FISHERY BULLETIN: VOL. 87. NO. 2. 1989 



to 12/h on feeding day 4, and then rose to 35/h on 

 feeding day 8. 



Average daily ration was slightly higher for 

 anchovies than for sea bass. For the 168 hours 

 after first feeding, anchovy daily ration averaged 

 138% by weight and 126% by calories, compared 

 to 126% by weight and 122% by calories for sea 

 bass. 



Energy Budgets 



Total energy ingested during the 168 h period was 

 0.665 cal by bay anchovies and 1.191 cal by black 

 sea bass (Tables 5, 6). Gross growth efficiency (Kj, 

 G/I) and metaboHc component (M/I) changed with 

 age of larvae. Anchovy G/I increased from - 18% 

 to 15% (overall 9%), while sea bass G/I rose from 

 9% to 19% then dropped to 12% (overall 14%). Per- 

 cent of ingested energy used for metabolism by 

 anchovies (M/I) decreased from 44% to 21% (over- 

 all 24%), while sea bass M/I increased from 16% 

 to 37% then dropped to 30% (overall 28%). Over- 

 all F&U/I was 67% for anchovies and 58% for sea 

 bass. 



Four-Day Energy Budgets 



A striking difference in early growth capability 

 is revealed by restricting the energy budget to the 

 first 96 hours after first feeding. Black sea bass in- 

 gested 1.8 times as much energy as bay anchovies, 

 0.543 vs. 0.299 cal. Egested and excreted compo- 

 nents (F&U/I = 63% and 68%) were similar. Sea 

 bass metabolic component was slightly lower (M/I 

 = 24% vs. 27%) and gross growth efficiency was 

 higher than that of anchovies (G/I = 13% vs. 5%). 



DISCUSSION 



Length of the interval between first feeding and 

 yolk exhaustion is an important factor affecting sur- 

 vivability of fish larvae because it is the period of 

 transition from endogenous to exogenous feeding. 

 Bay anchovies first feed only 8 hours before their 

 yolk is exhausted, and they do not have positive 

 growth until after EYS. Like Pacific sardines, Sar- 

 dinoips caerulea (Lasker 1962), bay anchovies may 

 be particularly vulnerable to food shortages at first 

 feeding. In contrast, black sea bass have 2 days of 



Table 5. — Energy budget for bay anchovy eggs and larvae during growth and starvation. In the first column, 

 developmental events are indicated in parentheses. G, M, and F&U as percentages of I are given in parentheses. 



Age: (rom fertilization 



Weight: measured 



Weight change: (rom column 2. 



Body calories = (weight) (estimated caloric content). 



G = Growth calories = change in body calories. 



I = Food calories = (average feeding rate) (feeding time) (0 000787 cal/rotifer). 



M = Metabolic calories (measured ^L 02/h) (0 00425 cal/^L O2) (38 hours). 



F&U = Egested and excreted calories = t - M - G. 



288 



