As everyone knows, whale populations suffered a pretty thorough shellacking at the hands of the commercial whaling industry. Some of those populations, such as bowhead whales off Spitsbergen or in the Okhotsk Sea, or right whales in the North Pacific, are still showing very little, if any, sign of recovery. Others, such as gray whales in the western North Pacific and right whales in the North Atlantic, remain in grave danger of extirpation, their whaling-induced declines compounded by, for example, entanglement in fishing gear or collisions with shipping.
Others, however, seem to be reaping the benefit of decades of protection. Right whales off South Africa, eastern South America and Australia have been recovering for years, and by some estimates the gray whales of the eastern North Pacific – the ones that swim along the US west coast – now number the same as they did before whalers found them.
(The International Whaling Commission publishes recent estimates of population numbers and status here and here.)
Now researchers say another example can be added to the "doing fine" list. According to a recent article in Marine Mammal Science, there are at least 21,000 humpback whales in the North Pacific, 15 times greater than the 1,400 believed to exist mid-century, and possibly more than in the years before whaling. The findings were the result of the Structure of Populations, Levels of Abundance and Status of Humpbacks (or SPLASH) study, one of the largest international collaborative studies of any whale population ever conducted. Over the course of three years, more than 400 scientists from 10 different countries photographed humpback whales in the North Pacific, cataloging their unique fluke patterns, and used darts to take genetic samples. Then for fully three years afterward, they analyzed, crunched, and refined the data they collected, until reaching their final figure.
The most recent previous estimate of the North Pacific humpback population, based on research conducted from 1990 to 1993, yielded a figure of approximately 8,000. That suggests the population is increasing by a little over 8 percent a year, and although no other estimates have been conducted for the population as a whole, the paper's authors write that that figure is consistent with figures that other researchers have produced for humpbacks in part of that range.
The overall total is almost certainly an underestimate, the authors note, partly because, although researchers studied humpbacks in summer feeding and winter breeding areas, the location of some of those wintering areas remains unknown, and so the whales therein evaded detection.
"This latest revision to the study provides an accurate estimate for humpback whales in an entire ocean that could not have been possible without researchers working together to pool data," said study co-author John Calambokidis of Cascadia Research in a press release. "While populations of some other whale species remain very low this shows that humpback whales are among those that have recovered strongly from whaling."
IMAGE: Humpback whale breaching. (NOAA)