Only five of the 16 bottlenose dolphins were spotted Monday and Tuesday in the Shrewsbury River, and none in the Navesink.
And more are expected to die or strand themselves this winter.
That's spurred the animal rescuers to renew their calls to have the dolphins removed or coaxed out of the rivers and back out to sea.
But the National Oceanic and Atmospheric Administration, which has jurisdiction over the dolphins, still refuses to permit a rescue or relocation attempt.
The agency says it's possible that as many as eight dolphins have made it out to sea on their own, but cautioned that can't be proven.