336 



Fishery Bulletin 91(2), 1993 



terms of egg production. The possibility exists that ex- 

 ploitation could reach a level at which males are elimi- 

 nated at such a rate that females are forced to transform 

 faster or at an earlier size. The optimal sex ratio, from a 

 behavioral perspective, has not yet been determined for 

 C. straita. As suggested by the sensitivity analysis, sub- 

 stantial changes in the transformation rate could signifi- 

 cantly alter the contributions of a cohort to the spawning 

 biomass. There is no information currently available to 

 determine the controlling mechanism or degree of plas- 

 ticity for transformation rates within a population. 



Future refinements of this distributed delay model 

 may provide a more detailed picture of the effects of 

 harvest on species such as black sea bass. Density- 

 dependent feedback mechanisms influencing transi- 

 tion rates and age-at-first-transformation will ulti- 

 mately be incorporated into the model to examine 

 theoretical implications. A time-varying distributed 

 delay model is also possible to account for seasonal 

 changes in growth and mortality. With a minimal 

 amount of growth information, either from back-cal- 

 culations or tagging data, and some reasonable esti- 

 mates of other important life-history events, we be- 

 lieve the distributed delay model can provide an 

 effective length-based alternative to traditional dy- 

 namic pool models. 



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