FISHERY BULLETIN. VOL, 76, NO. 3 



35 



30 



iij 



Q. 



2 



25 



20 



15 



10 15 



WEIGHT OF SKIPJACK TUNA (kg) 



20 



FIGL'RE lb. — Maximum tolerable water temperature for skipjack tuna as a function of size for the same two rates of metabolic activity 

 illustrated in Figure la. Based on calculated internal temperature excesses and the assumption that damage to red muscle tissue occurs 

 above 35 "C. 



200 



la'CU-SSml/LOg-i — «— I8°C^"^ 



-3.5ml/L02- 



-I8°C- 



5° S 



200 



Figure 2. — Upper panel: Temperature and dissolved oxygen (selected isopleths only) along long. 119' W, eastern Pacific Ocean, 

 August 1967 (Love 1972). Lower limits of the skipjack tuna habitat are assumed to be either 18° C or 3.5 ml/1 dissolved oxygen, as 

 indicated. The hatched layer should be warm enough for these fish, but oxygen deficient. Lower panel: Hypothesized habitat layers for 

 skipjack tuna of two sizes, 4 kg ( entire hatched area ) and 9 kg ( cross hatched area only) in the same section. Fish <4 kg could presumably 

 live anywhere between the sea surface and the lower limits, 18°C or 3.5 ml/1 of dissolved oxygen. 



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