BRILL: STANDARD METABOLIC RATES OF TROPICAL TUNAS 



SMR and body weight in skipjack tuna is (Brill 

 1979) 



SMR = 412.0 (±27.1) W"0.563(±o.07) 

 n = 33. 



The SMR is in mg O^/h and W is body weight in 

 kilograms. The values in parentheses are the stan- 

 dard errors of the parameters. 



Effects of Acute Temperature Change 



on SMR, Heart Rate, and 



Excess Red Muscle Temperature 



A total of 8 kawakawa, 12 yellowfin tuna, and 5 

 skipjack tuna were subjected to 5°C temperature 

 changes. Most temperature changes were made 

 between 20°C and 25°C, which all fish survived. Ten 

 fish were exposed to 25° and 30°C, but only four 

 survived long enough at 30°C to provide usable data. 

 Because of the expense and difficulty in obtaining 

 live tunas, the latter treatment was not pursued. 



The SMR's and mean heart rates at 20°, 25°, and 

 30°C are given in Table 1. The Qio's of SMR for 

 water temperatures changes from 20° to 25°C were 

 variable and ranged from 5.82 to 1.39. The mean 

 Qio's (±95% confidence intervals) were 2.44 ± 

 0.97, 2.31 ± 0.51, and 3.16 ± 0.93 for skipjack tuna, 

 yellowfin tuna, and kawakawa, respectively. 



The range of mean excess red muscle tempera- 

 tures are given in Table 2. These excess muscle 

 temperatures are lower than those measured in free 

 swimming yellowfin and skipjack tunas (Dizon and 

 Brill 1979). This is as expected because in paralyzed 

 tunas, most of the heat production (i.e., energy con- 

 sumption) most likely occurs at the heart and gills 

 where the heat would not be retained by the vascular 

 countercurrent heat exchangers. 



The SMR of Aholehole and 

 Rainbow Trout 



Aholehole, unlike rainbow trout, will not sit quietly 

 in a darkened respirometer box nor stop breathing 

 movements when force-ventilated. Because Flaxedil 



Table 1. — Effect of temperature on the standard metabolic rate and heart rate of yellowfin tuna, kawakawa, and skipjack tuna. 



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