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).
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.