01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-02-0055 |
| Title of Abstract | Heading south! Contrasting larval fish assemblages and taxonomic distinctness in the Agulhas and Leeuwin boundary current systems |
| Authors | Lynnath E. Beckley*, Alicia Sutton |
| Organisation | Murdoch University |
| Address | Murdoch University Perth, WA, Australia Pincode: 6150 E-mail: L.Beckley@murdoch.edu.au |
| Country | Australia |
| Presentation | Oral |
| Abstract | The Indian Ocean has unique boundary currents that flow poleward on both sides of the ocean basin adjacent to southern Africa and western Australia. Fish larvae in both boundary current systems have been independently investigated, but for the Agulhas Current system, this presentation provides the first analyses of seasonal ichthyoplankton assemblages. Early winter assemblages were compared across both the Agulhas and Leeuwin Current systems. Average Taxonomic Distinctness (Ave TD; relationship of every pair of species via levels in the Linnean classification tree) was calculated for each isobath and latitude sampled based on presence/ absence of fish taxa in each system. In the Agulhas Current system, Scomber japonicus, Sardinops sagax and Etrumeus whiteheadi were found to drive most of the differences between isobaths, being most abundant in shelf waters in all seasons. During summer, Auxis rochei differentiated mid-shelf and slope assemblages from other isobaths, and the families Myctophidae, Notosudidae and Gonostamatidae distinguished oceanic assemblages. In winter, the Leeuwin Current system was dominated by the myctophid genus Diaphus, Sardinops sagax and Vinciguerria nimbaria. The Ave TD of larval fish assemblages was similar for both the Agulhas Current (89.84 ± 0.85) and the Leeuwin Current (90.74 ± 0.99) systems. In both, oceanic assemblages tended to exhibit higher Ave TD, whilst it was similar across latitude for both oceanic and slope assemblages. Ave TD increased towards the south for Agulhas Current shelf assemblages but not for those of the Leeuwin Current. Overall, nMDS ordination showed larval fish assemblages from both current systems to be clearly delineated from each other. In terms of environmental factors, sea surface temperature, water depth and latitude returned the best correlations with larval fish assemblages from both sides of the Indian Ocean basin. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Agulhas Current, Leeuwin Current, larval fish assemblages, Taxonomic Distinctness |
| For Awards | no |