Demographic reconstruction of Antarctic fur seals supports the krill surplus hypothesis

• Published in: Genes
• Main Authors: Hoffman, Joseph I., Chen, Rebecca S., Vendrami, David L.J., Paijmans, Anna J., Dasmahapatra, Kanchon K., Forcada, Jaume
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI 2022
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*; Antarctic Fur Seal; Antarctic Fur Seals; Antarctic Krill
• Online Access: http://nora.nerc.ac.uk/id/eprint/532327/; https://nora.nerc.ac.uk/id/eprint/532327/1/genes-13-00541.pdf; https://www.mdpi.com/2073-4425/13/3/541

Much debate surrounds the importance of top-down and bottom-up effects in the Southern Ocean, where the harvesting of over two million whales in the mid twentieth century is thought to have produced a massive surplus of Antarctic krill. This excess of krill may have allowed populations of other predators, such as seals and penguins, to increase, a top-down hypothesis known as the ‘krill surplus hypothesis’. However, a lack of pre-whaling population baselines has made it challenging to investigate historical changes in the abundance of the major krill predators in relation to whaling. Therefore, we used reduced representation sequencing and a coalescent-based maximum composite likelihood approach to reconstruct the recent demographic history of the Antarctic fur seal, a pinniped that was hunted to the brink of extinction by 18th and 19th century sealers. In line with the known history of this species, we found support for a demographic model that included a substantial reduction in population size around the time period of sealing. Furthermore, maximum likelihood estimates from this model suggest that the recovered, post-sealing population at South Georgia may have been around two times larger than the pre-sealing population. Our findings lend support to the krill surplus hypothesis and illustrate the potential of genomic approaches to shed light on long-standing questions in population biology.