An estimated 500 volunteer whale watchers at 59 sites gathered data along the shores of O'ahu, Kaua'i, the Big Island and Kaho'olawe yesterday for the annual Hawaiian Islands Humpback Whale National Marine Sanctuary Ocean Count.

Observers sighted approximately three whales per 15-minute segment at each location, with the exception of Kaho'olawe, which reported around 10 whale sightings during every 15-minute segment at the island's one observer location.

Hawaiian waters are a critical breeding habitat for about two-thirds of the North Pacific stock of humpback whales.

The whales migrate each winter to their Hawaiian habitat to mate, calve and nurse their young. The sanctuary is managed by the National Oceanic and Atmospheric Administration.