As the number of dead or stranded live seals washing up along the coast from northern Massachusetts to southern Maine continues to increase dramatically, marine mammal experts are considering influenza or environmental pollution as potential explanations.
Although there is no definitive cause for the uptick in seal deaths — with the count now over 400 this year — the Seacoast Science Center, in Rye, New Hampshire, is continuing to test tissue from fresh seal carcasses to determine if there is a possibility of illness. Live seals have been found in poor condition with signs of lethargy, coughing, sneezing and having seizures, according to Jennifer Goebel, a spokeswoman for the National Oceanic and Atmospheric Administration.
NOAA, a scientific agency which focuses on the conditions of the oceans, major waterways and the atmosphere, released an updated number of seal strandings and deaths Tuesday morning, primarily gray and harbor seals.
In New Hampshire and northern Massachusetts, marine mammal specialists found 15 live and 26 dead seals in July. As of Aug. 20, they had found 14 live and 31 dead seals in the same region. As of the same date, 57 dead seals have been accounted for in New Hampshire and Massachusetts, according to NOAA statistics. Four seals, three babies and one adult, were reportedly found dead on Plum Island in the last week.
NOAA scientists totaled 404 dead and live seals when examining all seals found on the shoreline in Maine, New Hampshire and Massachusetts.
When examining data from previous years, Goebel said these numbers are abnormally high. In 2017, 135 live and dead seals were found in Maine; 43 in New Hampshire; and 24 in northern Massachusetts, according to NOAA scientists.
When examining causes for this uptick in seal deaths, which is now being labeled as a “die-off” by scientists, Sarah Perez, a marine mammal rescue assistant working with Seacoast Science Center, said samples are being collected and sent for testing for avian influenza and phocine distemper virus. Results, she said, should be available next week.
According to NOAA, previous instances were numbers of seals were killed have been caused by avian influenza and phocine distemper virus in the Northeast. With input from the experts, NOAA’s response team is taking a tiered approach relying on pathology and epidemiology “to guide the direction additional analyses may need to go as we rule in or out physical, chemical or biological factors that may be contributing to or causing these mortalities,” Goebel said.
Many of the carcasses have been found in various stages of decomposition across all age groups, she added.
Southern Maine continues to see the greatest number of dead seals washing ashore. Along the coast of Maine, NOAA counted 43 live and 65 dead seals in July and 40 live and 170 dead seals in August. In total, 235 dead seals have been found in Maine since July 1.
In an interview with The Press Herald of Portland on Aug. 19, Susan Shaw, a marine biologist based in Blue Hill, linked the sudden die-off to decades of chemical pollution that made the seal population vulnerable to disease and toxins, specifically polychlorinated biphenyl, or PCBs. The long-term health effects of PCB on harbor seals show that the populations of these seals in the Gulf of Maine are loaded down with toxic, immune-suppressing chemicals, said Shaw in an interview with The Press Herald.
Shaw, the founder of the Shaw Institute – formally the Marine and Environmental Research Institute – has been studying toxins in seals and other marine animals since 2000.
A high level of exposure to PCBs among harbor seal pups was one of her first findings, according to the article.
Milton Levin, a professor at the University of Connecticut who studies the effect of pollutants and toxins on marine animals, told The Press Herald that years of research have aligned with Shaw’s findings.
“The weight of evidence suggests that animals that are exposed to different environmental contaminants, somehow that modulates their immune system, (and) that may make them more susceptible to viral or bacterial diseases,” Levin told the newspaper.
Since PCBs are hard to metabolize, the contamination passes down through generations of seals, Shaw said.
“It’s a well-known fact that those chemicals do stem in all marine mammals,” said Goebel. “It’s possible it could be some kind of contributing factor.”
Further evaluations will continue as new cases develop or new evidence changes the direction of the investigation, according to NOAA officials. For the safety of beach goers and seals, NOAA ask people not to touch a stranded seal and to not let pets approach the seal.
The seal should be observed from a safe distance of 100 yards, Goebel added. If you come across a live or dead seal, call the Marine Mammal Rescue Team Hotline, 603-997-9448.
