Note Llanos-Rivera and Castro: Egg-size variation of Engraul/s ringens 



209 



80 

 60 

 40 

 20 

 

 „ 80 



& 60 



c 



<D 



= 40 



(D 



^ 20 





 80 



60 



40 



20 







Valparaiso (33°) 



middle 



15-0.19 020-0.24 0.25-0.29 0.30-0.34 35-0 39 0.40-0.44 



80 



60 - 



40 



20 







80 

 60 - 

 40 

 20 - 



Talcahuano (36 ) 



o 



80 

 60 

 40 

 20 

 



0.15-0.19 020-0.24 0.25-0.29 0.30-0 34 0.35-0 39 0.40-0.44 



Size interval (mm 3 ) 



Figure 2 



Seasonal variation in egg size of the anchoveta (£. ringens) off Valparaiso and Talcahuano. y-axis is frequency over 

 the total number of eggs measured at each locality. Initial, middle, and final are subperiods within the spawning 

 season (see Table 2). 



was much larger (33% larger) than the yolk volume of the 

 larvae hatched in Antofagasta (0.098 mm 3 ). 



Discussion 



The results of this study identified several trends that 

 are related to egg-size variation. First, egg size tends to 

 decrease with the progression of the spawning season. 

 Second, egg size increases with latitude during the peak 

 spawning period. Third, larval size at hatching is smaller 

 in the northern latitude populations. Fourth, the yolk sac 

 of recently hatched larvae is much larger than expected 



(based on the larval size at hatching) in the southern 

 population. 



A number of hypotheses have been proposed to ex- 

 plain egg-size variations in fish that spawn at multiple 

 times as the reproductive season progresses. It has been 

 proposed that in clupeiforms, the decrease in egg size 

 may result from maternal reduction of energy reserves 

 over the spawning season, a switch in the stored energy 

 from reproduction to growth, seasonal changes in the age 

 structure of the spawning population, or changes during 

 ovogenesis that are correlated with temperature (Blaxter 

 and Hunter, 1982; Chambers, 1997, for a recent review). In 

 the anchoveta E. ringens, published data suggest that some 



