Oral Presentation Australian Society for Fish Biology & Australian Freshwater Sciences Society Conference 2026

Population structure of bottlenose wedgefish (Rhynchobatus australiae) in the Eastern Indo-West Pacific (145645)

Muhammad Ichsan 1 , Ross G Dwyer 1 , Andhika P Prasetyo 2 , Madeline Green 3 , Fahmi Fahmi 4 , Selvia Oktaviyani 4 , Alexis L Levengood 1 , Barbara Wueringer 5 , Alastair V Harry 6 , Matias Braccini 6 , Karissa O Lear 7 , Nicolas Lubitz 8 9 , Adam Barnett 8 9 , Ilhanum Badawiyah 10 , Samuel M Williams 11 , Bonnie J Holmes 1
  1. University of Sunshine Coast, Sippy Down, Queensland, Australia
  2. Research Centre for Applied Zoology, , National Research and Innovation Agency, Bogor, West Java, Indonesia
  3. University of Tasmania, Hobart, Tasmania, Australia
  4. Research Centre for Biota Systems, National Research and Innovation Agency, Jakarta, Indonesia
  5. Sharks And Rays Australia, Australia, Cairns, Queensland, Australia
  6. Department of Fisheries, Perth, Western Australia, Australia
  7. Murdoch University, Perth, Western Australia, Australia
  8. College of Science and Engineering, James Cook University, Townsville, Queensland, Australia
  9. Biopixel Oceans Foundation, Smithfield, Queensland, Australia
  10. Brawijaya University, Malang, Central Java, Indonesia
  11. Department of Agriculture and Fisheries, Brisbane, QLD, Australia

Understanding population structure and connectivity is fundamental to effective species management, particularly in critically endangered species. Wedgefish are the most threatened group of marine animals facing high anthropogenic threats, especially in the Eastern Indo-West Pacific (EIWP) region. Here, we examine the population structure and connectivity of the bottlenose wedgefish (Rhynchobatus australiae) across the EIWP using next-generation single nucleotide polymorphism (SNP) analyses using 133 samples collected from Indonesia and Australia. Currently, there are limited studies on wedgefish population structure, which have been hindered by small sample sizes, limited seascape/fishery coverage, and outdated genomics approaches. Here, we determined that population structure varied across the EIWP, with strong links between R. australiae captured in the Java Sea and Karimata Strait, as well as among R. australiae captured in Australian waters. Results showed a moderate level of genetic differentiation (mean FST = 0.096, P < 0.01); similar levels of heterozygosity and a low inbreeding coefficient among locations (Ho = 0.172 – 0.278; HE = 0.164 – 0.272, FIS = -0.023 – 0.006). Genetic variation among populations generated from the AMOVA test was ΦST = 0.339, p<0.001. Within Indonesian waters, samples collected from sites in the Inner Sunda Shelf showed high clustering, whereas the Outer Sunda Shelf were isolated from the others. Australian samples clustered together, separated from Inner and Outer Sunda Shelf samples. We recommend strengthening stock-specific fisheries management in heavily exploited Indonesian seascapes and implementing coordinated multilateral management for genetically connected regions to support population sustainability and maintain gene flow between regions.