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



individual. Detwyler and Houde (1970) found that 

 during the first four feeding days, bay anchovies 

 ate copepod nauplii, copepodites, and adults with 

 daily average widths in the range 50-112 ^m. 

 Because they are much easier to catch than 

 copepods, larger rotifers will be eaten. In this study, 

 growth might have been better with a diverse diet, 

 but rotifers were used because their size range is 

 limited and their nutritional quality is relatively 

 well defined. 



Energy utilization on a caloric basis was assess- 

 ed separately for endogenous (eggs, prefeeding and 

 starving larvae) and exogenous (feeding larvae) 

 nutrition. Energy budgets were constructed, based 

 on the equation 



I 



M + F&U 



in which I is ingestion, G is growth, M is metabolic 



needs, F is egestion, and U is excretion. For eggs 

 and unfed larvae, both I and F are near zero. Be- 

 cause energy is needed for embryonic growth and 

 metabolism, and some is excreted, the growth term 

 will be negative. The form 



G = I - M - F&U 



may be more appropriate to consider in the con- 

 text of growth and survival. G in calories was 

 estimated from dry weight and proximate analysis 

 data. I was estimated from feeding rate data. 

 Oxygen uptake data provided M. Egested and 

 excreted calories (F&U) were estimated by differ- 

 ence. With endogenous nutrition, G = -M - U, 

 and U = -G - M. With exogenous nutrition, 

 F&U = I - G - M. Because F and U were not 

 estimated separately, assimilation (A = I - F) is 

 not considered. 



Bay Anchovy 



I 



LU 



5 



> 

 a. 

 a 



20 40 60 80 100 120 140 160 180 200 220 240 



HOURS AFTER FFRTILIZATION 

 Figure 1.— Dry weight of bay anchovy eggs, unfed larvae, and fed larvae. 



282 



