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Genomic evaluation of Australian sub-adult white sharks Carcharodon carcharias reveals kin aggregation with low population size
Journal article   Peer reviewed

Genomic evaluation of Australian sub-adult white sharks Carcharodon carcharias reveals kin aggregation with low population size

Dean Blower, Zach Clark, Jessica Fish, Adam Miller, Craig Sherman, Andrew Weeks and Paul Butcher
Marine Ecology Progress Series, Vol.First online
07/2025
DOI: https://doi.org/10.3354/meps14926
Appears in  Recent Faculty of Science and Engineering Publications

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Abstract

Conserving ecologically important species, such as large marine predators, requires regular and accurate population assessments. We evaluated the genetic and demographic status of eastern Australian sub-adult white sharks Carcharodon carcharias, revealing that they remain at critically low numbers and exhibit unsuspected degrees of sibship. Genetic analyses of over 500 individuals using nearly 5000 SNP loci revealed 100 family clusters comprising 314 full-sibling and 701 half-sibling pairs. Morphometric ageing showed strong correspondence between birth year and full-sibling relationships, indicating at least 95 distinct fullsib litters, suggesting long-term kin aggregation is maintained across broad spatial and temporal scales. Further genetic analyses indicated low effective population size (Ne = 276) and small numbers of effective breeders over 7 consecutive years (harmonic mean Nb = 100, 2011-2017), signifying limited genetic diversity and constrained population growth. Demographic modelling, incorporating species-specific life history and multiple- versus single-paternity breeding (MPB vs. SPB), produced low estimates of total population size (N) and adult population size (Nc), consistent with prior studies. Although the prevalence of MPB in this population remains uncertain, models suggest MPB could maintain higher effective size with fewer C. carcharias adults than SPB. Together, this evidence for substantial sibship, low genetic diversity, and constrained population size and growth, highlight the vulnerability of this C. carcharias population. These findings underscore the importance of ongoing population assessment and evidence-based conservation strategies to ensure long-term viability of C. carcharias populations globally.

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