MARINE biologists in California will tomorrow resume efforts to herd a pair of injured humpback whales back to the Pacific Ocean after they strayed down the San Joaquin river delta to the city of Sacramento, almost 100 miles inland.

The plight of the whales, a mother and calf, has captivated California and was expected to draw thousands of onlookers to the levees around a murky waterway close to Sacramento’s Capitol building, the seat of state government.

Both whales are believed to have been hit by a boat propeller after they wandered off their normal migratory course northward from waters off Mexico. They passed under San Francisco’s Golden Gate Bridge and would have encountered heavy shipping traffic as they headed further inland.

Initial attempts to persuade them to swim back the way they came have so far proved unsuccessful. Among whaling experts joining the rescue effort was Bernie Krause, a so-called “whale whisperer” who lowered loudspeakers into the water and played recorded whale noises.

Krause’s recordings had played a key role in the 1985 rescue of a humpback whale nicknamed Humphrey, who had followed a similar route up the Sacramento delta. Krause, an electronic audio specialist who helped develop the Moog synthesizer, managed to lure Humphrey back down the river using sounds he had recorded off the Alaska coast.

Last week he was less successful as the two whales reached a dead end in the channel. They have since been swimming in a deepwater basin used by ships for turning around.

Humphrey survived for 26 days before he was eventually lured to safety and scientists said last week they were in no hurry to move the latest arrivals, both of whom bear visible gashes from their encounter with a propeller.

Rescue operations were suspended this weekend to allow the whales time to recuperate. “We really do not want to stress the mother and her calf in any way,” said Frances Gulland of the Sausalito-based Marine Mammal Center, which is assisting with the rescue.

US coastguards were keeping sightseeing boats at a distance, and the channel and basin have been closed to commercial shipping traffic.

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