A new genomic study by UCLA biologists shows that whaling in the 20th century destroyed 99% of the Eastern North Pacific fin whale breeding, or "effective," population -- 29% more than previously thought. But there is also some good news: Genes among members of this endangered species are still diverse enough that current conservation measures should be be enough to help the population rebound without becoming inbred. The study also found that the health of this group is essential for the survival of highly isolated, genetically distinct fin whales in the Gulf of California.
The study, published in Nature Communications, is among the first to use whole genome information to get a picture of the size and genetic diversity of today's population. Previous studies had to rely on whaling records or mitochondrial DNA, which is inherited only from the mother, providing limited genetic information. The genome analyses revealed that the Gulf of California population diverged around 16,000 years ago, with a population that hovered around 114 adults of reproductive age. The population of breeding adults is a key indicator of a species' ability to sustain itself. The Eastern North Pacific effective population remained at around 24,000 individuals for thousands of years, until a severe decline happened between 26 and 52 years ago -- a period that coincides with 20th century whaling -- to only about 305 individuals.
Luckily, thanks to the slow pace of fin whale reproduction, the population reduction caused by whaling at its strongest point lasted for only two fin whale generations -- a 50-year span -- and ended with the implementation of the international whaling moratorium in 1985. Since then, the population has slowly recovered, and harmful genes have not had time to pile up. The future of fin whales in the Gulf of California also depends on the recovery of the Eastern North Pacific population. The genomic analysis showed that many harmful genes have become common in the former group, and that the only source of new genetic variants is the occasional Eastern North Pacific whale who wanders into their territory about once in every three generations. This infusion of new genetic material, however, has been enough to keep the population going.
