The buoy with satellite tracking gear that had been attached to an entangled North Atlantic right whale was recovered late Friday, leaving rescuers with only the hope that the mammal would be spotted again.
A fishing vessel picked up the buoy as it was trawling Friday, and carried it into a New Jersey harbor.
The 34-foot yearling whale was first spotted off the coast of Florida on March 19 and had moved north since then.
Scientists did manage to attach a buoy with a satellite transmitter that was used to track the whale, dubbed Kingfisher in honor of the Coast Guard cutter that helped out off Florida.
Scientists are concerned that the lines will kill Kingfisher by tightening around the creature as it grows. In addition, the lines restrict its ability to dive deep for food. Scientists believe Kingfisher is one of only about 300 North Atlantic right whales in the world.
Kingfisher had been coming in and out of the Gulf Stream, the powerful oceanic current that moves north along the North American coastline.
North Atlantic right whales are the most endangered whales off American coasts. They are listed as endangered under the U.S. Endangered Species Act.
Experts unsuccessfully tried a similar rescue in July 2001 off the coast of Cape Cod, Mass. That whale never slowed long enough for ropes to be cut and experts eventually lost track of it in bad weather. Its status is unknown.
The Center for Coastal Studies, based in Provincetown, Mass., said saving entangled whales is entirely practical, noting that it has done so in 60 cases since 1984.