HUNTER and MACEWICZ: ATRESIA IN NORTHERN ANCHOVY OVARY 



follicles indicate that some of the females in atretic 

 state 1 spawn despite the atretic condition of their 

 ovaries. On the other hand, only two females 

 classed in atretic state 2 had a recent history of 

 spawning. These two females had few yolked 

 oocytes remaining, all but one was in alpha 

 atresia. This atresia may have increased or even 

 started during the time elapsed between hydra- 

 tion and capture. In short, the females in atretic 

 state 2 probably did not spawn in the highly 

 atretic state in which they were captured. No 

 doubt exists that females with moderate levels of 

 ovarian atresia are capable of spawning because 

 they often are hormonally induced to do so in the 

 laboratory. In summary these data indicate that 

 significant numbers of females in atretic state 1 

 may continue to spawn under natural conditions, 

 although the probability of spawning appears to 



be about half that offish without ovarian atresia. 

 Few or none of the females in atretic state 2 con- 

 tinue to spawn indicating that this stage is proba- 

 bly the best one to use to calculate cessation of 

 spawning in the population. 



Forcasting the end of Spawning 

 Using Ovarian Atretic States 



In our laboratory study atretic state 1 had an 

 average duration of about 5 d and atretic state 2, 9 

 d; state 3 was in excess of 16 d and probably per- 

 sists for 30 or more days (Table 3). In the sea, 

 linear projections of the end of the spawning sea- 

 son from early incidence of atresia is not realistic 

 since the numbers of females with regressing 

 ovaries would be expected to increase sharply at 

 the end of the season. 



listed in order of collection dates for southern and Baja California (1977-82) and for 

 (1979, 1982). 



^New postovulatory follicles <24 h old, 



^Postovulatory follicles about 24 h old 



"Female not examined histologically, ovary ^1% of body weight. 



^Female northern anchovy from northern California; rest of females were from southern and Baja California. 



131 



