504 



Fishery Bulletin 9 1 (3). 1993 



juveniles may not be as elevated or may converge on 

 adult rates more rapidly than those of captive juve- 

 niles. For example, the magnitude by which juvenile 

 metabolic rates are elevated may be a function of their 

 growth rates, which were generally much higher in 

 captivity than in free-ranging harbor seals. Alterna- 

 tively, the elevated metabolic rates of juveniles may 

 have been obscured in Boulva and McLaren's (1979) 

 analysis by the indiscriminate pooling of juveniles and 

 adults, or the average meal sizes of juveniles underes- 

 timated due to seasonal biases. For instance, most of 

 Boulva and McLaredn's ( 1979) specimens were collected 

 in summer and fall, which coincides with a post-wean- 

 ing reduction in food intake in several other species of 

 phocids (Worthy, 1987b). 



In the absence of any compelling basis for favouring 

 either FRl slv or FR2 S , X „ their mean, denoted as FR vxl , 

 was adopted in subsequent analyses. Since juvenile 

 FR1 M and FR2 s(x) differed by about ±20% of their mean, 

 and juveniles accounted for 62% of the total population 

 energy budget, this introduced a potential error of ±12% 

 into the overall population energy budget. Estimated 

 daily food requirements, FR XI>I , ranged from 1.5 kg for 

 yearlings to 2.7 kg for full grown males, which repre- 

 sented 6.3% and 3.1% of their total body masses respec- 

 tively. The mean per capita daily food requirement, FR, 

 was estimated to be 1.9 kg, or 4.3% of mean body mass. 



