826 



Fishery Bulletin 97(4), 1999 



age-length (both age-based data), and tagging data 

 (length-based) showed agreement for fish aged 2-4 

 years but varied for fish with one growth zone. Dif- 

 ferences in rates of growth were greater for younger 

 fish than for older fish and may have been caused by 

 inaccuracies in aging, influence of tagging on growth 

 (e.g. McFarlane and Beamish, 1990), within- or 

 between-year differences, and variations in year-class 

 strength. Although estimates of growth from tagging 

 data provide some indication that age-length data 



1.000 

 800 

 600 

 400 

 200 

 



3 4 



Age (years) 



Figure 9 



MULTIFAN growth curve for the length-frequency data. A 

 model incorporating seasonal growth is shown. Values of ^i, 

 A', and L , (mm) are shown. 



may be reasonable, they should not be used as a 

 means of validation (see Francis, 1988a). 



Tagging data also suggest that S. lalandi in New 



South Wales has greater annual growth than the 



same species in New Zealand and the United States 



(Baxter, 1960; Holdsworth^). For S. lalandi in New 



South Wales, annual growth rates of 144 mm were 



found for 500-mm-FL fish, compared with 93 mm 



(New Zealand) and a range of 34-109 mm (US) for 



similar size fish. In New Zealand, annual growth of 



44 mm was found for 1000-mm-FL fish, which is 



within the range found in the United States ( 19- 



70 mm). Few large fish were tagged in New South 



Wales, preventing estimates of annual growth at 



this larger size. 



Practicalities of aging kingfish 



With the exception of dorsal spines, which did not 

 appear useful for aging kingfish, only scales can 

 be easily collected without altering the market 

 value of the fish because Seriola lalandi are pref- 

 erentially sold whole in NSW. Scales showed simi- 

 lar estimates of mean size-at-age to otoliths for all 

 age classes except fish with one growth zone, but 

 their use in aging kingfish can only be recom- 

 mended with caution until the position of the first 

 gi'owth zone is better understood. The usefulness 

 of otoliths and vertebrae may be limited 

 by the cost offish, but, if possible, col- 

 lections of at least one of these struc- 

 tures should be made. The similarity of 

 age estimates among structures sug- 

 gests that, if validations are possible, 

 kingfish may be aged reliably. 



Acknowledgments 



This research was supported by the 

 Fisheries Research Development Corpo- 

 ration and NSW Fisheries. We thank 

 the processors at the Sydney Fish Mar- 

 kets, commercial fishermen, NSW Fish- 

 eries staff and Martin Tucker for supply- 

 ing fish. We also thank Norm Lenehan 

 for help with processing vertebrae, and 

 Duncan Worthington and Malcolm 

 Haddon for statistical advice and nu- 

 merous discussions regarding aging of 

 fish. We are particularly grateful to 



Holdsworth, J. C. 1997. Ministry of Fisher- 

 ies, 17 Keyte Street, Kensington, private Bag 

 901.3, Whangarei. New Zealand. Unpubl. data. 



