Age determination of orange roughy,Hoplostethus atlanticus (Pisces: Trachichthyidae) using210Pb:226Ra disequilibria |
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Authors: | G. E. Fenton S. A. Short D. A. Ritz |
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Affiliation: | (1) Zoology Department, University of Tasmania, G.P.O. Box 252C, 7001 Hobart, Tasmania, Australia;(2) Environmental Radiochemistry Laboratory, ANSTO, Private Mail Bag 1, 2234 Menai, New South Wales, Australia |
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Abstract: | Natural levels of210Pb:226Ra in otoliths of orange roughy,Hoplostethus atlanticus, from south-east Australian waters, were measured to determine fish ages radiometrically. Up to maturity, radiometric age estimates were consistent with a single constant otolith growth rate. Radiometric ages for juveniles were comparable with, but greater than, those obtained in a recent, validated New Zealand study which employed counts of annuli on the surface of otoliths. Beyond maturity, radiometric ages were obtained by modelling with an otolith growth rate set at 45% of the juvenile rate. Radiometric ageing confirms that orange roughy is very slow-growing, with an age at maturity (32 cm standard length, SL) of ~ 32 yr, and is very long-lived, with fish 38 to 40 cm being 77 to 149 yr old. These results have important implications for the management of the fishery. |
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