210 



Fishery Bulletin 102(1) 



80 

 60 

 40 

 20 

 



80 -p 

 60 -- 

 40 

 20 

 



80 

 60 

 40 

 20 







80 



20-- 



20 S 



n 



.I ii 



23 S 



36 >S 



-+- 



10-0 14 15-0 19 20-0 24 0.25-0.29 0.30-0.34 0.35-0.39 0.40-0.44 



Size interval (mm 3 ) 



Figure 3 



Latitudinal variation in egg size of the anchoveta (£. ringens ) along northern 

 and central Chile during the peak months of the spawning season. Y-axis is 

 frequency over the total number of eggs measured at each locality. 



of these factors co-occur. For instance, changes in growth 

 rates for yearly cohorts during the spawning season (low at 

 the beginning, fast at the end) have been documented for 

 the southernmost population (Cubillos et al., 2001). Alter- 

 natively, variations in the population age structure during 

 the spawning season have also been reported as the 1.5 

 year-old new recruits begin to spawn in early summer (late 

 December-January, Cubillos et al., 1999, 2001 ). Changes in 

 environmental factors affecting the spawning adults also 

 correlate with the egg-size variations. The photoperiod and 

 nearsurface temperatures increase as the spawning season 

 progresses from mid-winter to late spring. 



Larger egg size at the beginning of the spawning season 

 in winter may be advantageous for these offspring because 

 the chances of survival increase with the larger sizes of the 

 hatching larvae. According to Cushing (1967), larger size 

 larvae should be favored over smaller larvae in seasons 

 with variable environmental conditions. In theTalcahuano 

 area, strong fluctuations in the hydrographic regime occur 

 during winter as strong north wind storms alternate with 



short periods of south winds, and also because of the in- 

 creased river flow to the coastal zone (Castro et al., 2000). 

 Larval food, although variable, seems to be sufficient to 

 support most of the larval growth demands for larger 

 exogenous feeding larvae during winter (Hernandez and 

 Castro, 2000). For recently hatched larvae, however, the 

 picture might be slightly different because, in addition to 

 food supply variability, the strong turbulent environmental 

 conditions may jeopardize first feeding success. In these 

 highly variable areas, therefore, larger larval size at hatch- 

 ing and larger yolk reserves may be even more important 

 than in other less hydrographically variable areas and 

 seasons. 



A remarkable increase in egg size at the peak spawn- 

 ing season occurred with respect to latitude. Egg from 

 the northernmost (20°S) latitude were at a maximum 

 559c larger than eggs from the southernmost (36°S) lati- 

 tude. Latitudinal variations in egg size have been previ- 

 ously reported for other anchovies (i.e. Engraulis anchoita; 

 Ciechomski, 1973). However, egg-size variations for fishes 



