Rio Vista, Calif. ? Everyone seems to have a suggestion to get two wayward whales lingering in the Sacramento River to swim 70 miles back to the Pacific Ocean.

One person suggested towing life-sized replicas of orcas behind the whales to scare the recalcitrant mother humpback and her calf.

Another proposed placing a giant magnet downriver, since humpbacks are thought to navigate by an internal compass that can sense magnetic north.

On Saturday, veterinarians on a boat shot custom-made syringes with 8-inch needles at the whales in what wildlife officials said was the first time antibiotics have ever been administered to whales in the wild. The treatment is meant to ward off infection in deep wounds that have worsened from long exposure to fresh water.

While rescuers have not tried the hundreds of suggestions they have received via e-mail – most of which are unfeasible – they acknowledge that they are running out of ideas.

“This is very much a work in progress,” said Trevor Spradlin, a marine mammal biologist with the National Oceanic and Atmospheric Administration working at the rescue scene.

More than two weeks after the whales were first spotted in fresh water, the giant mammals continued to circle in the river. Their once smooth, shiny skin has become dull and rough, and tissue around the gashes likely inflicted by a run-in with a boat was starting to die off, biologists said.

Scientists hastily drew up plans to spray the whales with fire hoses Friday after nearly a week of pipe-banging and whale recordings failed. Scientists used recordings to nudge a male humpback dubbed Humphrey out of the Sacramento-San Joaquin River Delta in 1985.

The pair got stranded after marking an apparent wrong turn earlier this month and heading upstream until they reached the Port of Sacramento and could go no farther. They turned around on their own Sunday, and swam some 20 miles downriver to the Rio Vista Bridge.

The central problem facing scientists trying to engineer new whale-herding techniques is that, while gentle coaxing has proved ineffective, they fear anything too forceful might make the situation worse. Nets pose a threat of entanglement, biologists said.

Any method that induces panic could separate the whales or send them fleeing, increasing the danger they could become stranded in the mud among the delta’s labyrinthine network of sloughs, they said.

During the week, rescuers grew concerned that some of the tactics they tried may have been too stressful for the duo. Some onlookers complained that scientists should stop interfering with the whales and allow them to follow their natural instincts.