524 
Fishery Bulletin 11 5(4) 
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Summer 02 
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Winter 01 
Winter 02 
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Mean egg volume 
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Salinity 
Figure 5 
Temperature-salinity diagrams with mean volume of eggs (mm 3 ) of Argentine anchoita 
(Engraulis anchoita) per station in the southeastern Brazilian Bight sampled with ieh- 
thyoplankton tows during summer and winter of 2001 and 2002. Temperature and salin¬ 
ity were measured in situ at 10-m depth; TW=Tropieal Water; SACW=8outh Atlantic 
Coastal Water; CW=Coastal Water. 
Regional variation in eggs A total of 73,104 eggs of 
Engraulidae were collected. Argentine anchoita eggs 
represented 80.5% of all engraulid eggs sampled 
(n=58,826). They were sampled throughout the SBB, 
and their spatial horizontal distribution varied from 
one year to another (Fig. 7). Eggs of Argentine anchoi¬ 
ta were collected over a wide range of temperatures 
and salinities in each area (Fig. 8). 
A total of 8809 eggs of Argentine anchoita that were 
collected during the summer over 5 years and in all 3 
areas were measured (Table 5). In a comparison of only 
areas 1 and 3, it was observed that, in general, eggs in 
area 3 were larger than eggs in area 1, with the excep¬ 
tion of January 1988 when the opposite was found to 
be true. No size pattern was observed for eggs collected 
in area 2; egg sizes from this area were usually in be¬ 
tween those of areas 1 and 3 and showed no significant 
differences in size when compared with eggs from other 
areas. During December of 1991 and January of 1993, 
eggs from area 2 were the largest sizes throughout the 
time period (Table 5, Fig. 8). 
Discussion 
Egg size varies among species and among populations 
because of temporal, biological, spatial, or environmen¬ 
tal factors (or a combination of these factors). Within 
a species, planktonic egg size decreases as the spawn¬ 
ing season progresses (Bagenal, 1971; Chambers and 
Waiwood, 1996). For species of Clupeiformes, this de¬ 
crease in the egg size may be due to a reduction in 
maternal energy reserves over the spawning season, 
a switch in the stored energy from reproduction to 
