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Water mass selectivity by larvae of small pelagic fishes in south-eastern Australian shelf waters: a proxy for key spawning habitats

John Keane, Francisco Neira and Jeremy Lyle

Marine Research Laboratories, Tasmanian Aquaculture and Fisheries Institute, Private Bag 49, Hobart, Tasmania 7001 Australia Email: jpkeane@utas.edu.au

Abstract

Larval habitats of six small pelagic fishes, namely Etrumeus teres, Sardinops sagax, Engraulis australis, Emmelichthys nitidus, Trachurus spp. and Scomber australasicus, are described and compared along the south-eastern Australian shelf based on links with discrete water masses and other oceanographic features in the region. Data comes from five intensive ichthyoplankton surveys conducted between southern Queensland and north-eastern Tasmania (~1050 nm) in 2002-2004. Three major water masses were identified in the region during surveys, i.e. East Australian Current (EAC), Tasman Sea (TAS), and a composite mixed water mass (MIX). Taxa distributions were strongly linked to these water masses, shifting southwards following the strengthening of the EAC. Larvae of E. teres, S. sagax, E. australis, and S. australasicus were strongly associated with EAC and MIX water, with greatest abundances typically occurring near the EAC-MIX interface or in upwelling areas where the EAC separates from the coast. Larval Trachurus spp., comprising two closely-related species (T. novaezalandiae and T. declivis), were highly abundant across all water masses, although preliminary analyses of postflexion stages suggest differing preferences. Larvae of E. nitidus were restricted to cooler TAS water. Results highlight the close affinity between larval distributions and discrete water masses, implying that these may be used as a proxy to identify potential spawning areas.

Key Words

Larval fish assemblages, small pelagic fishes, water masses, oceanography, East Australian Current, Tasman Sea.

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