FISHERY BULLETIN: VOL. 85, NO. 1 



Table 2. — Range of mean (±SD) excess muscle temperatures in paralyzed tuna. 



Tuna 



Kawakawa 



Yellowfin 



Skipjack 



20°C 



25°C 



30°C 



Mean 



SD 



Mean 



SD 



Mean 



SD 



0.7(±0.2)-1.9(±0.3) 

 0.3(±0.2)-1.4(±0.1) 

 0.2(±0.1)-0.6(±0.1) 



0.5(±0.2)-1.5(±0.3) 

 0.0(±0.1)-0.7(±0.2) 

 0.0(±0.2)-1.0(±0.2) 



^1.0(0.1) 



0.2(±0.1)-0.4(±0.1) 

 ^0.6(±0.2) 



'Only one fish survived long enough to provide useful data. 



stops all movements, all fish showed a decrease in 

 metabolic rate after injection. The decrease ranged 

 from 10 to 52% (mean 36%). 



The directly measured SMR's from four aholehole 

 and four rainbow trout paralyzed with Flaxedil are 

 given in Table 3. 



DISCUSSION 



Adequacy of Directly Measured SMR 



Muir et al. (1965) provided a regression equation 

 for SMR versus weight for aholehole adapted to 

 23 °C freshwater, based on extrapolation of swim- 

 ming speed-metabolic rate curves back to zero swim- 

 ming speed. The predicted freshwater SMR's based 

 on their regression equation was increased by 75% 

 to account for the higher osmoregulatory costs of 

 seawater adapted animals (Nordlie and Leffler 

 1975). No correction was made for temperature. As 

 shown in Table 3, in all cases but one, the directly 

 measured SMR's are close to the SMR's based Muir 

 et al.'s data when corrected for seawater adapted 

 animals. With respect to rainbow trout, in all cases 

 but one, directly measured SMR's are within one 

 standard deviation of the SMR's obtained by extra- 

 polation to zero swimming speed for rainbow trout 

 at 15°C obtained by Bushnell et al. (1984). There- 

 fore, directly measuring SMR's in Flaxedil-para- 

 lyzed aholehole and rainbow trout yields data that 

 are similar to data obtained by the more widely used 



method of determining SMR by extrapolation of a 

 swimming speed-metabolic rate curve back to zero 

 swimming speed. 



Tropical tuna species such as yellowfin, skipjack, 

 and kawakawa will survive in a swimming tunnel 

 for only short periods of time. Although other 

 methods to control svdmming speed (such as weight- 

 ing and fin clipping, Dizon and Brill 1979; Boggs 

 1984) have been tried, they have met with only 

 hmited success. Therefore, direct measurement of 

 SMR's using Flaxedil-paralyzed animals is for now 

 the only way to obtain these data for tropical tuna 

 species. As the data from aholehole and rainbow 

 trout show, direct measure of SMR's using para- 

 lyzed animals yields results similar to that obtained 

 by the more commonly used method of extrapolating 

 swimming speed-metabolic rate curves back to zero 

 swimming speed. 



The heart rates ( -i- 1 SE , at 25°C) observed in this 

 study were 230 + 20, 206 + 36, 132 + 17/min for skip- 

 jack tuna, kawakawa, and yellowfin tuna, respec- 

 tively. These heart rates are higher than those 

 observed for lightly anesthetized skipjack tuna 

 (Stevens 1972), and are 60 and 39% higher than 

 heart rates measured in skipjack and yellowfin tunas 

 (respectively) that have been immobilized by spinal 

 blockade with lidocaine and are force ventilated (un- 

 publ. obs.). The heart rates measured in Flaxedil- 

 paralyzed animals are, however, within the range 

 exhibited by free-swimming skipjack tuna (80-240 

 beats/min, Kan wisher et al. 1974). The higher heart 



Table 3. — Standard metabolic rate of aholehole and rainbow trout. 



'Based on Muiretal. (1965) and corrected for saltwater adapted fish based on Nordlie and Leffler 

 (1975). 



2From Bushnell et al. (1984), for 250-350 g fish adapted to 15°C. No corrections for the vtreight 

 dependence of Sf^R were provided. 



3SK/IR determinations made approximately 20 h apart. 



30 



