Most populations of humpback whales are no longer on the United States endangered species list thanks to international conservation efforts, the National Oceanic and Atmospheric Administration announced Tuesday.

Four decades of national and international initiatives to protect and conserve the marine mammals have helped nine of 14 humpback population segments rebound from historically low levels.

"Today's news is a true ecological success story," said Eileen Sobeck, assistant NOAA administrator for fisheries.

"Whales, including the humpback, serve an important role in our marine environment. Separately managing humpback whale populations that are largely independent of each other allows us to tailor conservation approaches for each population."

After commercial whaling severely reduced populations, the US listed all humpback whales as endangered in 1970. Today, just four whale groups remain on that list, and one is now listed as threatened.

The International Whaling Commission's whaling moratorium imposed in 1982 -- which remains in effect -- played a crucial part in the comeback, NOAA said.

The US Marine Mammal Protection Act that protects marine mammals within US waters still applies to all humpback whales, regardless of endangered status.

The MMPA prohibits the killing of certain marine mammals in US waters and by US citizens on the high seas, and bans their importation into the United States.

Two separate regulatory decisions filed Tuesday maintain protection for whales living off Hawaii and Alaska by "specifying distance limits for approaching vessels."

Two of the four humpback groups still considered endangered can be found in US waters at some times of the year.

The Central American population looks for food in the Pacific Ocean off the US West Coast, while the group in the Pacific Northwest spends time in the Bering Sea and near the Aleutian Islands.

The humpback group from Mexico now listed as threatened regularly goes to the West Coast of the continental United States and Alaska.

In 2010, NOAA launched an extensive review of the status of humpback whales that resulted in the reclassification of the species into 14 distinct populations.

NOAA proposed last year to remove 10 of those 14 groups off the endangered list and gave the public 90 days to comment on the proposed change before finalizing its decision.

Humpback whales can grow to 60 feet (18 meters) and live 50 years. They weigh up to 40 tons and eat tiny crustaceans called krill, often as much as 3,000 pounds (1,360 kilograms) per day.

The NOAA announcement follows US President Barack Obama's establishment of the world's largest marine reserve, home to thousands of rare sea creatures in the northwestern Hawaiian islands.