Anthropogenic factors inhibit the lengthy recovery of the blue whale populations. Blue whale populations are slowly increasing however low population densities influenced by anthropogenic factors pose an impending threat towards the genetic diversity of the blue whale populations and the conditions they are forced to survive in.
Genetic Diversity
Genetic bottleneck is described as the dramatic reduction in population size, usually resulting in genetic drift - a shift in the genetic composition of a species. The elimination of 99 percent of the blue whale species during the commercial whaling period inevitably resulted in a genetic bottleneck which severely reduced the genetic diversity of the blue whale populations. Forty-six years after the prohibition of the hunting of blue whales, mitochondrial DNA surveys conducted on blue whale species have indicated a high level of diversity among populations of 2000, providing hope that the restoration of the species is slowly beginning to occur.
Although populations are slowly increasing, low population densities influenced by anthropogenic factors pose an impending threat towards the genetic diversity of the blue whale populations. Furthermore, blue whales have a low reproductive output, producing only one offspring every 1-2 years. Any more threats to the survival and replenishment of the blue whale species poses the risk on the genetic diversity of the species. Large numbers of individuals would no longer be able to reproduce and therefore contribute to genetic diversity.
Past and Current Conditions
Despite its categorization as an endangered species with subspecies like the Antarctic blue whale identified as Critically Endangered, the blue whale is showing positive indications of restoration Currently it has an increasing population trend, that may be due in large part to the moratorium on commercial whale hunting, which significantly protected the species.
In previous evolution and surviving conditions (prior to commercial whaling) the blue whale was able to survive without many threats from other marine organisms and humans. This is due in large part to its large size and relatively speedy swimming abilities. Furthermore the effects of climate change were not as prevalent as they are today. With cooler water temperatures, there was an abundance in krill population for consumption.
Blue whales in the oceans of the Southern Hemisphere were estimated to have thrived and evolved in a population size of 200 000, before commercial whaling. Currently at an alarmingly low population size, the species once again is no longer threatened by whaling and is slowly increasing at a trend of 8 percent a year. Also heavily exploited in the North Atlantic, trends have indicated slow but present increase in population size. However, it should be noted that blue whales remain rare in the Northeastern Atlantic ares, in which they had previously been abundant. In the North Pacific, increasing population trends of blue whales occur mainly in the Gulf of California, which demonstrates a promising growth of 3 percent a year.
Although these trends indicate that the recovery of the blue whale is possible and its critical population size reversible, the species remains under threat of anthropogenic change which negatively impacts the evolution of the species. During the whaling period the blue whale came under threat of extinction with dramatic reductions in populations. Currently the species is under threat of behavioural changes due to the habitat degradation and human activity complicating its proper survival.
