12 



Fishery Bulletin 102(1) 



fish will certainly increase reproduction and decrease the 

 impact of fishing on the population. However, the benefit of 

 marine reserves will be much greater in populations where 

 larger or older individuals play a key role in reproduction. 

 Given the predicted extreme sensitivity of the protogynous 

 population to the pattern of size-selective fishing, marine 

 protected areas could represent a precautionary manage- 

 ment strategy to ensure that some males are not subject 

 to fishing mortality. 



A comprehensive approach to stock dynamics 



Managing fishing on stocks of sex-changing fish will require 

 considering the sex-change pattern. However, one must also 

 consider the sex change pattern within the context of the 

 mating system. Although the pattern of sex determination 

 does affect the stock dynamics, simple statements regard- 

 ing whether dioecious or sex-changing populations are 

 more sensitive to fishing are not possible. The differences 

 among dioecious and sex-changing stocks are complex, and 

 the management of these stocks will depend as much on 

 their mating system, the type of fishing strategies used 

 to capture them, and mating aggregation size as on the 

 sex determination pattern. Classic SPR measures cannot 

 measure sperm limitation and reduced fertilization rates, 

 and thus will not always measure or predict the impact of 

 fishing mortality on the population. Rather than relying 

 on measures of spawning stock biomass per recruit alone, 

 management groups should also monitor protogynous sex- 

 changing stocks for a reduction in fertilization rates 



Acknowledgments 



We thank Phil Levin, Alec McCall, Steve Ralston, and Bob 

 Warner for their comments on an earlier version of this 

 manuscript. This research was supported by National Sci- 

 ence Foundation grant IBN-01 10506 to Suzanne Alonzo 

 and the Center for Stock Assessment Research (CSTAR). 



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