Conservationists struggled on Friday to keep about 45 whales from beaching themselves on a remote island in southern New Zealand.

Their efforts over a period of 30 hours appear to have been rewarded as the whales swam for open water Friday night. But a flight was planned for Saturday at dawn to make sure the animals don't turn around and head for shore.

On Thursday, 22 pilot whales died after beaching themselves at Maori Beach on Stewart Island, located 35 kilometres south of New Zealand's South Island.

Dozens of conservationists rushed to the beach after the whales were spotted late Thursday.

About 40 of the animals were taken back out to sea by the high tide Friday morning, and the effort to keep them away began.

Meanwhile, the carcasses of the 22 dead whales, each weighing about a tonne will be left to rot on the remote beach.

A Conservation Department spokesman said the location of the beach makes burying the whales, or otherwise disposing of them, impossible.

Two years ago, about 288 whales died after beaching themselves on another beach on Stewart Island, the southern-most island in New Zealand.