Large sea otter populations once ranged from Northern Japan all the way around the Northern Pacific Rim to Baja California. However, in 1741 when the fur trade began, their numbers started to rapidly decline. The pelts of sea otters were so in demand that sea otter populations were driven to near extinction by the end of the 19th century. In 1911 sea otters were protected by the International Fur Seal Treaty but for some populations this was already too late.
In the Kuril Islands, Kamchatka Peninsula, Aleutian Islands, South-Central Alaska and California the small remaining populations began to grow. Some populations have returned to their historical population sizes but others, such as the population in California, have grown more slowly. Annabel Beichman, a PhD student at UCLA, together with Monterey Bay Aquarium are leading the effort to aid the recovery of the sea otters. They plan the first ever sequencing of the sea otter genome.
The extreme decline, to a very small size, in the sea otter population followed by the re-expansion has led to what is known as a population or genetic bottleneck. The lucky survivors that emerged on the other side of the bottleneck will pass on their genetic information to all future populations. This bottleneck can have long-lasting genetic consequences with loss of genetic diversity in the population leading to accumulation of harmful genetic mutations. These mutations could impact an individuals’ ability to withstand disease, reproduce or survive to adulthood.
The researchers are in the process of sequencing the first ever sea otter genome using a blood sample taken from an otter resident at the Monterey Bay Aquarium. They also plan to sequence the genomes of 10 other sea otters taken from each of the six remaining populations as well as sequencing some ancient sea otter DNA from before the bottleneck.
This genetic information will be incorporated into sea otter conservation plans. It is hoped that this information will allow researchers to identify which populations are more vulnerable to disease or catastrophe due to small population sizes and to determine if populations could benefit from introduction of animals with different genetic profiles to increase genetic diversity.
Sea otters are a keystone species playing a critical role in the health of coastal ecosystems so this project is vital to restoring this balance.
- Vickie Flint PhD
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