Edwards: Allometry of energetics parameters in Stenella attenuata 



433 



METABOLIC 



20 40 60 80 100 



WET WEIGHT (kg) 



Figure 3 



Relationship between wetted and metabolic surface areas, and 



total wet weight of body in kilograms for 35 specimens of spotted 

 dolphin (.Stenella attenuata) from the eastern tropical Pacific Ocean, 

 both sexes and all ages (sizes) represented. Lines through points 

 are fitted regressions. 



WSA h , WSA fp , WSA d , WSA/i, Figs. 3 and 4). Weak 

 trends were found for energy densities of blubber 

 and muscle (ED hh ED m ; Fig. 9). Intermediate trends 

 represented the majority of the relationships ( 16 

 of 25) and included D mas (Fig. 2), all measures of 

 MCD (Fig. 5), CL (Fig. 6), BD„ (Fig. 7), F (Fig. 8, A 

 and B), %H 2 0„ and %H 2 6 „ (Fig. 10), and ED an 

 (Fig. 11). 



Parameters that exhibited strong trends dem- 

 onstrated large changes in parameter values 

 throughout the weight range studied. Although the 

 allometric effect decreased somewhat with increas- 

 ing size, parameter estimates were 300-400% 

 larger for 30-kg than for 5-kg dolphins (compared 

 with a difference of 600% (30 kg/5 kg* 100) in wet 

 weight), and 50%-85% larger for 70-kg than for 

 30-kg dolphins (compared with a difference of 233% 

 in wet weight; Table 4). 



Parameters showing intermediate trends 

 changed rapidly only from birth through the first 

 2-3 years of life (5-30 kg; Perrin et al., 1976; Hohn 

 and Hammond, 1985). Parameter values changed 

 much more slowly with size in older (larger) dol- 

 phins (30-70 kg) than in smaller dolphins (e.g., 

 less than 30 kg). For example, estimated muscle 

 fraction of body wet mass increased by 33% from 

 5-kg to 30-kg dolphins, but only by 14% from 30 to 

 70kg wet weight (Table 4). Parameter estimates 

 for these intermediate effects differed from 10% to 

 70% between 5- and 30-kg dolphins, but only from 

 5% to 30% between 30- versus 70-kg dolphins 

 (Table 4). 



Parameter values showing weak trends changed 

 little with increasing size. For example, estimated 

 ED„, increased only 8% in animals 5 kg to 30 kg in 

 weight, and only an additional 4% from animals 

 30 kg to 70 kg in weight (Table 4). The lack of any 

 significant trend in ED h „ may be due to small sample 

 size (n = 5 animals) but the relatively small scatter 

 of the existing points indicates that the apparent 

 absence of trend is probably real (Fig. 9). The lack 

 of trend in H 2 0„, also appears real, as sample size 

 was reasonably large (n = 10) and scatter about the 

 regression line relatively small (Fig. 10). 



cant trend was found for %H 2 0„, (Fig, 10) or ED hn 

 (Fig. 9). No trends were isometric (linear) in the 

 untransformed variables. Trends fell into three gen- 

 eral groups based on the strength of the relationship 

 between parameter value and wet weight (Table 4). 

 Expressed in terms of the regression coefficient (6), 

 these relationship groups were strong (0.49 < b < 0.73), 

 intermediate (-0.29 < b < -0.14 or 0.16 < b < 0.30), 

 and weak (-0.14 < b < 0.16). Strong trends were found 

 for all five of the surface area measurements (MSA h , 



Discussion 



Estimates for individual dolphins 



The practical importance of any allometric trend in 

 any particular parameter will depend not only on the 

 strength of the trend, but also on that parameter's 

 relative contribution to the energy flux being estimated. 

 This contribution is affected by the algebraic place- 

 ment of the parameter in the energy flux calculation, 



