HUNTER and MACEWiCZ: ATRESIA IN NORTHERN ANCHOVY OVARY 



maximum time was 29 d. Thus the effect of atresia 

 on fecundity may be underestimated since the du- 

 ration of atretic stages is short and a small stand- 

 ing stock of atretic oocytes could be an indication 

 of a high loss rate. On the other hand, laboratory 

 studies seem to indicate that atretic rates are not 

 sufficiently high to account for the differences in 

 fecundity observed when fish are fed high and low 

 rations (Tyler and Dunn 1976; Wootton 1979). The 

 duration of the atretic stages in these studies was 

 unknown, however. 



Additional evidence for the volatility of the re- 

 productive state of anchovy is an important con- 

 tribution of this study. Our laboratory data indi- 

 cated that given a shortage of food the ovary can be 

 rapidly resorbed leaving no trace of former repro- 

 ductive activity in a few months or less, but when 

 given sufficient food atresia stopped, maturation 

 and vitellogenesis resumed, and a reproductively 

 active ovary was rapidly reformed within 35 d. 

 Clearly, in such multiple spawning fishes as the 

 anchovy, more than one spawning season per year 

 is possible given the appropriate environmental 

 conditions. This may explain the occurrence of a 

 second annual spawning period in the Peruvian 

 anchoveta (Santander and Castillo 1976) and the 

 occasional heavy fall spawning of the northern 

 anchovy ( Smith 1972 ). That active ovaries are con- 

 sistently produced from small, inactive ones in 

 30-60 d in the laboratory (Leong 1971; Hunter and 

 Leong 1981) and that some reproductively active 

 females are found the year around also supports 

 this view. 



Food shortage does not always lead to regression 

 of the ovary in anchovy or any other multiple 

 spawning fishes. In addition to food ration, regres- 

 sion of the ovary also depends upon the level of 

 energy reserves, the timing of the reproductive 

 cycle, and perhaps certain environmental condi- 

 tions such as temperature and day length. For 

 example, starvation of 40-80 d did not block the 

 initial increase in the size of ovaries of the goby 

 Gillichthys at the start of the reproductive cycle in 

 July but only 23 d of starvation resulted in ovarian 

 regression in January when active vitellogenesis 

 was occurring (de Vlaming 1971). Similarly we 

 noted in a preliminary experiment that starving 

 anchovy of 25^f greater wet weight than those 

 used in this study produced a slower regression of 

 the ovary over a 36-d period than occurred in the 

 present study. The present study is more represen- 

 tative of natural conditions since the fish were 

 taken in midspawning season when their ovaries 

 were active whereas in the preliminary study the 



fish were taken out of season and fed heavily for 30 

 d to induce gonad maturation before the onset of 

 the 36-d starvation period. 



Another important conclusion from this study 

 was that young female anchovy spawning for the 

 first time probably have a much shorter reproduc- 

 tive season than do older females. Hunter and 

 Leong (1981) estimated that the average female 

 spawns about 20 times per year. Thus the older 

 females must spawn considerably more often than 

 20 times per year, and probably contribute a much 

 larger fraction of the reproductive output of the 

 population than a proportionate share by weight. 

 This indicates the importance of maintaining 

 older fish in the population and that danger may 

 exist if older fish are overharvested. 



ACKNOWLEDGMENTS 



We thank Roderick Leong (Southwest Fisheries 

 Center (SWFO) for providing and maintaining 

 the northern anchovy used in the laboratory study. 

 We thank Kenneth Mais (California Department 

 of Fish and Game) for providing some specimens. 

 Pedro Paloma (SWFC) and Eric Lynn (SWFC) as- 

 sisted in histological classifications. Carol Kim- 

 brell (SWFC) and Susan Picquelle (SWFC) pro- 

 vided valuable assistance in analyzing the data. 



LITERATURE CITED 



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