Humpback whales of the North Pacific and Alaska have rebounded dramatically from near extinction half a century ago and now number at least 21,000 animals, according to the most comprehensive count of the species ever undertaken.

“Results confirm that the overall humpback whale population in the North Pacific has continued to increase and is now greater than some prior estimates of pre-whaling abundance,” wrote the 19 co-authors from Alaska, British Columbia, Washington, Oregon, California, Mexico and Japan in a paper published this week in the journal of Marine Mammal Science.

This updated population figure is about 15 times greater than the 1,400 whales thought to remain alive in the region after the species was decimated by mid-century industrial whaling, and at least 1,000 more animals than the biologists estimated in 2008.

"We feel the numbers may even be larger since there have been across-the-board increases in known population areas and unknown areas have probably seen the same increase,” said Jay Barlow, the lead author and a marine mammal biologist with the Southwest Fisheries Science Center in La Jolla, Calif.

Humpback whales have been listed as endangered by the United States for decades, but populations throughout the world have increased since whaling was banned in 1966. NOAA Fisheries announced in 2009  it would review the status of the species’ listing under the Endangered Species Act.

"These improved numbers are encouraging," Barlow added in this NOAA Fisheries story.

Back from the brink

Before commercial whaling, as many as 125,000 humpbacks swam the world’s oceans, divided into the broad populations in the North Pacific, the North Atlantic and Southern oceans. Decades of industrial style whaling in the middle of the 20^th century wiped out 90 percent of the population to about 5,000 worldwide by 1966, including the 1,400 animals in the North Pacific, according to this genetic study

Once whaling ended, the species began to rebound. This updated humpback estimate comes from one of the most ambitious whale population studies ever undertaken. The SPLASH study — the Structure of Populations, Levels of Abundance and Status of Humpbacks — marshaled more than 400 scientists from 50 research groups in 10 countries to seek out humpback whales in every known summer feeding and winter breeding grounds in the entire North Pacific basin.

“The SPLASH research was a three-year project … involving NOAA scientists and hundreds of other researchers from the United States, Japan, Russia, Mexico, Canada, the Philippines, Costa Rica, Panama, Nicaragua and Guatemala and was the first systematic survey ever attempted to determine the humpback whales' overall population, structure, and genetic makeup in the North Pacific,” the scientists explained here.

During three winters and two summers between 2004 and 2006, observers ventured out in small boats and some ships in 11 specific regions to scan horizons for blows and then approach the 40-ton behemoths in waters from Baja California to rainy Southeast Alaska, from Maui to Prince William Sound, from the Ogasawara Islands (location of Iwo Jima) to the Bering Sea.

Over the course of 27,000 encounters with humpbacks, the scientists collectively snapped 18,469 quality photographs of whale flukes, whose unique markings, pigments, scars and shapes shape can be used as a sort of “fingerprint” to identify individual whales. They also took 6,178 tissue samples for genetic testing.