FISHERY BULLETIN: VOL. 78, NO. 3 



larvae compared at hatching. Yolk-sac volumes, 

 however, differed significantly. Larvae reared at 

 12° and 4° C had significantly larger yolk volumes 

 than those reared at 8° and 10° C (ANOVA, SNK, 

 P<0.05). Larval tissue weight is taken as the dif- 

 ference between ash-free dry weight of the entire 

 yolk-sac larva and ash-free dry weight of yolk. 

 Since total ash-free dry weight was not signifi- 

 cantly different between the four temperatures, it 

 follows that the ash-free dry weight of the larval 

 tissue alone must be significantly greater in those 

 larvae reared at 8° and 10° C. This coincides with 

 the difference seen in length. At yolk-sac absorp- 

 tion there were no significant differences either in 

 length or ash-free dry weight of yolk-sac larvae 

 (ANOVA, P>0.05) for the three temperatures 

 where these variables were measured. 



Notochord length increased with time after hatch- 

 ing (Table 3). Analysis of covariance revealed 

 that larvae incubated at 12° C grew significantly 

 faster than those at the other temperatures 



(P<0.05). Larvae at 4° C grew at an interme- 

 diate rate that was significantly different (P<0. 05) 

 from fish in other treatments. No significant 

 difference (P>0.05) in growth rate was evident 

 between 8° and 10° C larvae. Fish in both of 

 these treatments exhibited the slowest growth 

 rates (P<0.05). Regression coefficients of ash-free 

 dry-weight of yolk-sac larvae and yolk-sac vol- 

 umes vs. hours posthatch were significantly 

 different (P<0.001) from zero (Table 3). 



Ash-free dry weight of the larva minus its yolk 

 sac at a particular temperature and time was cal- 

 culated as the difference between the predicted 

 total ash-free dry weight and the predicted ash- 

 free dry weight of the yolk (Tables 4-7). Predicted 

 values indicate that embryo weight increases 

 linearly with time at all temperatures except 8° C 

 (Table 5) where it remains constant. 



Temperature effects on yolk utilization rate 

 were examined by comparing the regression coef- 

 ficients of the four equations for decrease in yolk- 



TabLE 3. — Predictive linear equations (Y = a + bX) derived from least squares linear fits of the yellowtail 

 flounder data. All equations are based on measurements taken every 24 h between hatching and yolk-sac 

 absorption. AFDW = ash-free dry weight, and In = natural logarithm. 



Variables Y vs X and temperature (° C) 



Sample 

 size 



95% confidence 

 limit for a 



95% confidence 

 limit for ti 



and calculated efficiencies at 4° C. AFDW = ash-free dry weight. 



Hours 

 posthatch 



Yolk-sac larvae 

 (mg AFDW) 



Yolk-sac volume 

 (mm^) 



Yolk' 

 (mg AFDW) 



Larval tissue^ 

 (mgAFDW) 



Yolk utilized^ 

 (mg AFDW) 



Efficiency* 



734 



