326 



Fishery Bulletin 104(3) 



(b) at each temperature were not significantly differ- 

 ent (likelihood ratio test, x| = 3.2, P=0.20; ANCOVA, 

 logmassxtemperature interaction, F,, 5y=0.81, P=0.45). 

 The mean SMR Qj^'s were 3.2 ±0.4 for 18-24°C 

 {n=U), 2.5 ±0.2 for 24-28°C (n=16), and 2.9 ±0.2 for 

 18-28°C (?! = 13). There was no overall effect of body 



Fg 59=20.99, P<0. 001). However, the allometric exponents mass on SMR QmS (increases in metabolic rate with 



temperature) (ANCOVA, mass, F^ 36=0.04, P=0.84), but 

 there was a significant negative correlation between 

 mass and SMR Qj^, for 24-28°C (P=0.014, r- = 0.36; 

 slope = -0.20 ±0.07). The temperature range did not 

 affect mean SMR Qj,, (ANCOVA, range, ^2,36 = 1-37, 

 P=0.27). The data sets were therefore pooled and the 

 overall mean Q,,, was 2.9 ±0.2 (7i=43). 



Heart rates 



Heart rate was negatively correlated with body mass at 

 all temperatures (ANCOVA, mass, Fj ^,,,=29.99, P<0.001) 

 (Fig. 2). The relationships between heart rate and body 

 mass at each of the three temperatures were 



4 6 



Mass (kg) 



Figure 2 



Heart rates (beats/min) of juvenile sandbar sharks 

 (Carcharhinus plumbeus) (treated with pancuronium 

 bromide) measured during standard metabolic rate 

 experiments at 18°C (D), 24°C (O), and 28"C (T). Solid 

 lines represent best-fit linear regressions at each tem- 

 perature as a function of body mass. Error bars indicate 

 ±1 standard error. 



0.91 



3 4 56789 10 

 Mass (kg) 



Figure 3 



Paired routine (RMR,0) and standard metabolic rates 

 (SMR,n) (mg 0._,/hl of 1.5 juvenile sandbar sharks {Car- 

 charhinus plumbeus) at 24-26 C. Error bars indicate ±1 

 standard error. The solid line depicts the best-fitting 

 allometric equation with the fish swimming in a curved 

 path in an annular respirometer: RMR = 213 (±38) 

 3^0 79(±o 111 -pjjg dashed line represents the best-fit allo- 

 metric equation using the corrected straight-line swim- 

 ming (RMRj,) estimates: RMR^, = 200 (±33) M"'"''" •". 



18°C: Heart rate = 



39.3 (±2.0) - 

 1.07 (±0.49) xM 



24°C: Heart rate = 



66.7 (±1.6) - 



1.81 (±0.30) xM 



28°C: Heart rate = 



80.4 (±2.9) - 

 2.02 (±0.61) X M. 



n = U,P=0.05,r^=0.29 (4) 



/? = 29, P<0.001, r- = 0.58 (5) 



« = 13, P=0.01, r- = 0.50 (6) 



Heart rate increased with temperature for each indi- 

 vidual and overall (ANCOVA, temperature, F.^ 5o = 64.21, 

 P<0.001) (Fig. 2). However, the influence of body mass on 

 heart rate did not vary among temperatures (ANCOVA, 

 massxtemperature interaction, F,, gij = 0.69, P=0.51). 



The mean QjqS for heart rate were 2.2 ±0.05 for 

 18-24°C (n=U). 1.8 ±0.04 for 24-28°C (/j=12), and 2.1 

 ±0.03 for 18-28°C («=11). Heart rate Q^g was not cor- 

 related with body mass (ANCOVA, mass, Pj 3, = 0.95, 

 P=0.34). However, an overall significant effect of temper- 

 ature range on heart rate Qjg was observed (ANCOVA, 

 range, F„ .„= 4.68, P=0.02). 18-24°C and 18-28°C were 

 significantly different from 24-28°C (P<0.001), but not 

 from each other (P=0.08, Tukey unequal n HSD test). 



Routine metabolic rates 



Routine metabolic rate increased with increasing body 

 mass (Fig. 3). The best-fitting allometric equation relating 

 RMR (mg Og/h) to mass (range 1.025-7.170 kg) was 



RMR = 213 (± 38) xAfO'S'^^on' 



71 = 16 (53 trials), (7) 

 r2=0.82 



The estimated additional costs of swimming in a curved 

 path versus a straight line increased with body mass 

 (range 0.8-19.9%; Fig. 3). With the straight-line swim- 

 ming (RMR^,) estimates, the allometric equation for 

 RMR became: 



RMR, = 200 (±33) x A/o" 



71 = 16, 7-2 = 0.83 



(8) 



Although the acclimation periods in the annular res- 

 pirometer were relatively short, it has been shown that 



