YAMASHITA and BAILEY: BIOENERGETICS OF LARVAL WALLEYE POLLOCK 



The metabolic mass exponents, particularly for 

 routine metabolism, were close to unity. 



For prefeeding larvae, weight-specific O2 con- 

 sumption rate (|xL/h/mg) increased with age 

 (Table 3). This is probably associated with in- 

 creasing somatic tissue, because yolk is thought 

 to be nonrespiring (Rombough 1988). Weight- 

 specific rates, using yolk-free dry weight, de- 

 creased with age. As the eye became functional, 

 at days 5 and 6, a rapid rise in routine metabo- 

 lism followed the increase in light-stimulated ac- 

 tivity. From days 6 to 23 there were no signifi- 

 cant trends in the dry weight specific O2 

 consumption rate with age for any treatments 

 (ANOVA with regression, P > 0.1). 



By difference {M,.„ - M,.e), lights-on gen- 

 erated activity of feeding larvae accounted for an 

 average O2 consumption of 0.67 |xL/h/mg. Night- 

 time SDA (Mf„ - Mre) accounted for 0.47 

 ^.L/h/mg, and feeding activity associated with 

 hunting and capture of prey (M„ - M,.„ - 0.47 - 

 0.67) accounted for 0.22 jjiL/h/mg. Given that the 

 active-feeding metabolic rate was probably un- 

 derestimated by our technique as noted pre- 

 viously, and that the active metabolic rate can be 

 estimated as 2 x Mro = 4.56 ixL/h/mg, the above 



increment for active metaboHsm would be 1.81 

 IxL/h/mg. 



Energy Budget 



Energy budget components and efficiencies 

 are given in Table 4. Gross growth efficiency 

 iG/I X 100) ranged from 13.2 to 34.5% for high 

 ration and from 9.1 to 32.6% for low ration 

 larvae. The relationship of G/I and age was a 

 U-shaped function with low efficiency in middle 

 stages (Fig. 2). The ratio of metabolizable 

 energy to ingestion ((G + M)/I x 100) is termed 

 net assimilation efficiency. Net assimilation effi- 

 ciency also showed a U-shaped relationship with 

 age, ranging from 30.5 to 58.4% and from 24.4 to 

 63.5% for high ration and low ration larvae, re- 

 spectively. The ratio of the growth component to 

 metabolizable energy (G/{G + M) x 100) gradu- 

 ally increased from 40-42% at day 7 to 55-59% at 

 day 21. 



DISCUSSION 



The growth rates of walleye pollock larvae in 

 our experiments compared favorably to those of 



Table 4. — Daily energy budget components and efficiencies of larval walleye pollock. H and L indicate fiighi ration and 



low ration levels, respectively. 



'Larval dry weight was converted to calories by a factor of 5 077 cal mg V 

 ^Rotifer dry weight was converted to calories by a factor of 4 4 cal mg V 

 'Daily growth was calculated using the relative rate of growth {K) at each day interval. 

 ^Oxygen volume was converted to calories by a factor of 4 63 cal mL ' O2. 

 ^Efficiencies were expressed on caloric basis. 



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