44 



Fishery Bulletin 94( 



1996 



barred sand bass and fantail sole eggs than for white 

 croaker and California halibut eggs. For both bass 

 and sole, optic vesicles and somites (stages O and S) 

 were visible in the embryo by the time of blastopore 

 closure, stage VI (Table 2, Figs. 1 and 2). Embryonic 

 development of bass was particularly rapid; the em- 

 bryonic axis was evident by the time the germ ring 

 enclosed half the yolk mass. In contrast, for both 

 croaker and halibut the embryonic axis was visible 



2 6 10 14 18 22 26 30 34 38 42 46 50 54 58 62 66 70 74 



Hours after fertilization 



Figure 2 



Development of eggs of fantail sole, Xystreurys liolepis, at three 

 temperatures. Eggs died at 8°, 12°, and 28°C during stage II. De- 

 scriptions of egg stages are presented in Table 2. 



VII 



s - 



0-- 



2 6 10 14 18 22 26 30 34 38 42 46 50 54 58 62 66 70 74 

 Hours after fertilization 



Figure 3 



Development of eggs of white croaker, Genyonemus lineatus, at 

 three temperatures. Eggs died at 8"C during stage I and at 24"C 

 with no cell division evident. Descriptions of egg stages are pre- 

 sented in Table 2. 



just prior to blastopore closure, and optic vesicles and 

 somites appeared after closure (Figs. 3 and 4). 



Eggs of barred sand bass hatched at a wider range 

 of temperatures, 12-28°C, than did those of the other 

 three species. However, at 12°C bass eggs took much 

 longer to hatch (94 hours) than at higher tempera- 

 tures, and many sampled eggs were dead (Fig. 1). 

 Bass larvae that hatched at 12°C appeared to be ab- 

 normally developed, swam weakly, and soon died. 

 Thus, successful hatching of viable embryos 

 occurred only at 16-28°C for barred sand bass. 

 Fantail sole eggs hatched at 16-24°C (Fig. 2), 

 whereas both white croaker and California hali- 

 but eggs hatched at a lower temperature range, 

 12-20°C (Figs. 3 and 4). Although not quanti- 

 fied, in each treatment most eggs that remained 

 after sampling hatched and all larvae in the 

 samples (except barred sand bass at 12°C) ap- 

 peared normal and viable. At temperatures 

 where hatching did not occur (8°C for sand bass; 

 8°, 12° and 28°C for fantail sole; and 8° and 24°C 

 for both white croaker and California halibut), 

 eggs died with little development, reaching at 

 most stage II. 



Within survival ranges, eggs of all species 

 developed faster at higher temperatures (Figs. 

 1-4). The relationship between age and stage 

 was best fitted by a linear function (Age=p stage; 

 r 2 >0.95; Table 3). One-way AN OVA was used to 

 test effects of species and temperature on rate 

 of development (fi); we could not test interac- 

 tions between species and temperature with a 

 two-way ANOVA because of missing values due 

 to egg mortalities at temperature extremes. 

 Species had no effect on rate of development (one- 

 way ANOVA, F 3 10 =0.20; P=0.89). Pooling across 

 species showed that temperature had a strong 

 effect on rate of development (one-way ANOVA, 

 F 4 9 =33.72; P<0.001). A multiple-range analysis 

 ( the Tukey test) for the temperature effect showed 

 rates of development at 12°, 16°, and 20°C to be 

 significantly different (P<0.05; Table 3). 



Because developmental rate at a specific tem- 

 perature did not significantly differ between 

 species, we examined the general relationship 

 between temperature and age at hatching by pool- 

 ing data from all species (Fig. 5). This relation- 

 ship was best fit by an exponential function: 



LniAge) = 5.395 - 0.090 (T), [r-'=0.94, n = 14\ 



where Age is the time in hours from fertiliza- 

 tion to hatching and T is the incubation tem- 

 perature (°C). Similarly, equations derived for 

 each species to determine egg age at stage and 



