FISHERY BULLETIN: VOL. 79, NO. 1 



was seated tightly against the cable connecting 

 probe and meter. Calibration of the O2 meter was 

 checked against air-saturated seawater at the 

 start, midpoint, and end of each experimental 

 run; and the temperature readings were frequent- 

 ly verified with a mercury thermometer. As an 

 additional check on the O2 meter's accuracy, 

 readings were twice compared with Winkler de- 

 terminations. The instrument gave stable and 

 reliable readings with accuracy ±0.2 mg O2/I. 



Oxygen was supplied from standard 6,800 1 

 cylinders through fine (800 grit) 15 cm aluminum 

 oxide grinding stones (Baldwin 1970) to produce 

 minute bubbles. 



Preliminary and Control Experiments 



Preliminary experiments conducted in each 

 respirometer and subsequent work by Dizon 

 (1977) indicated that skipjack tuna demonstrate 

 no overt behavioral manifestations of stress as 

 long as O2 levels are maintained above 4.5 mg 



O2/I. We thus assumed that the fish under our 

 experimental conditions would exhibit respira- 

 tory independence between 7.0 and 5.0 mg O2/I. 

 All subsequent oxygen-uptake experiments were 

 conducted within that range. 



The preliminary experiments indicated that 

 1.5-2.0 g of fish per liter of water consumed 

 oxygen at a rate that would limit a run to <3 h, 

 which we rather arbitrarily set as about the 

 maximum time an experiment should last. 



Experimental Procedure 



The 10 series of 4 experiments each were made 

 with groups of 2-8 fish (Table 1). The basic 

 procedures for a series of experimental runs were 

 essentially the same for both respirometers. The 

 detailed procedures, herein described, are for 

 experiments with the small respirometer. 



Each series of experimental runs started be- 

 tween 0900 and 1100 h and continued through the 

 day and night, into the early hours of the follow- 



TABLE 1. — Respiration rate experiments with laboratory held skipjack tuna. Length measure is fork length. 



Fish 

 lot 



Numbef 

 of 

 fish 



Mean weight 

 and range (g) 



Mean length 

 and range (cm) 



Experi- 

 ment 



Respiration 



rate 



(mg 02/g per h) 



Mean respiration 

 rate of fish lot 



Swimming 

 speed 



(Lis) 



Mean 



swimming 



speed 



10 



8 



3,834(3,114-5,222) 58.6(53.2-68.0) 



671 (530-844) 



632 (475-805) 



36.1 (33.3-39.0) 



35.5 (31.5-38.1) 



1,719 (1,412-2,026) 44.8 (42.4-47.2) 



2,539 (2,411-2,667) 52.8 (52.7-52.8) 



1,703 (1,496-1,910) 45.1 (43.5-46.7) 



2,178 (1,890-2,467) 49.3 (47.1-51.5) 



2 2,790(2,523-3,057) 51.6(49.8-53.3) 



1,349 (1,161-1,537) 44.6 (42.4-46.7) 



2 2,200 (2,132-2,268) 50.2 (48.3-52.1) 



1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 



0.499 



0.551 



0.506 



0.522 



0.382 



0.555 



0.577 



0.658 



0.395 



0.575 



Overall means 



1,962 



46.9 



0.522 



1.1 



1.7 



1.8 



1.4 



1.2 



1.6 



1.4 



1.4 



1.3 



1.3 



1.4 



34 



