A harbor seal pup that attracted a crowd of onlookers to the shore of Portland’s Back Cove on Tuesday was euthanized because it was considered too sick to be transported to an out-of-state rehab facility.

“It definitely was dealing with some respiratory issues … a respiratory infection, and I think it was getting worse,” said Lynda Doughty, executive director of Marine Mammals of Maine, a nonprofit response-and-rescue group based in Boothbay. “It wasn’t going to survive trip to Mystic, (Connecticut).”

The three- to four-month-old pup appeared to be resting at the edge of Back Cove, next to Interstate 295, for a few hours from Tuesday morning into the afternoon. It was just feet from a popular trail around the cove, and attracted a steady flow of admirers and people who feared for its health.

Marine Mammals of Maine sent a volunteer to observe the seal and protect it from people or pets who might get too close.

Seals usually come onto shores and beaches just because they are tired and need rest, and they typically aren’t removed unless they are sick, injured or in danger.

Bill Barthelman watched over the seal until it began coughing and gagging, then wrapped it in a towel, put it in an animal carrier and took it away to be examined by Doughty.

Doughty is licensed to examine stranded marine animals, but Maine no longer has a licensed rehabilitation facility where sick or injured animals can be nursed back to health.

The University of New England’s Marine Animal Rehabilitation Center in Biddeford, which had helped more than 1,000 stranded or injured marine animals since 2001, closed this summer because of budget cuts by the school. Now, the nearest rehab centers are in Massachusetts and Connecticut.

Doughty’s organization, which has about 60 volunteers who respond to abandoned seal pups and stranded marine mammals from Kittery to Rockland, used to take most its sick or injured animals to UNE. The group has an agreement that allows it to take some seals and turtles to the Mystic Aquarium’s rehab facility in Connecticut, but that facility has limited space and the longer trip is too difficult for some distressed animals to endure, Doughty said.

“We’ve been able to transport some (animals to Connecticut), but we really have had to prioritize,” Doughty said.

If UNE’s center had been open Tuesday, she said, “we would have brought it right to Biddeford. (The seal) was in tough shape, but it would have had a shot.”

Doughty said there are still no solid plans to replace the UNE rehab facility in Maine. “We need funding and we need the (facility and) permits to do rehab. … We don’t want to be in this predicament.”

Seals like the Portland pup keep the group busy, but they aren’t the only animals that trigger calls.

On Tuesday night, Doughty responded to a beached 19-foot-long pilot whale on Popham Beach. The adult male whale died shortly after responders arrived. Doughty said a necropsy will be done in an effort to figure out why it got stranded and died.