240 



Fishery Bulletin 103(2) 



1 o i A Rule 1 : Fixed 

 



L,=30r=1 



1 

 08 

 0.6 



0.4 ' 

 02 

 







0.5 



1 



1.5 



1 C Rule 3: Relative frequency 

 0.8- 



0.6- . ..„■■.... 



04 



0.2 







1.0 



2.5 



L r =35 r=1 



L,=25 r=1 



\ L,=30r=0.1 



0.5 



1.5 



2.5 



0.5 1 1.5 2 



Fishing mortality 



2.5 



L,=30r=1 



L,=30r=1 



L,=30r=1 



Figure 5 



The effect of size-selective fishing on the predicted population sex ratio 

 for all four patterns of sex change. We present results for a sex-changing 

 stock with one mating site. Means across 20 simulations are given. For 

 details see text. The same basic patterns are predicted with multiple 

 mating sites. A line is not shown in panel A (when sex change is fixed I 

 where L,= 30 and r=0.1 because the population is predicted to crash at 

 any fishing mortality in this scenario. 



Spawning-per-recruit (SPR) measures and 



a comparison of protogynous and dioecious stocks 



Our previous results (Alonzo and Mangel. 2004) have 

 shown that whether species change sex or are dioecious 

 is predicted to have dramatic effects on both the stock 

 dynamics and performance of classic SPR measures. 

 However, our results show that the exact pattern of 

 sex change, and not just whether the pattern is plastic 



or fixed, can have a strong effect on these measures as 

 well (Fig. 7). Because of the population dynamics of the 

 model, all the scenarios represented in the present study 

 show a great resiliency to fishing. Hence, the predicted 

 changes in stock size are all above the common threshold 

 of allowing a reduction of spawning per recruit mea- 

 sures to 40% of their values in the unfished condition. 

 However, our aim is not determine if this population is 

 overfished. Instead, it is to determine whether classic 



