ON THE STANDARD METABOLIC RATES OF TROPICAL TUNAS, 



INCLUDING THE EFFECT OF BODY SIZE AND 



ACUTE TEMPERATURE CHANGE 



Richard W. Brilli 



ABSTRACT 



The standard metabolic rates (SMR's) of fishes and the effect of body weight on SMR's are important 

 input parameters to energetics, growth, and population models. This study was undertaken to obtain 

 these data for the tropical tuna species, yellowfin tuna, Thunnus albacares, and kawakawa, Euthynnus 

 affinis. These data compliment similar SMR measurements from skipjack tuna, Katsuwonus pelamis, 

 previously published. The effect of acute temperature change on the SMR of all three species was also 

 determined. 



The SMR was estimated by directly measuring the oxygen uptake rate of animals paralyzed with 

 a neuromuscular blocking drug, rather than by the more commonly used method of extrapolation of swim- 

 ming speed-metabolic rate curves back to zero swimming speed. To test the adequacy of this technique, 

 the SMR's of aholehole, Kuhlia sandvicensis. and rainbow trout, Salmo gairdnerii, were determined 

 using similar methodology. The SMR's measured in this way were not significantly different from the 

 published SMR's of these species determined by extrapolation of swimming speed-metabolic rate curves 

 back to zero swimming speed. 



All three tuna species have very high SMR's, over five times higher than other active teleost species 

 such as salmon and trout. The effect of body size on the SMR is similar in all three tuna species, but 

 the weight specific SMR of tuna decreases more rapidly with increasing body size than in other fishes. 

 Based on SMR's measured at 20° and 25°C, the Qjo's were 3.16, 2.31, and 2.44 for yellowfin tuna, 

 kawakawa, and skipjack tuna, respectively. These are similar to Qig values found for the SMR's of other 

 teleosts. 



Tunas can achieve exceptionally high maximum aerobic metabolic rates. This ability requires a com- 

 plete set of anatomical, physiological, and biochemical adaptations. I hypothesize that one of these adap- 

 tations, large gill surface areas, causes tunas to have exceptionally high energy demands even at rest. 

 Tunas' high SMR's are an inevitable consequence of their ability to achieve exceptionally high maximum 

 aerobic metabolic rates. 



The standard metabolic rate (SMR) (the metabohc 

 rate of a postabsorptive animal completely at rest) 

 and the effect of body size on SMR are important 

 input parameters to growth, energetics, and popula- 

 tion models (e.g., Sharp and Francis 1976; Kitchell 

 et al. 1978). This study was therefore undertaken 

 to obtain these data for yellowfin tuna, Thunnus 

 albacares, and kawakawa, Euthynnus affinis. These 

 measurements were designed to directly compli- 

 ment the SMR measurements for skipjack tuna, 

 Katsuwonus pelamis, that had been previously pub- 

 lished (Brill 1979). The effect of acute temperature 

 change on the SMR of skipjack tuna, yellowfin tuna, 

 and kawakawa was also determined. The effect of 

 acute temperature change, as opposed to the effect 

 of temperature adaptation, is relevant to tuna be- 

 cause of the 5° to 15°C water temperature changes 



'Southwest Fisheries Center Honolulu Laboratory, National 

 Marine Fisheries Service, NOAA, 2570 Dole Street, Honolulu, HI 

 96822-2396. 



Manuscript accepted November 1986. 

 FISHERY BULLETIN: VOL. 85, NO. 1, 1987. 



these species normally experience during the daily 

 vertical movements which are a constant feature of 

 their behavior in the open ocean (Dizon et al. 1978; 

 Carey and Olson 1982; Yonemori 1982). 



In other teleosts, SMR's have been determined 

 by extrapolating metabolic rate-swimming speed 

 curves back to zero swimming speed (e.g., Brett 

 1965). Although Graham and Laurs (1982) have suc- 

 cessfully measured the metabolic rate of albacore, 

 T. alalunga, (a temperate tuna species) swimming 

 in a water tunnel, this methodology is presently not 

 possible with tropical tunas (skipjack tuna, yellow- 

 fin tuna, and kawakawa). Attempts to get these 

 species to swim in several prototype water tunnel 

 designs have shown that they will do so for only very 

 short periods (Brill and Dizon 1979 and unpublished 

 observations). As a result, measuring the SMR's of 

 tropical tunas directly in animals paralyzed with a 

 neuromuscular blocking agent is currently the only 

 method available to obtain these data. 



To validate this technique, the SMR's of rainbow 



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