A group of blue whales that frequent the South Taranaki Bight between the North and South islands of New Zealand appears to be part of a local population that is genetically distinct from other blue whales in the Pacific Ocean and Southern Ocean, a new study has found.
Hydrophones deployed in the region recorded blue whale calls on 99.7 percent of the days between January and December in 2016.
“There is no doubt that New Zealand blue whales are genetically distinct, but we’re still not certain about how many of them there are,” researcher Dawn Barlow commented. “We have generated a minimum abundance estimate of 718, and we also were able to document eight individuals that we re-sighted in multiple years in New Zealand waters, including one whale seen in three of the four years with a different calf each time, and many others we saw at least once.”
The study, led by Oregon State University’s Marine Mammal Institute, is important because the South Taranaki Bight has several oil and gas extraction rigs and the New Zealand government recently issued its first permit for mining the seafloor there for iron sands. Churning up the sand could muddy the sea and disrupt the natural food chain. The sand will be sucked up to a floating production vessel, the valuable iron content removed and shipped away for further processing while the sandy remains are pumped back to the seabed.
The blue whales found off New Zealand are not quite as large as Antarctic blue whales, which scientists believe to be the largest animals to have ever lived on Earth. Antarctic blues, when they reach adulthood, can range from 28 to 30 meters in length (nearly 100 feet). The other blue whales, though slightly smaller, are still formidable at about 22 meters in length (or 72 feet).
Documentation of a New Zealand blue whale population based on multiple lines of evidence, Barlow et al. Endangered Species Research 36:27