Delta and Dawn The whale story of Sacramento

Kcra3 reports

RIO VISTA, Calif. -- Herding efforts to direct the wayward humpback whales in the Delta back to the Pacific Ocean have been suspended in favor of a new set of underwater audio.
At a 3 p.m. press conference on Wednesday, Trevor Spradlin of the National Oceanic and Atmospheric Administration said the strategy is to play a different set of sounds for the animals.
The first clip is audio of humpback whales feeding in Monterey Bay, the other is audio of killer whales attacking gray whales. Other sets of audio are man-made tones, which may sound unusual to the whales.
NOAA will reassess the effectiveness of the new techniques on Thursday to determine procedures for the weekend. If the new set of audio proves to be ineffective, the rescue efforts will be reduced to an observation period through Monday.
Authorities are also concerned about the impact of hordes of boats expected on the water during the upcoming Memorial Day weekend. A 500-yard safety zone has been established around the whales.
Deep cuts on the mother whale and her calf, likely caused by a run-in with a boat, were worsening after more than a week in freshwater surroundings that the pair were not physically well-equipped to inhabit, biologists said.
"I wouldn't say there's a lot of optimism right now," said Brian Gorman, a spokesman for the National Oceanic and Atmospheric Administration.
"They may surprise us again. They may just take off and head down river. But as long as they continue doing what they're doing, we're very worried about them."
Two humpback whales that have wandered in the Delta for more than a week swam nearly as far downstream as the Rio Vista Bridge on Wednesday before heading a short distance upstream.
The whales have drawn intense interest since they were spotted near Rio Vista on May 13. The animals, which normally live in the salt water of the open ocean, are in fresh water about 70 miles inland from the Golden Gate.
Meanwhile, officials are worried that the health of the mother, named Delta, and the calf, called Dawn, may be deteriorating and that injuries to both animals do not appear to be healing.The animals were spotted at about 6:30 a.m. Wednesday just north of the Sacramento River in Cache Slough, roughly the same place they were last seen on Tuesday.Boats were used once again in an effort to herd the mammals downstream. Some boats are fitted with pipes that are partially submerged in the water. People on the boats bang the pipes with hammers, sending out sounds through the water that are intended to drive the whales away. -->
The whales swam downstream Wednesday morning to an area a couple hundred yards from the Rio Vista Bridge before turning around and returning to waters just off the Ryer Island ferry as of noon.
Officials said they were hoping that the incoming tide Wednesday morning would encourage the whales to head back toward the ocean, especially since the animals seem to enjoy swimming against the flow. But that did not appear to make a difference.
The whales were first spotted in the Delta on Mother's Day. They then swam from the Sacramento River up the deep water shipping channel to the Port of Sacramento, where thousands of people gathered on a nearby levee to see them swim.
On Sunday afternoon they headed back down the channel and by early Monday they were near Rio Vista. Since that time, they have been swimming in an area north of the Rio Vista but south of the shipping channel.
For more information about the whale rescue, please e-mail sacramento.whale@noaa.gov.