The first humpback whale of the Hawaii migration season has been observed in waters off Kauai.

Holo Holo Charters, which offers whale- and dolphin-watching tours, spotted the adult humpback a mile off Kekaha Sugar Mill in west Kauai on Monday.

"It was a great surprise. It’s a pretty early sighting," said Chandra Bertsch, Holo Holo Charters’ general manager. "It definitely shows signs of a good whale season to come."

Large numbers of the endangered species are usually seen between December and May when they migrate from Alaska to the warm waters of Hawaii, where calving occurs.

Early visits have been recorded recently, including one on Aug. 30 in 2012.

Humpback whale numbers in Hawaiian waters have increased from an estimated 1,000 in 1979 to between 10,000 and 12,000 in recent years.

The Hawaiian Islands Humpback Whale National Marine Sanctuary was designated by Congress in 1992, covering some 1,370 square miles of federal and state waters.

Rules have been implemented to protect humpback whales, including one requiring vessels to maintain a distance of 100 yards from a humpback in sanctuary waters.

The Hawaii Fisherman’s Alliance for Conservation and Tradition Inc. filed a petition in April 2013 seeking to remove humpbacks in the North Pacific from the federal endangered species list.

And Alaska officials are seeking the delisting for the Central North Pacific stock that spends winters in Hawaii and summers foraging off Alaska and northern British Columbia.

Alaska officials have argued the total numbers are higher than the 15,000 that existed at the onset of modern whaling before 1905.

Officials said the number in the North Pacific, including those that migrate to areas other than Hawaii, is about 21,800.

Some scientists have argued the humpbacks in the North Pacific should be looked at as five separate groups, rather than just a single species undergoing recovery.

The Alaska petition was filed with the National Marine Fisheries Service in February.

The federal agency has determined the petitions from the Hawaii group and Alaska may be warranted and federal officials are continuing to review the petitions.

Federal officials note even if humpback whales are taken off the endangered species list, they are still protected under the Marine Mammal Protection Act.

The humpback whale was listed as an endangered species in 1970 under the Endangered Species and Conservation Act of 1969.