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Fishery Bulletin 94|1). 1996 



examined for the presence of alpha (a), beta (/3), 

 gamma (7) or delta (5) stage atresia (Bretschneider 

 and Duyvene de Wit, 1947). Our definition of an 

 atretic follicle, which characterizes an oocyte under- 

 going atresia in fi or subsequent atretic stages, was 

 adopted from Hunter and Macewicz ( 1985b). 



Because females tend to reabsorb their oocytes once 

 the spawning season comes to an end, the criteria of 

 50% or more of yolked oocytes (not those in early 

 vitellogenic stages) with a-stage atresia, or the ab- 

 sence of yolked oocytes but presence of postovulatory 

 follicles or atretic follicles, or both, were used to in- 



dicate that these females had finished their spawn- 

 ing season (Hunter and Macewicz, 1985, a and b; 

 Hunter et al., 1986; Dickerson et al., 1992; Macewicz 

 and Hunter, 1993). It should be mentioned that the 

 occurrence of a-stage atresia in yolked oocytes is the 

 best characteristic to backcalculate the time of past 

 reproductive activity because the type of oocyte un- 

 dergoing atresia is still discernible, and this atretic 

 oocyte can be easily distinguished from postovulatory 

 follicles (Hunter and Macewicz, 1985b). Hence, all 

 the yolked oocytes (not those in early vitellogenic 

 stages) in each section were counted under the mi- 



