mortalities, an infectious pathogen is at the top of the list of potential causes."

All potential causes for the deaths will be evaluated and work is ongoing to determine whether an infectious agent affecting the dolphins is present in tissue samples.

An independent team of scientists is being assembled to review the data collected and to determine the next steps.

All age classes of bottlenose dolphins are involved and strandings range from a few live animals to mostly dead animals with many very decomposed, NOAA officials added.

In July, a dolphin washed ashore in Long Beach, the third mammal of its kind found along the city’s shore in recent days and among a growing number of fatalities of a particular species over the summer summer.

“There were no outward signs of being struck or injured,” a resident wrote in an email about the mammal’s appearance.  

The Riverhead Foundation for Marine Research and Preservation retrieved the bottle-nose dolphin in Long Beach, as well as another of the same species in Rockaway, and conducted an autopsy on both creatures.

Kim Durham, a Riverhead Foundation rescue program director who performed the procedures, said the dolphin found in Long Beach was a male, approximately a year old, which suffered from a respiratory disease.

“It did have a pretty significant lung infection and it was very underweight and had an empty stomach,” said Durham, who added that she took tissue samples from the animal which, through further tests, could reveal the source of the infection.

The dolphin retrieved from Rockaway, she said, was a male that had parasites and adhesions within its intestinal tissues, “which is evidence of a chronic infection."

Meanwhile, two other dolphins were found on local beaches. Of the latter dolphin, tides took it back out to sea before it could be retrieved, but photos revealed it was not the same dolphin found in Long Beach, Durham said.

Earlier in July, a basking shark washed ashore on a West End beach in Long Beach, and a dolphin that was stranded near Jones Beach died. Next, the Riverhead Foundation was informed that two more dead bottle-nose dolphins were discovered, one in Breezy Point and the other in Fire Island Inlet.

Durham reported a marked increase in dolphins that have washed ashore this summer, not only in New York but also in New Jersey and Virginia. While the agency in New York responded to three dolphins that washed ashore from June 23 to July 31 in 2012, that number for the same time period this summer had jumped to 15.

Durham called the increase “a big difference,” but was quick to note that it could have multiple causes, which the agency has yet to determine.

On examining a washed-up bottlenose dolphin, Durham said, she first tries to determine whether the mammals demise was due to a natural fatality or a byproduct of a fishery interaction, usually when an animal gets ensnared in a fishing net, before looking for indications of disease.

Durham said people typically point first to water quality as the possible cause of washed-up dolphins and other sea creatures. But other potential factors, including viral or bacterial infections unrelated to the water, as well as an increase in the mammal population, could explain the increase. She said that a whale-watching organization has reported a significant increase in whale and dolphin sightings in New York Harbor this year. 

Because of such reports, she is not alarmed yet by the increase number of dolphin deaths.

“If the population is big, then you’re going to see a certain percentage of that population that is going to be sickly, whether it be of the young or the old,” she said. “Right now we’re trying to figure out whether there is anything connecting all of the animals [that have washed up], and so we have our hands full with that.”

The Riverhead Foundation asks that anyone who spots a dolphin or other marine mammal that has washed ashore to call the agency at 631-369-9829.

With reporting by Joseph Kellard.