54 



Fishery Bulletin 94( 



1996 



BO 



„ 60 



£ 40 



100 n" 



20 



- 

 10|- 



_] I I I I 1 I I 



Age (yr) 



Figure 3 



Changes with age of cumulative energy utilized for growth (G) and 

 metabolism (A/Ktop), age-specific net growth efficiency (/f,)(middle); 

 and daily ration (F'Mbottom) for Maurolicus muelleri. For M, K. 2 , 

 and F\ solid line represents size-independent metabolism, and bro- 

 ken line size-dependent metabolism. 



Discussion 



The decrease of specific oxygen consumption 

 rates (R/WW) with the increase of body size is a 

 widespread phenomenon in animals (Zeuthen, 

 1953; Hemmingsen, 1960) but is often masked 

 by narrow size coverage and the scatter of data 

 (Hemmingsen, 1960). From this view, R/WW 

 independent of size of specimens obtained in this 

 study may be an artifact due to incomplete cov- 

 erage of the entire body-size range of M. muelleri 

 (specimens less than 57mg WW or 20 mm TL 

 were not used in the ETS assay). If a general 

 body weight exponent of v = 0.85 given for fishes 

 (Winberg, 1956; modified by Ricker, 1973) is 

 adopted, R = 0.534 WW 85 is obtained from the 

 same ETS assay data (cf. Fig. 1). In the present 

 study, differences in the energy budget calcula- 

 tions due to the use of size-dependent M, in- 

 stead of size-independent M, were also exam- 

 ined (Fig. 3; Table 4). 



The differences due to the use of size-depen- 

 dent M, instead of size-independent M, were 

 most pronounced at younger stages, in which 

 the size-dependent M yielded lower age-specific 

 K., and higher age-specific F' ( Fig. 3 ). However, 

 choice of size-independent M or size-dependent 

 M had little effect on the results of lifetime av- 

 erages of K 2 ( 16.7% vs. 18.5%) and F' (2.9% vs. 

 2.6% KTable 4 ). The choice of size-dependent M, 

 instead of size-independent M, again had little 

 effect on calculations of the fraction of energy 

 stored in gonads (the former added only 0.1% 

 to figures derived from size-independent M). 



Information about metabolic rate of micro- 

 nektonic fishes is currently limited. Whole-ani- 

 mal respirometry data of typical epipelagic fish 

 were obtained by Lasker (1970), who success- 

 fully maintained Pacific sardine {Sardinops 

 caerulea) in the laboratory and measured 



