Five Distinct Humpback Whale Populations Identified In North Pacific Ocean
December 4, 2013

Five Distinct Humpback Whale Populations Identified In North Pacific Ocean

Lee Rannals for – Your Universe Online

A new genetic study shows there are five distinct humpback whale populations in the North Pacific Ocean.

There is currently a proposal to try and designate North Pacific humpbacks as a single distinct population segment, which could ultimately threaten the species’ endangered status.

Humpback whales are listed as endangered in the US under the Endangered Species Act, but the species has recently been downlisted by the International Union for the Conservation of Nature (IUCN) on a global level. Two population segments recently were added as endangered by the IUCN and it is likely one or more of the newly identified populations may be considered endangered. Categorizing the new whale populations into one distinct population segment could mean that some of the whales could go on unprotected.

The latest study, published in the journal Marine Ecology — Progress Series, involved examining nearly 2,200 tissue biopsy samples collected from humpback whales in 10 feeding regions and eight winter breeding regions during a three-year study. The team used sequences of maternally inherited mitochondrial DNA and “micro satellite genotypes.”

"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," Scott Baker, associate director of the Marine Mammal Institute at Oregon State University's Hatfield Marine Science Center and lead author on the paper, said in a press release.

He said that within this North Pacific sub-species, the team’s results support the recognition of multiple distinct populations.

"They differ based on geographic distribution and with genetic differentiations as well, and they have strong fidelity to their own breeding and feeding areas,” Baker said in the release.

He said that how management authorities respond to the study identifying the distinct North Pacific humpback populations remains to be seen. However, he added the situation “underscores the complexity of studying and managing marine mammals on a global scale.”

The international study, known as Structure of Populations, Levels of Abundance and Status of Humpbacks (SPLASH), used photo identification records to estimate humpback whale populations. The team estimated there are about 22,000 humpbacks throughout the North Pacific. The recovery strategies for these whales have been successful on a broad scale, but the team says those numbers are variable among different populations.

"Each of the five distinct populations has its own history of exploitation and recovery that would need to be part of an assessment of its status," said Baker, who is a professor of fisheries and wildlife at OSU. "Unlike most terrestrial species, populations of whales within oceans are not isolated by geographic barriers. Instead, migration routes, feeding grounds and breeding areas are thought to be passed down from mother to calf, persisting throughout a lifetime and from one generation to the next.”

The researchers believe the fidelity to migratory destinations is cultural, not genetic, and it is this culture that isolates whales and leads to genetic differentiation.