North Pacific and Alaska Humpback Whale population recovering from near extinction

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.

Humpback breaching

“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 South-west Fisheries Science Centre in La Jolla, California.

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.

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 20th 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 — marshalled 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 make-up in the North Pacific,” the scientists explained.

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 South-east 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.

Back at the lab, teams of scientists underwent an arduous process of matching photos of flukes taken in northern feeding grounds of the Alaska and the Pacific Rim zones to photos of flukes from tropical breeding areas like Hawaii, Baja California and archipelagos south-east of Japan. By analysing how often specific whales were documented in certain areas and at certain times — a photographic version the ecologist’s capture-recapture method — the scientists were able to calculate population sizes.

The initial results were released in 2008, but scientists have since been fine-tuning the data and working to remove sampling biases that might make the estimates less accurate.

“This latest revision to the study provides an accurate estimate for humpback whales in an entire ocean that could not have been possible without researchers working together to pool data,” said co-author John Calambokidis, senior research biologist and co-founder of Cascadia Research.

“While populations of some other whale species remain very low, this shows that humpback whales are among those that have recovered strongly from whaling.”

Alaskan marine icons

With their population recovery, humpbacks have become one of the most common cetaceans seen in the waters off coastal Alaska — an icon of marine life along the South-eastern fiords and frequent summer visitors to Prince William Sound, Cook Inlet and Kenai Fjords areas near Anchorage. After making their annual 3,000-mile migration from Hawaii, these whales prowl near-shore waters and feed on forage fish — startling people with stunning breeches, eerie vocalizations and dramatic dives that bring flukes above the waterline like cetacean flags. The animals live up to 50 years. Large females sometimes reaching 40 tons and more than 50 feet in length.

Here’s an excerpt from the Alaska Wildlife Notebook entry on humpbacks.

Humpbacks are renowned for their various acrobatic displays. One of the more spectacular behaviours is breaching, which researchers believe may be related to courtship or play. During mate selection, groups of 2-20 males can gather around a single female and exhibit a variety of behaviours in order to establish dominance. Breaching, spy-hopping, lob-tailing, tail- slapping, flipper-slapping, charging and parrying can be observed, and these displays can last for hours.

Song is also assumed to have an important role in mate selection; however, scientists remain unsure whether the song is used between males in order to establish identity and dominance, between a male and a female as a mating call, or a mixture of the two. Humpback whale songs are long, complex, and only sung by males. Whales within a distinct population sing the same song; while the songs of whales from other populations are different. A typical song lasts from 10-20 minutes, is repeated for hours at a time, and changes gradually over the years.

Source: AlaskaDispatch, 22nd October 2011


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