106 



Fishery Bulletin 102(1 



the new moon. Therefore, the timing of the proposed spawn- 

 ing closures seems appropriate. However, it is not known 

 whether L. carponotatus aggregate to spawn; therefore the 

 goal of protecting spawning aggregations might not be rel- 

 evant for this species. In fact, the prevalence and ecological 

 importance of spawning aggregations for any species on 

 the GBR is largely unknown; therefore the efficacy of the 

 proposed closures is difficult to predict. 



Beyond the implications for management regulations, 

 these data have implications for modeling L. carponotatus 

 stock dynamics. In particular, the results suggest that 

 reproductive output by a unit of L. carponotatus biomass 

 cannot be predicted on the basis of that biomass alone. 

 Relative ovary weight increases slightly with increasing 

 body size and there is evidence that larger fish spawn more 

 frequently. The greatest difference in the proportion of ripe 

 ovaries between size classes occurred in February 1998 af- 

 ter severe flooding in January. It is possible that the lower 

 proportion of ripe ovaries among small fish in February was 

 due to stresses caused by changes in salinity or increased 

 run-off and is not a regular trait. However, increased resil- 

 ience to environmental stresses that allows more frequent 

 spawning would also increase the relative reproductive 

 success of large fish. Therefore, a population comprising 

 fewer larger fish is likely to show greater annual egg pro- 

 duction than a population with equivalent biomass that 

 comprises more numerous but smaller fish. Additionally, 

 the sex-specific patterns reported in this study further 

 suggest gross biomass might be an inadequate index of 

 replenishment potential and that female biomass needs 

 to be considered. Therefore, stock structure, in terms of 

 sex ratio and the frequency of size classes, and not simply 

 overall biomass needs to be considered when predicting 

 reproductive potential. 



Acknowledgments 



I thank the numerous assistants who participated in 

 fieldwork, as well as Sam Adams and Sue Reilly for assis- 

 tance with histological examinations. The manuscript was 

 greatly improved by comments from Howard Choat, Carl 

 Walters, Tony Fowler, Campbell Davies, Sam Adams, Bruce 

 Mapstone, an anonymous thesis examiner, and two anony- 

 mous reviewers. This work was conducted while the author 

 was supported by an international postgraduate research 

 scholarship from the Commonwealth of Australia and a 

 postgraduate stipend from the CRC Reef Research Centre. 

 Final preparation of the manuscript took place while the 

 author was supported by a postdoctoral fellowship funded 

 jointly by the University of Windsor and the Canadian 

 National Science and Engineering Research Council (col- 

 laborative research opportunity grant no. 227965-00) to 

 Peter Sale and others). 



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