Alonzo and Mangel; Sex-change rules, stock dynamics, and the performance of spawnmg-per-recruit measures in protogynous stocks 235 



ever, the exact pattern of sex change has an important 

 and qualitative effect on the predicted stock dynamics 

 (Table 2). All three plastic patterns of sex change are 

 predicted to show lower sperm limitation and higher fer- 

 tilization rates in the presence of fishing than the fixed 

 pattern of sex change (Table 2). However, associated 

 with plastic sex change is also a greater predicted drop 

 in egg production (total and fertilized) and mean popula- 

 tion size than when the effect of size on the probability 

 of sex change is fixed (Fig. 1, Table 2). This drop in egg 

 production and mean population size occurs because 

 female biomass is predicted to decrease as a result of the 

 combination of fishing on larger individuals and smaller 



sizes at sex change (Fig. 2). The basic patterns are the 

 same for the case with multiple mating sites. Most of 

 the significant reductions in stock size are predicted 

 at high fishing mortality. However, it is important to 

 remember that we have assumed that the stock is very 

 resilient (Table 1), and our focus is on the differences 

 among sex-change rules and fishing patterns rather than 

 on absolute fishing mortality. 



The effect of mating group size 



Although mating group size is predicted to have an effect 

 in most cases on the stock dynamics of the population. 



