812 



Abstract.— Dorsal spines, otoliths, 

 scales, and vertebrae collected from 

 yellowtail kingfish (Seriola lalandi) in 

 NSW, Australia, were assessed for use- 

 fulness in estimating age. Legibility of 

 growth zones, the time scale at which 

 zones form, and precision of age esti- 

 mates were evaluated for fish sizes 

 from 323 to 1090 mm FL. All calcified 

 structures contained growth zones, but 

 dorsal spines were unsuitable for age 

 determination because it was likely 

 that early growth zones were lost. From 

 marginal increment analysis, it ap- 

 peared that one zone was laid down per 

 year for otoliths and possibly scales, but 

 a clear pattern was not found for ver- 

 tebrae. Although exact agreement be- 

 tween repeated age readings was rela- 

 tively low (50-669!-), agreement within 

 one zone was higher (92-96'7f) and 

 scales provided the most precise read- 

 ings. Precision decreased with increas- 

 ing age of fish. Growth curves derived 

 from otoliths and scales were similar 

 for all ages except fish from the first 

 age class; those derived from otoliths 

 and vertebrae were similar for all fish 

 with less than eight growth zones. Al- 

 though statistical differences were 

 found between the growth curves of 

 scales and vertebrae for some age 

 classes, with the exception of the first 

 age class these differences were not bio- 

 logically important. Growth rates esti- 

 mated from length-frequency (age- 

 based) and mark-recapture (length- 

 based) data compared favorably with 

 those estimated from calcified aging 

 structures. Otoliths, scales, and verte- 

 brae all showed promise as structures 

 for aging kingfish, but further work is 

 needed to determine the position of the 

 first zone and to validate estimates for 

 all age classes. Until such work is com- 

 pleted, we recommend that scales and 

 either otoliths or vertebrae be used for 

 aging kingfish. 



Aging methods for yellowtail kingfish, 

 Seriola lalandi, and results from 

 age- and size-based growth models 



Bronwyn M. Gillanders 



NSW Fisheries Research Institute 



PO Box 21, Cronulla, NSW 2230, Australia 



Present address: School of Biological Sciences A08 



University of Sydney 



New South Wales 2006, Australia 

 E-mail address bronwynia'bio usyd edu au 



Douglas J. Ferrell 



Neil L. Andrew 



NSW Fisheries Research Institute 



PO Box 21 



Cronulla, New South Wales 2230, Australia 



Manuscript accepted 9 December 1998. 

 Fish. Bull. 97:812-827 (1999). 



Yellowtail kingfish, Seriola lalandi, 

 is a popular recreational species and 

 supports significant commercial 

 fisheries throughout temperate re- 

 gions of the world. In Australia, the 

 major commercial fishery for yel- 

 lowtail kingfish is in New South 

 Wales where 400-600 tonnes are 

 caught per year. Despite the exist- 

 ence of a commercial fishery and 

 persistent controversy about exploi- 

 tation of the species, very little is 

 known about its biology. For future 

 management of the fishery and for 

 stock assessment purposes, informa- 

 tion on age and growth is needed. 



Estimates of age of Seriola spp. 

 have been derived from a variety of 

 methods and structures, reflecting 

 the difficulty of aging Seriola and 

 other pelagic species. The Japanese 

 species (Seriola quinqueradiata) is 

 the most studied species in the ge- 

 nus because of its importance in 

 aquaculture. Studies in the 1950s 

 used scales, vertebrae, and opercu- 

 lar bones for aging (e.g. Mitani, 

 1955, 1958; Mitam and Sato, 1959). 

 More recent studies have focused on 

 the use of vertebrae (e.g. Munekiyo 

 et al., 1982; Murayama, 1992). 

 Scales have also been used to age 

 S. lalandi (formerly S. dorsalis. 



Baxter, 1960), as have otoliths 

 (Penney^). Recently, sectioned oto- 

 liths were used to determine ages 

 ofSeriola dumerili, although it was 

 acknowledged that age and growth 

 determinations were difficult (Man- 

 ooch and Potts, 1997). Despite the 

 use of a variety of structures for ag- 

 ing Seriola spp., there has been no 

 comparative analysis to determine 

 which structure provides the most 

 reliable estimates. In addition, most 

 studies have assumed that growth 

 zones are annual and there have 

 been few validations of age estimates 

 (but see Mitani and Sato, 1959; 

 Baxter, 1960). 



The specific objectives of this 

 study were 1) to assess the useful- 

 ness of several structures (scales, 

 otoliths, dorsal spines, and verte- 

 brae) for determining the age of 

 kingfish, 2) to compare multiple age 

 estimates for different structures in 

 order to determine the most precise 

 method for determining age and 

 growth parameters, 3) to provide 

 information on size-at-age and 4) to 

 compare growth rates obtained 



Penney, A. J. 1992. Sea Fisheries Re- 

 search Institute, Private Bag X2, Rogge Bay 

 8012, South Africa. Personal commun. 



