Humpback population shows signs of recovery.
Humpback whale numbers in the northern Pacific Ocean have ballooned to nearly 20,000, the largest population seen since the majestic mammals were hunted nearly to extinction half a century ago.
The number of humpbacks hit an all-time low of 1,400 or even lower by 1966, when their hunting was banned internationally. The new census, from one of the largest whale studies ever undertaken, shows that the animals have rebounded much better than expected.
“We had no idea the population could have grown this high,” says John Calambokidis, a biologist at Cascadia Research Collective, a non-profit environmental research institute in Olympia, Washington, and a principal investigator on the study.
But cetologists are concerned about the estimated 900 humpbacks that migrate to the western Pacific. This subpopulation may be being hunted illegally, with some getting entangled in the nets of fishermen. Still, researchers say that the western Pacific population is increasing at more than 6% per year — roughly the same rate as humpbacks in other regions.
The three-year study, called SPLASH (Structure of Populations, Levels of Abundance and Status of Humpbacks), involved more than 400 researchers from 10 nations. Its US$3.7-million price tag was paid for with funding from the US National Oceanic and Atmospheric Administration (NOAA), the Canadian government and private sources. It used everything from ocean-going research ships to motorized outrigger canoes to identify whales by their fluke markings, then monitor them from their feeding grounds off Canada and the Aleutian Islands to their winter and breeding grounds off Hawaii, Latin America and Asia.
“This is a great candidate to show the success of conservation programmes,” says Jay Barlow, a marine mammalogist with the NOAA Southwest Fisheries Science Center in La Jolla, California, and a study leader. The project was conceived in 2002 when US laws such as the Endangered Species Act and the Marine Mammal Protection Act were under attack by Republicans in Congress.
The report's findings may open a new dialogue about the study and regulation of humpbacks under the auspices of the International Whaling Commission. And there will probably be talks about re-evaluating the humpback's current classification as endangered.
Barlow says that revising the protection status to 'threatened' may be reasonable for the eastern-Pacific population, but that western-Pacific whales should remain listed as 'endangered'. “This study will open a discussion, which will be a long one,” he says.
Japan continues 'scientific whaling' attempts on a separate population of humpbacks in the southern Pacific. Last year, the country had planned to kill nearly 1,000 humpback, fin and minke whales in the area, but international pressure reduced the take to about 550 minkes.
SPLASH also intends to furnish details about the humpback population structure, including the animals' loyalty to certain feeding or breeding regions and how this affects their survival.
Almost 8,000 humpbacks were individually catalogued, with tissue samples taken from more than 6,000 of these for DNA analysis. Already, SPLASH has revealed the existence of an unknown wintering and breeding ground — a refuge that researchers haven't yet located, but is probably in the middle of the Pacific Ocean. DNA records may play an important part in locating the area. “Finding that will be a fun project,” says Barlow.
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Dalton, R. Whales are on the rise. Nature 453, 433 (2008). https://doi.org/10.1038/453433a