Scientists unsure of cause of seal illnesses Warm weather, normal attrition are suspected.

February 19, 1992|By Frank D. Roylance | Frank D. Roylance,Staff Writer

A Canadian scientist says unseasonably warm winter weather is a possible factor in the mysterious strandings or deaths of more than 300 ailing harbor seals over the past year on beaches from Maine to Virginia.

Other observers say the increased number of strandings -- including two since Dec. 29 in Maryland -- may reflect normal attrition in a population that has boomed in the Northeast since seals came under federal protection in 1972.

Dr. Joseph Geraci, a wildlife biologist and marine mammal expert at the Ontario Veterinary College in Guelph, Ontario, said he and other scientists investigating the strandings haven't pinpointed the cause of the illness that is bringing the animals ashore, dying or too weak to swim.

Dr. Geraci, a consultant to the National Aquarium, was in Baltimore last week where he examined the latest arrival, a malnourished harbor seal. The male pup, 7 or 8 months old, was brought to Baltimore Feb. 7. The pup is being tube-fed and treated for lungworms.

Warm weather, like that occurring this winter and last, was linked statistically to a similar rash of seal strandings in 1980 and it's now "something we've been thinking about" to explain the current phenomenon, Dr. Geraci said.

In 1980, he said, at least 500 harbor seals sickened and stranded on Cape Cod, Mass., in an epidemic traced to an influenza virus. But laboratory tests indicated the virus by itself couldn't account for the high number of deaths.

Scientists say that when the air is colder than water temperature, seals normally stay in the water. Mild weather encourages them to "haul out" on coastal beaches. Crowded conditions ashore then may facilitate the spread of airborne viruses, such as influenza.

Federal officials said a similar, but smaller die-off occurred during the unusually mild winter of 1985-1986, and also was blamed on an influenza virus.

Three seal pups suffering from pneumonia, parasites, malnutrition and minor injuries have been brought to the National Aquarium in Baltimore since Dec. 29 after strandings near Virginia Beach, Va., at Ocean City, Md., and on Maryland's Assateague Island -- far south of their traditional range.

One of the pups died, and one was treated and sent to the New England Aquarium to await release. One still is being treated.

Dr. Geraci said examinations of more than 150 seals stranded in New England revealed a variety of ailments, including pneumonia, liver disease and skin lesions.

To Dr. Geraci, that suggests some common underlying cause, such as a virus.

P. Michael Payne, of the National Marine Fisheries Service in Silver Spring, said harbor seal populations in New England have grown since state bounties were lifted in the 1960s and federal protection was extended to seals under the 1972 Marine Mammal Protection Act.

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