Concern grows as stranded whales circle

May 23, 2007, 5:02 GMT

San Francisco - Concern grew Tuesday for the health of two humpback whales stranded in a California river, as the mother and calf circled for a second day at a bridge 120 kilometres from their natural ocean habitat.

Researchers said that the mother humpback in the Sacramento River showed the first real signs of stress Tuesday, rolling quickly from side to side in what observers described as a thrashing movement.

'We are concerned that she is getting increasingly stressed,' said Frances Gulland, a veterinarian with the Marine Mammal Centre, who was aboard a boat tracking the whales, dubbed Delta and Dawn.

Gulland added that there have been changes for the worse in the whales' propeller wounds and skin condition.

The mother and calf began the long swim Sunday from the Sacramento Port about 160 kilometres from the ocean after resisting scientists' attempts to lure them to the ocean using recordings of whale feeding calls and other techniques.

By Monday morning, the cow and calf had swum some 40 kilometres to Rio Vista, where they stopped just before a bridge. On Tuesday, crews aboard 26 boats began banging on steel pipes to prompt them to resume their swim to the ocean, but the whales just swam in circles.

The whales are believed to have taken the wrong turn as they participated in the annual humpback migration from the coasts of Baja Mexico to summer feeding grounds off Alaska.