NELSON: Conservationists in New Zealand were struggling Saturday to save 18 long-finned pilot whales after a mass stranding in which seven of the animals died.

The surviving whales had been refloated but appeared to lack the energy to swim away, the Conservation Department's area manager John Mason said.

The whales, which beached themselves on Friday afternoon at the top of New Zealand's South Island were from a pod of about 70 that appeared at Golden Bay, where strandings are common.

Two months ago, 47 pilot whales died after being stranded on tidal flats in the area near the tourist city of Nelson.

Pilot whales up to six metreslong are the most common species of whale seen in New Zealand waters.