FISHERY BULLETIN: VOL. 83, NO. 2 



STARVED 



FED 



lOOr 



YOLKED EGGS PRESENT 



50% OR MORE YOLKED 

 OOCYTES a ATRESIA 



• p ATRESIA PRESENT 



A a ATRESIA OF UNYOLKED 

 OOCYTES PRESENT 



30 40 



ELAPSED TIME (days) 



FIGURE 4. — Percentages of captive female northern anchovy 

 with ovaries having various atretic characteristics during a 27-d 

 starvation period and after the onset of feeding. Each percentage 

 is calculated from a sample of 18-24 females (see Tables 1 and 2); 

 alpha, beta, and gamma through delta stages of atretic follicles 

 are those defined by Bretschneider and Duyvene de Wit (1941). 



dominant process became maturation rather than 

 resorption. This was indicated by sharp declines in 

 the percentages of females with alpha stage atre- 

 sia of unyolked oocj^es and beta stage atretic folli- 

 cles, and the reappearance of yolked oocytes (day 

 41). After only 1 wk of feeding the percentage of 

 females with alpha stage atresia from partially 

 unyolked oocytes dropped from 96 to 30%. 



Some inferences can be drawn from these data 

 regarding the duration of atretic stages. The sharp 

 and simultaneous decline in beta stage atretic fol- 

 licles and alpha stage atresia of unyolked oocytes 

 (following the onset of feeding) indicates that 

 alpha and beta stages must have a short and simi- 



lar duration. The duration of alpha and beta atre- 

 sia probably is <2 wk, since the incidence of 

 these two stages dropped to very low levels 2 wk 

 after the onset of feeding; a lag of about 1 wk 

 existed between the first high incidence of females 

 with beta atresia (9 d) and that for gamma -H delta 

 (16 d), indicating that the duration of the beta 

 stage may be about 1 wk. The continued high inci- 

 dence of gamma -I- delta stages of atretic follicles 

 long after the onset of feeding indicates that these 

 late atretic stages must persist in the ovary for 

 much longer periods than alpha or beta stages. 

 Although gamma -I- delta stages were present in all 

 ovaries on the last day of the experiment their 

 abundance within an ovary had decreased indicat- 

 ing that even the delta stage would eventually 

 disappear, eliminating the last histological sign of 

 past reproductive activity. We conclude from these 

 inferences that the alpha and beta stages persist 

 in the ovary for 1 wk or less whereas gamma -i- 

 delta stages persist for over a month, but eventu- 

 ally all signs of past reproductive activity are lost. 



The occurrence of alpha stage atresia of yolked 

 oocytes is the best characteristic to use to back- 

 calculate the time of past reproductive activity in 

 field-caught specimens because the stage is of 

 relatively short duration and the time required to 

 resorb all yolked oocytes is relatively short. On the 

 other hand, alpha stage atresia of unyolked oo- 

 cytes, and beta and gamma -^ delta stages are less 

 useful for back-calculations because these stages 

 may occur in an ovary for extended periods while 

 atretic oocytes are recruited from the large reser- 

 voir of unyolked oocytes in the ovary. In addition, 

 estimates of the time since the onset of atresia in 

 ovaries without yolked oocytes (using the inci- 

 dence of beta or gamma + delta atretic stages) will 

 always be uncertain because atresia of unyolked 

 oocytes may occur at low levels in immature or 

 developing ovaries as well as in regressing 

 ovaries. 



For the laboratory specimens, we calculated the 

 average elapsed time from the onset of ovary re- 

 sorption using various classes of alpha stage atre- 

 sia of yolked oocytes and beta atresia in ovaries 

 without yolked oocytes (Table 3). We prefer the 

 criteria of 50% or more of the yolked oocytes with 

 alpha stage atresia because it is likely that no 

 spawning will occur in such females. The average 

 duration of this stage (alpha, yolked, ^ 50% ) in the 

 starving laboratory females was about 9 d and 

 ranged from <3 to 20 d from the onset of starva- 

 tion. 



Starvation may have induced a higher rate of 



128 



