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Larval fish assemblages and particle back-tracking provide insight into Eastern Indian Ocean boundary current processes

Beckley, L.E., Holliday, D., Weller, E., Millar, N., Olivar, M.P., Feng, M., Slawinski, D. and Thompson, P.A. (2011) Larval fish assemblages and particle back-tracking provide insight into Eastern Indian Ocean boundary current processes. In: 48th Annual Conference of the Australian Marine Science Association, 3 - 7 July, Fremantle, Western Australia.


Synoptic examination of the Leeuwin Current (LC) system along the Western Australian continental shelf and adjacent ocean (22°S–34°) during the late austral autumn of 2007 was accompanied by a depth-integrated, bongo-net survey of the associated larval fish assemblages. The temperature and salinity signature of the LC experienced substantial modification as it flowed south; surface temperature of the LC decreased by ~5.25°C while surface salinity increased by ~0.72 psu. Comparison of these empirical data with the Bluelink re-analysis product (based on the hydrodynamic model OFAM) revealed the model to provide a good representation of the oceanography of the LC system. Larval fishes were highly diverse comprising >200 taxa from 114 neritic and oceanic teleost families. Two-factor PERMANOVA indicated significant structuring of larval fish assemblages both latitudinally and across isobaths with a significant interaction term. MDS ordination of larval fish assemblages showed clustering of northern inner shelf stations (22oS - 28oS) with that of a developing meso-scale eddy at the 27oS oceanic station. Results from particle back-tracking indicated that, in the previous month, this eddy had strong connection with surface shelf waters from as far north as Northwest Cape at ~22oS. Larval fish assemblages at shelf break and oceanic stations throughout the study area had high similarity and clustered with inner shelf stations south of 29oS indicative of geostrophic inflow, entrainment of Subtropical Water and mixing of regional water masses from the continental shelf. Although the particle back-tracking uses passive kernels, and larvae of marine fishes are known to have complex behavioral and physiological capabilities which can influence their transport, this study has demonstrated broad-scale advection of planktonic biota, both across the shelf, and alongshore in the Eastern Indian Ocean.

Item Type: Conference Item
Murdoch Affiliation(s): School of Environmental Science
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