A whale of a tale in the North Pacific

Five distinct humpback whale populations have been
identified in the North Pacific clearing the way for these great mammals to be
designated as distinct populations segment by the International Union for the
Conservation of Nature (IUCN). The study is an internationally collaborative effort
including United States, Japan, Russia, Mexico, Canada, the Philippines, Costa Rica,
Panama, Nicaragua and Guatemala under the byline SPLASH (Structure of Populations,
Levels of Abundance and Status of Humpbacks).

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Led by Scott Baker, associate director at the Marine Mammal
Institute at Oregon State University’s Hatfield Marine Science Center the team
examined nearly 2,200 tissue biopsy samples collected from humpback whales in
10 feeding regions and eight winter breeding regions during a three-year
international study.

They used sequences of maternally inherited
mitochondrial DNA and “microsatellite genotypes,” or DNA profiles, to
both describe the genetic differences and outline migratory connections between
both breeding and feeding grounds.

“Though humpback whales are found in all oceans of the
world, the North Pacific humpback whales should probably be considered a
sub-species at an ocean-basin level — based on genetic isolation of these
populations on an evolutionary time scale,” says Baker.

“Within this North Pacific sub-species, however,
our results support the recognition of multiple distinct populations,”
Baker added. “They differ based on geographic distribution and with
genetic differentiations as well, and they have strong fidelity to their own
breeding and feeding areas.”

While humpback whales are listed as endangered in the
United States under the Endangered Species Act, they have been downlisted by
the IUCN globally. However, the IUCN recently added two population segments as
endangered: one in the Sea of Arabia, and the other in Oceania.  Baker says this sets a precedent for the
newly identified populations in the North Pacific to be listed as endangered
too.

How management authorities respond to the study
identifying the distinct populations remains to be seen, Baker said, but the
situation “underscores the complexity of studying and managing marine
mammals on a global scale.”

The five populations identified in the study are:
Okinawa and the Philippines; a second West Pacific population with unknown
breeding grounds; Hawaii, Mexico and Central America.

Results of the study are being published this week in
the journal Marine Ecology — Progress Series. It was supported by the National
Fisheries and Wildlife Foundation, the Office of Naval Research, and the Marine
Mammal Endowment at OSU.

Read more at EurekAlert
and Oregon State
University Cetacean Conservation Genetics Lab
.

Whale
tail
image via Shutterstock.

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