Good news from off the coast of California in the United States: once ravaged by whaling, the California blue whale population has rebounded to 97 percent of historic levels.
Researchers from the University of Washington had to get creative to prove this promising upswing. Before whaling was banned in 1966, most of the hunting in the Pacific Ocean where these whales reside, was carried out by Russian fleets. As such, much of the data surrounding their catches was kept secret under Soviet rule. Even once they had gained access to these documents, the scientists were still unable to calculate accurate historic populations.
Pacific blue whales are categorized as two distinct populations: California blue whales, and those that live off the coasts of Japan and Russia. To distinguish between the two populations, the researchers studied the songs the two groups used to communicate. Learning the different tunes allowed research teams to demarcate a boundary between the two populations that was then compared to data from Soviet records. Once the research team was able to accurately calculate the numbers of each population lost to whaling, they were then able to establish a historic population size, against which the sizeable California rebound was measured.
While the California blue whales are no longer threatened by whaling, they are still vulnerable to modern society. In an effort to protect the whales from fatal ship strikes, of which there are on average 11 per year, Californian authorities have taken to paying merchant ships to slow their speeds off of the coast. These ongoing conservation efforts hope to support the blue whales’ return to carrying capacity in the Pacific Ocean.
Cole Monnahan, a researcher and lead author on the resulting paper, recognized the human influence on the whales’ rebound, saying, “California blue whales are recovering because we took actions to stop catches and start monitoring. If we hadn’t, the population might have been pushed to near extinction—an unfortunate fate suffered by other blue whale populations.” One such population is the Antarctic blue whale. At a frighteningly low one percent of their historic numbers, drastic solutions are needed to protect the survival of this dwindling population.