In the 1970s two United States laws provided more help for the whales: the Marine Mammal Protection Act and the Endangered Species Act.
By the early 1990s population estimates had shot up to nearly 10,000 humpbacks, and the most recent estimates indicate the numbers have nearly doubled since then.
Starting in 2004, the SPLASH project analyzed 18,000 photographs of whale flukes—or tails—to identify 8,000 individuals.
Cascadia Research in Olympia, Washington, the central coordinator for SPLASH, compared photographs from six known feeding and breeding areas.
By matching whale flukes photographed in their feeding areas with those seen in wintering areas, researchers pinned down individual whale movements and estimated the sizes of various populations.
Despite the overall doubling of humpback whales in the Pacific, estimates of whales wintering in Asia and Central America are still fairly low—a thousand or less.
"Whales along the Asian coast appear to be subject to a high level of incidental mortality," the report authors write.
David Mattila, a NOAA whale researcher and report co-author, explained that Japanese fishermen report a high number of whales entangled in fishing lines along the coast, including mostly minke whales.
"I personally find it very difficult to compare their reporting rates with other Pacific countries, because their fishermen have a 'positive incentive' to report entangled whales," he said.
"That is, if they report and register the DNA, they can keep and sell the whale meat."
(Related: "Japan Courts Poorer Nations in Bid to End Whaling Ban" [April 1, 2008].)
Findings to Come
The SPLASH research will likely yield many more findings in the coming months and years, Mattila said.
As part of their study, researchers took thousands of photographs to determine how scarring from fishing line entanglements and ship strikes vary among regions, which may shed light on threats to whales in the western Pacific.
Teams also collected more than 6,000 tissue samples to study population genetics and levels of pollutants.
These biological samples, which have not yet been analyzed, could provide insight into humpback population structure and reveal threats to the whale's ongoing recovery.
Mattila said he's most fascinated by some of the whales' ambitious—and seemingly unnecessary—migratory patterns.
"Why many U.S. West Coast whales swim almost 2,000 miles [3,220 kilometers] farther than they need to, … going all the way down to Central America and apparently maintaining their genetic uniqueness, is a fascinating question," he said.
"Why would whales apparently migrate through an area where we assume they hear the other whales, but keep going much further south?
"This is also apparently happening along the west coast of southern Africa," he added.
"We need to see the genetics finished to fully understand what is going on there."
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