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Ichthyoplankton-based spawning dynamics of blue mackerel (Scomber australasicus) in south-eastern Australia: links to the East Australian Current

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Neira, FJ and Keane, JP (2008) Ichthyoplankton-based spawning dynamics of blue mackerel (Scomber australasicus) in south-eastern Australia: links to the East Australian Current. Fisheries Oceanography, 17 (4). pp. 281-298. ISSN 1054-6006

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Abstract

We describe findings of three ichthyoplankton surveys undertaken along south-eastern Australia during spring(October 2002, 2003) and winter (July 2004) to examine spawning habitat and dynamics of blue mackerel (Scomber australasicus). Surveys covered 860 nautical miles between southern Queensland (Qld; 24.6S) and southern New South Wales (NSW; 41.7S), and were mainly centred on the outer shelf including the shelf break. Egg identifications were verified applying mtDNA barcoding techniques. Eggs (n = 2971) and larvae (n = 727; 94% preflexion) occurred both in spring and winter, and were confined to 25.0–34.6S. Greatest abundances (numbers per 10 m2) of eggs (1214–7390) and larvae (437–1172) occurred within 10 nm shoreward from the break in northern NSW. Quotient analyses on egg abundances revealed that spawning is closely linked to a combination of bathymetric and hydrographic factors, with the outer shelf as preferred spawning area, in waters 100–125 m deep with mean temperatures of 19–20C. Eggs and larvae in spring occurred in waters of the East Australian Current (EAC; 20.6–22.3C) and mixed (MIX; 18.5–19.8C) waters, with none occurring further south in the Tasman Sea (TAS; 16.0–17.0C). Results indicate that at least some of the south-eastern Australian blue mackerel stock spawns during winterspring between southern Qld and northern NSW, and that no spawning takes place south of 34.6S due to low temperatures (<17C). Spawning is linked to the EAC intrusion, which also facilitates the southward transport of eggs and larvae. Since spring peak egg abundances came from where the EAC deflects offshore, eggs and larvae are possibly being advected eastwards along this deflection front. This proposition is discussed based on recent data on blue mackerel larvae found apparently entrained along the Tasman Front.

Item Type: Article
Keywords: East Australian Current, eastern Australia, ichthyoplankton, pelagic fishes, Scomber australasicus, shelf spawning
Journal or Publication Title: Fisheries Oceanography
Page Range: pp. 281-298
ISSN: 1054-6006
Identification Number - DOI: 10.1111/j.1365-2419.2008.00479.x
Additional Information: The definitive published version is available online at: http://interscience.wiley.com
Date Deposited: 17 Sep 2008 00:02
Last Modified: 18 Nov 2014 03:49
URI: http://eprints.utas.edu.au/id/eprint/7471
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