New Zealand Journal of Marine and Freshwater Research abstracts

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Longevity, growth, reproduction and a description of the fishery for silver sweep Scorpis lineolatus off New South Wales, Australia

John Stewart
Julian M. Hughes

New South Wales Department of Primary Industries
Cronulla Fisheries Research Centre
P. O. Box 21, Cronulla
NSW 2230, Australia
email: John.Stewart@fisheries.nsw.gov.au

Abstract  Size at age, growth rates, seasonality of spawning, and size at maturity were described for the silver sweep Scorpis lineolatus off the coast of New South Wales, Australia. Estimates of age were made by counting annual zones in sections of otoliths. The ageing technique was validated using young-of-the-year fish, staining fish with tetracycline, and by marginal increment analysis. Silver sweep exhibited extreme longevity with an observed maximum age of 54 years and more than 50% of the fishery being greater than 15 years old. Growth was rapid during the first few years before reaching sexual maturity at 2-3 years and at a length of c. 17 cm fork length, after which growth slowed dramatically. Silver sweep displayed a winter spawning period. The fishery is unusual in that despite heavy fishing pressure and rapidly declining catches the age structure of the catch suggests a population that has been subjected to minimal fishing mortality. It is proposed that the large declines in commercial landings may be the result of serial depletion on local reefs and that current landings are being taken from schools of fish that have received little fishing pressure historically.

Keywords  Scorpis; sweep; longevity; ageing; serial depletion

M04137; Online publication date 17 June 2005 Received 20 September 2004; accepted 20 December 2004
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39: 827-838
0028-8330/05/3904-0827 © The Royal Society of New Zealand 2005

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