Southern right whales are cherished members of the right whales (Eubalaena) genus of baleen whales which comprises only three species.They call Australian waters home, and we owe it to them to ensure they never come so close to extinction and exploitation as they once did.
Southern right whales underwent a dramatic and prolonged demographic bottleneck due to whaling, with the counts dropping from a healthy population of ~100,000 whales in the Southern Hemisphere in the late 1700’s to under 400 whales in 1920’s (1). Because of their enormous blubber reserves, curious nature and preferred calving grounds close to the southern Australian coastlines they were extremely popular as a whaling target, to the extent that whalers would often refer to them as the “right whale to hunt” (1). The nickname has stayed with the animals.
Thanks to international protection from whaling, the species has recovered in some parts of its former range (2). Currently, sightings vary from large aggregations, seen in key winter calving/nursery areas (South Africa, Australia, Argentina, Brazil, sub-Antarctic New Zealand), to regular sightings of small numbers of SRWs in other parts of the historical range (e.g., southeast Australia, mainland New Zealand) (3).
The whales weigh up to 80,000 kilograms and measure 16-18 meters in length (4). They can live up to 80 years, and start reproducing at 7-9 years of age, based on repeated sightings of photo-identified individuals. Females mate with multiple males, and will have only one calf every 3-5 years.
The whales have a form of 'migratory culture' whereby they learn their mothers' preferred migratory destinations in their first year of life. They stay relatively true to these migratory traditions, and it's a factor that shapes their genetic population structure (5, 6).
The location of the offshore foraging grounds of southern right whales are not well understood, and much effort is currently being invested to characterise where the whales are feeding using technology such as satellite tracking (e.g., some tracked New Zealand southern right whales are currently feed just off Western Australia). A place of interest in this respect is the subantarctic island of South Georgia. It is a biodiversity hotspot and an accessible foraging ground for southern right whales. Recent work by the British Antarctic Survey has focused on the recovery of whales from whaling in this ecosystem.
To support ongoing conservation efforts DNA Zoo has been working with Dr. Emma Carroll, School of Biological Sciences, University of Auckland, and Dr. Jennifer Jackson at the British Antarctic Survey to get a chromosome-length genome assembly for the species. For the purpose, a southern right whale sample was collected from South Georgia using funding from EU BEST, DARWIN PLUS, South Georgia Heritage Trust, Friends of South Georgia Island, WWF and logistical support from the Government of South Georgia and the South Sandwich Islands (permit RAP 2017-017). Samples were collected as part of the Ecosystems component of the British Antarctic Survey Polar Science for Planet Earth Programme, funded by The Natural Environment Research Council. Additional acknowledgement to researchers Amy Kennedy, Matt Leslie, Artur Andriolo, Susie Calderan, Russell Leaper and Emilie Stepien, and the Song of the Whale crew and Marine Conservation Research International for vessel charter support.
We gratefully acknowledge the collaboration, samples from Argentina and the draft assembly provided by Mark Yandell's lab at University of Utah with contributions from Michael S. Campbell, Brian Dalley, Edgar J. Hernandez, Barry Moore, Andrea Chirife, Matias Di Martino, Mariano Sironi, Luciano O. Valenzuela, Marcela Uhart, Victoria J. Rowntree, Guy D. Eroh, Sancy A. Leachman and Jon Seger. Construction of the SRW draft assembly was funded and supported by the Illumina Corporation, by the H.A. and Edna Benning Fund, and by the US National Science Foundation.
The Hi-C work was supported by resources provided by DNA Zoo Australia, The University of Western Australia (UWA), DNA Zoo at Aiden Lab at Baylor College of Medicine with additional computational resources and support from the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia.
Today we share the resulting genome assembly. Check out the 21 chromosomes below!
The assembly will facilitate ongoing conservation efforts. In particular we hope it will help with the development of a genotyping panel to help understand the kin relationships of the whales, which in turn, will tell us about their abundance and recovery. This is the work that Dr. Emma Carroll and team of collaborators are doing on New Zealand southern right whales at the University of Auckland.
Once the pandemic is over, come meet these beautiful whales at their nursery grounds located in Augusta in Western Australia during mid-July to late August!
The following people contributed to the Hi-C chromosome-length upgrade of the project: Erez Aiden, Olga Dudchenko, David Weisz, Ashling Charles & Parwinder Kaur.
Citations
1. Jackson, J. A., Patenaude, N. J., Carroll, E. L. & Baker, C. S. How few whales were there after whaling? Inference from contemporary mtDNA diversity. Mol. Ecol. 17, 236–251 (2008).
2. Bannister, J. L. Population trend in right whales off southern Australia 1993–2010. Unpubl. Rep. Present. to Int. Whal. Comm. Work. South. right whales, 13–16 Sept. 2011, Buenos Aires, Argentina (2011). Available at: https://iwc.int/home
3. Carroll, E. L. et al. Population structure and individual movement of southern right whales around New Zealand and Australia. Mar. Ecol. Prog. Ser. 432, 257–268 (2011).
4. Vashchenko YV, Clapham PJ. "Pushed to the Edge: Soviet Catches of Right Whales in the Eastern North Pacific". Alaska Fisheries Science Center Quarterly Research Reports (2011).
5. Carroll, E. L. et al. Cultural traditions across a migratory network shape the genetic structure of southern right whales around Australia and New Zealand. Nature Scientific Reports. 5, 16182 (2015).
6. Valenzuela LO, Sironi M, Rowntree VJ, Seger J. Isotopic and genetic evidence for culturally inherited site fidelity to feeding grounds in southern right whales (Eubalaena australis). Mol. Ecol. 18,782-791 (2009).
7. Carroll, E.L. et al. Genetic diversity and connectivity of southern right whales (Eubalaena australis) found in the Brazil and Chile-Peru wintering grounds and the South Georgia (Islas Georgias del Sur) feeding ground. Journal of Heredity. 111, 263-276 (2020).