The bottlenose dolphins, including two calves, have been in the narrow Shrewsbury River for about 2½ weeks, possibly after making a wrong turn chasing schools of bait fish.
Wildlife authorities are concerned that heavy boat traffic on the river - which will be even heavier over the July 4 weekend - could endanger the dolphins. But as of now, there are no immediate plans to try to move them, said Teri Frady, a spokeswoman for the National Oceanic and Atmospheric Administration.
"What we're looking for is a situation where the risk of them staying where they are outweighs the risk of moving them," she said. "They are out there again today, feeding and socializing. They look fine."
Thunderstorms that moved through the region over the weekend did not scare the animals out of the river and into open water, as officials hoped they would.
Environmental officials and volunteers are considering various plans to try to either lure or scare the dolphins out of the river into Sandy Hook Bay and out into the ocean. But each poses potential problems, including stressing the animals, Frady said.
A team of experts from as far away as Massachusetts and North Carolina is being assembled and could be deployed on the river this week if conditions worsen for the dolphins.
But even that might not work; authorities said last week they are afraid that rather than being herded out to deeper water by rescuers' boats, the dolphins might just dive deeper in the river to avoid them.
Lone dolphins and smaller groups have periodically entered the river and gotten out on their own, but this is by far the largest group that has been seen in the Shrewsbury in recent memory.
In 1993, authorities tried to remove dolphins that had spent the summer and fall in the river. When the river froze, attempts to shoo the animals out to sea only chased them under the ice, where several drowned.
