Saved from whaling, blue whales now face threat from global warming, human activities: Study

NEW DELHI: Blue whales, the largest living animals, have recovered from being hunted, only to face the growing challenges from global warming and other human threats like underwater noise, pollution and disrupted food sources, according to a new stocktake of their population.
Researchers found the greatest genetic differences among the blue whale populations in the eastern Pacific, Antarctic subspecies and the pygmy subspecies of the eastern Indian and western Pacific.Blue whales average about 27 metres in length.
Natural selection could be one of the reasons behind these differences, they said.
“Each of these groups need to be conserved to maintain biodiversity in the species, and there are indications that natural selection in different environments contributed to driving genetic differences between the high-level groups,” said Catherine Attard, College of Science and Engineering, Flinders University, Australia. He is the first author of the study published in the journal Animal Conservation.
Using genomic analysis, the researchers found an “unexpected” similarity between the blue whales of the eastern South Pacific and those of the eastern North Pacific, suggesting they were part of the same subspecies, and not separate as they are currently considered.
“Unexpected” because the mammals are thought to have opposite when their populations exist on the either side of the equator, they said.
Further, despite low genetic diversity between the eastern Indian and western Pacific populations, the researchers identified the eastern Indian Ocean, western South Pacific Ocean and potentially western Indian Ocean as “different” populations within the Indo-western Pacific.
The team found no evidence of inbreeding, and described it as “good news” for the potential recovery of subspecies and populations. Challenges still, however, remain, they said.
The recovery of baleen whales — of which the endangered blue whales is a type –is now threatened by multiple human sources, the team explained.
These sources included underwater noise, changing availability of food driven by human-induced effects on ocean productivity, environmental contaminants, ship collision and entanglement in fishing gear, they said.
While blue whales became protected from commercial whaling in 1966, the International Whaling Commission (IWC) implemented a global moratorium 20 years later.
“Our findings build on decades of work to improve the management of endangered blue whales under the International Whaling Commission,” said Attard.
The researchers called on the IWC to use their findings to refine their classification of blue whales for conservation and management purposes.
Along with generating the largest global genomic dataset to date for blue whales, the researchers linked the genetic results to blue whale calls and typical migratory and breeding patterns, using satellite tagging and acoustics.
Genomics is vital to and unparalleled in power in determining population differences, connections and other characteristics important to informing biodiversity conservation, said another study co-author Luciano Beheregaray from Flinders University.