SAN FRANCISCO -- Scientists testified Friday in federal court that they do not expect whale-finding sonar to affect the behavior of migrating gray whales or to harm them.
The scientists testified that the noise the sonar made will likely be inaudible to the whales as they make their way down the coast from Alaska to Baja California.
One scientist who testified was from the government, one was from a private research institution and the third runs a company that makes the sonar equipment.
But environmentalists, who are trying to get a judge to block the use of the sonar, brought in their own scientist who said the sounds could cause stress to the animals, particularly mothers and calves and pregnant females.
The environmental groups sued after learning that Peter Tyack of the Woods Hole Oceanographic Institution in Massachusetts planned to use the sonar to see if it could detect whales on their migration.
The National Marine Fisheries Service approved the experiments last year, but earlier this month, U.S. District Judge Samuel Conti temporarily blocked the experiment.
If Conti allows the testing to proceed, it may still be on hold until next year. Peter Stein, who runs Scientific Solutions, Inc., of New Hampshire, which makes the sonar, said the scientists have until Jan. 29 to conduct the experiment.
Conti's temporary block of the experiment was the third time in as many months that a San Francisco federal judge has halted underwater sound testing over concerns about marine life.
The judge said he may rule on the sonar case within a week.
The sonar, while still in its experimental stage, is being touted as a benefit to whales, because it's a possible way for organizations know if there are marine mammals in the vicinity of underwater operations that might harm the animals.
For example, the sonar could keep vessels from ramming the creatures and oil explorers who detonate undersea explosives could use the sonar to detect if whales are nearby. Currently, much of the detection of marine mammals is done by human eyesight, but is only effective when the animals are at the surface, he said.
The environmental groups say the high-frequency sonar could disorient the whales and separate the calves from their mothers during migration.
Tyack said the sound from the sonar is about as loud a sound as the whales make themselves, and that the animals are exposed to noise from other sources.
''The ocean is a very noisy place,'' he said. ''They're hearing other whales; they're hearing the surf.''
But Conti wondered if the sonar wouldn't exacerbate the effect of other human-made noises on whales. ''Could we be the straw that broke the camel's back?'' he asked.
''The more stressors you have -- it's greater than the individual stresses,'' said Albert Myrick, Jr., a retired scientist brought in as an expert for the plaintiffs.
In October, a federal judge in San Francisco ordered the National Science Foundation to stop firing high-intensity sonic blasts into the Gulf of California because they harm whales.
And in November, the U.S. Navy agreed to temporarily scale back the testing of a new sonar system designed to detect enemy submarines after a federal magistrate halted the project.
The judge said a similar Navy sonar may have caused at least 16 whales and two dolphins to beach themselves recently on islands in the Bahamas. Eight whales died and scientists found hemorrhaging around their brains and ear bones, injuries consistent with exposure to loud noise.
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