328 



Fishery Bulletin 94(2). 1996 



3 

 2 i 



i' 1 8 



cr 

 ■-t | -> 



0.6 



2 4 (. S 10 12 14 1() 18 20 22 24 26 

 Age (years) 



Figure 8 



Catch curves for L. quinquelineatus from Lodestone Reef between suc- 

 cessive years, based on observed ages. 



tality rates among reefs for these species are likely 

 to be authentic and not a product of the assumptions 

 inherent in the use of catch curves. 



In conclusion, this study demonstrated that sig- 

 nificant variability exists in the mortality and age 

 structures of L. adetii and L. quinquelineatus at the 

 spatial scale of individual reefs. The demography of 

 both these lutjanid species at the spatial scale of in- 

 dividual coral reefs is most likely to be a consequence 

 of the nonequilibrial balance of variable recruitment 

 interacting with density-independent mortality 

 (Doherty and Fowler, 1994b). This spatial variabil- 

 ity in demographic parameters among reefs should 

 be considered in the development of management 

 models. The significant differences in mortality rates 

 and age structures for the populations of L. adetii 

 and L. quinquelineatus among reefs would have more 

 impact on management models than the small dif- 

 ferences in growth for these species. Further, greater 

 longevity conveys a selective advantage by increasing 

 the cumulative lifetime fecundity (egg production) of 

 the female parent (see Beverton, 1987). Therefore, in 

 terms of the current management models of the Great 

 Barrier Reef Marine Park, it would be advantageous 

 to protect reefs that are characterized by species with 

 extended longevity and low rates of natural mortality 

 (in comparison with reefs of similar population size but 

 which are characterized by fish with reduced longevity 

 and high rates of natural mortality). The primary ad- 

 vantage of adopting this strategy would be that the 

 spawning biomass of the longer lived fishes would be 

 protected which has the capacity to act as a recruit- 

 ment source for the surrounding areas that are fished. 



Acknowledgments 



This work was undertaken while S. J. Newman was a 

 postgraduate fellow at the Australian Institute of Ma- 

 rine Science and contributes in part to the requirements 

 for a Ph.D. degree to S. J. Newman from James Cook 

 University of North Queensland. We gratefully ac- 

 knowledge financial support from Australian Research 

 Council grants to D. McB. Williams and G. R. Russ 

 and logistical support from the Australian Institute of 

 Marine Science. We thank the crew of the RV Lady 

 Basten , the RV The Harry Messel, and the RV Hercules, 

 as well as volunteers who assisted with fieldwork. 



Literature cited 



Beverton, R. J. H. 



1987. Longevity in fish : some ecological and evolutionary 

 considerations. In A. D. Woodhead and K. H. Thompson 

 (eds.), Evolution of longevity in animals: a compariative 

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 Beverton, R. J. H., and S. J. Holt. 



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 Cerrato, R. M. 



1990. Interpretable statistical tests for growth comparisons 

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 Chen, Y., D. A. Jackson, and H. H. Harvey. 



1992. A comparison of von Bertalanffy and polynomial func- 

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 Davis, T. L. O., and G. J. West. 



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