A scientific study says humpback whales in the North Pacific should be looked at as at least five distinct populations, rather than just a single species undergoing recovery.

The study, including genetic analysis, goes against the traditional way humpback whales have been counted as one group in evaluating their recovery as an endangered species.

The study comes at a time when a Hawaii group is petitioning to remove humpback whales in the North Pacific from the endangered species list.

"The North Pacific is a big ocean," said Scott Baker, associate director of the Marine Mammal Institute at Oregon State University and the author of the study.

"Trying to treat this (humpback whales) as one population is not plausible."

Baker, interviewed Thursday, said humpback whales differ based on their geographic distribution, and have genetic differentiations as well. They also frequent their own breeding and feeding areas.

The study was published Wednesday in the journal Marine Ecology — Progress Series and supported by the National Fisheries and Wildlife Foundation, the Office of Naval Research and the Marine Mammal Endowment at Oregon State University.

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

The alliance noted that the number of humpback whales in the North Pacific has steadily grown over several decades.

Alliance President Phil Fernandez said his hui recognizes there are five subgroups of humpback whales.

Fernandez said his organization, including Hawaii fishing and boating clubs, isn’t asking to resume hunting whales, but wants science to be used in fisheries management.

"Let’s not make fisheries management decisions because a fish looks pretty," he said.

Fernandez said that even with a delisting, the federal Marine Mammal Protection Act would continue to make hunting humpback whales illegal.

Scientists estimate there are more than 21,000 humpback whales in the North Pacific, compared with about 1,400 in the mid-1960s.

Baker said scientists are still determining an estimate for the number of humpback whales frequenting Hawaii in the winter but that Hawaii has shown strong evidence of recovery.

Federal whale protection officials say they’re still reviewing Baker’s study and that more than the population of humpback whales has to be considered before removing them from the federal endangered species list.

"There is no magic number," said Allen Tom, regional director of the National Marines Sanctuaries in the Pacific. "You have to look at all factors."

Tom said scientists have to also look at the health of a species and the rate of recovery.

Baker said before considering delisting the humpback whale, scientists need to develop estimates of the five distinct populations.

Humpback whales are found in all oceans of the world.

Baker said the five populations in the North Pacific identified in the study are in water near Okinawa and the Philippines, the western Pacific with unknown breeding grounds, and Hawaii, Mexico and Central America.

Baker said each of the five distinct populations has its own history of exploitation and recovery that would need to be part of an assessment of its status.