The first comprehensive genetic study of humpback whale populations in the North Pacific Ocean has identified five distinct populations — at the same time a proposal to designate North Pacific humpbacks as a single “distinct population segment” is being considered under the Endangered Species Act.
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 Oregon State University.
The scientists 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, known as SPLASH (Structure of Populations, Levels of Abundance and Status of Humpbacks). 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,” said Scott Baker, associate director of the Marine Mammal Institute at Oregon State University’s Hatfield Marine Science Center and lead author on the paper.
“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.”