Shelf-ocean connectivity: the role of eddies in cross-shelf exchange of larval fishes off SW Australia
Holliday, D., Beckley, L.E., Feng, M. and Waite, A.M. (2009) Shelf-ocean connectivity: the role of eddies in cross-shelf exchange of larval fishes off SW Australia. In: AMSA2009 46th Annual Conference for the Australian Marine Sciences Conference, 5 - 9 July, Adelaide, Australia.
It has been hypothesised that larvae of neritic fishes are exposed to cross-shelf (offshore) transport during formation of meso-scale anti-cyclonic eddies of the Leeuwin Current and this could result in increased larval mortality and reduced recruitment. A month-long multidisciplinary voyage in May 2006 off south-western Australia allowed for in situ examination of the meso-scale oceanography and the process of cross-shelf transport during formation of an anti-cyclonic eddy. Coupled with oceanographic analyses, larval fish assemblages were used as tracers to ascertain the timing, sources and pathways for the incorporation of neritic larval fishes into an eddy. Distinct larval fish assemblages characterised the shelf, meander/eddy and surrounding ocean. Compared with the surrounding ocean, larval fishes were concentrated in the eddy and the assemblage was a mixture of both meso-pelagic and neritic species. The Leeuwin Current was identified as the major transport route for the incorporation of neritic larval fishes into the eddy. Prior to this, mixing between Leeuwin Current and shelf waters occurs through upstream incursions of the current onto the shelf and this appears to be important for the initial entrainment of neritic larvae. In contrast, high concentrations of early-stage larvae of meso-pelagic fishes (e.g. Myctophidae) in the eddy appear to be the product of localised spawning in or near the eddy. Night-time vertical distributions of larval fishes showed high concentrations in the upper 80m of the water column and patterns were investigated relative to thermal stratification, the deep chlorophyll maximum and the horizontal velocity field.
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|Murdoch Affiliation:||School of Environmental Science|
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