Two dolphins sighted for the first time in the Shrewsbury River almost two months ago are still there, heightening the level of concern among some experts who fear the mammals might not be able to make it out of the river on their own.

Dipping water temperatures have some marine mammal experts calling for a full rescue of the two bottlenose dolphins, believed to be a mother and a calf.

The dolphins were spotted in the river again on Sunday, said Robert Schoelkopf, director of the Marine Mammal Stranding Center in Brigantine, adding that he has sent rescue plans to the National Marine Fishery Service in Gloucester, Mass., asking that they intervene and remove the dolphins from the river.

"The water temperatures have dropped dramatically," said Schoelkopf. "When the temps go below 60, it becomes more critical and the dolphins have to use more body fat," he said.

Earlier this week, the temperature in the river averaged about 50 degrees.

Next week, the fishery service and volunteers from the stranding center will attempt to use an underwater sound device attached to fishing net that lets off an annoying sound, to try to get the dolphins to head north out of the river.

The device, called pingers, lets off a loud chirping sound, said Schoelkopf, and is commonly used in the New England area to keep dolphins and seals out of specific areas.

The dolphins apparently navigated their way into the Shrewsbury River accidentally while heading south. They have been spotted in the southern most part of the Shrewsbury River close to Monmouth Beach.

Schoelkopf explained that once the dolphins get off track and enter the Raritan Bay, they tend to continue heading south, leading themselves further into the river.

"They don't know they have to go 10 to 12 miles north before they can go south again," Schoelkopf said.

Their presence has captured the attention of several agencies, especially in light of a 1994 incident in which four dolphins died after becoming trapped in the icy Shrewsbury River. Rescuers had battled frigid weather and snowstorms for days in an attempt to cut an escape route through thick ice, but it was a futile attempt.

"We don't want a repeat of that," said Schoelkopf. "We've been trying to convince the fishery to do something. It's been over two months."

The National Marine Fishery Service determines whether there is cause to remove the dolphins. In 1994, the fishery service came under attack from some mammal experts who argued that the Fishery Service waited too long to try to get the dolphins out of the river.

Dana Hartley, the National Marine Fishery Service stranding coordinator, said experts are monitoring the dolphins. At this point, there is no definite plan in place to rescue them.

"We are concerned about the welfare of these animals, but at this point, they do not appear to be in danger," Hartley said. "NMFS is not likely to intervene or to authorize intervention unless the dolphins remain in the river as the weather turns colder and the food fish leave the area."

A team of biologists have observed the dolphins, said Hartley, and they found that the animals are apparently feeding on a plentiful supply of fish, particularly menhaden. The dolphins show no visible external wounds or apparent respiratory problems and are swimming strongly, she said. "The abundance of food fish may be the reason the dolphins haven't left the river," Hartley said.

But Schoelkopf said that although the dolphins are in an area with a lot of fish food, it isn't guaranteed that they are eating. In the meantime, he said, the stranding center and the fishery service have received letters and calls from people asking that the dolphins be rescued.

"Our hands are tied," said Schoelkopf, adding that the center doesn't have the staff and equipment necessary for a full net rescue, and that the fishery service has the facilities needed to capture them.