186 BULLETIN OF THE BUREAU OP FISHERIES 



observations on initial shock and the subsequent effects in normal and acclimatized 

 bass tested at their tolerance limits and at temperatures above these limits. The 

 following facts, which appear in Table 7, are fairly typical of what was observed in 

 all the species of animals: 



1. Acclimatization at 10° C. (50° F.), and 30° C. (86° F.) not only changed 

 the limits of tolerance of fishes but also changed their behavior at high temperatures. 



2. Acclimatization at 30° C. greatly reduced the initial shock, even at tem- 

 peratures at which many individuals eventually died. Individuals that did show 

 shock effects rarely survived. 



3. Acclimatization at 10° C. greatly increased initial shock, and large numbers 

 of individuals, after showing great disturbance of equilibrium and respiration, were 

 able to make at least a temporary recovery. 



Table 7. — Incidence of and recovery from initial shock in large-mouthed black bass; the figures in the 



table refer to percentages of individuals 



Acclimatization 



Test tem- 

 peratures, 

 °C. 



Showed no 

 shock effects 



s 



Recovered normal 

 equilibrium and 

 respiration 



howed shock effects 



Recovered normal 

 equilibrium but 

 not respiration 



No apparent 

 recovery 



Lived 



Died 



Lived 



Died 



Lived 



Died 



Lived 



Died 



Normals 



32 



0 





0 



100 



0 



0 



0 



0 



0 





34 



0 





0 



26 



0 



0 



20 



0 



54 





36 



0 





0 



0 



12 



0 



0 



0 



88 



30°, 1 day 



36 



88 





0 



12 



0 



0 



0 



0 



0 





38 



0 





17 



0 



17 



0 



0 



0 



66 



30°, 4 days 



36 



0 





0 



60 



40 



0 



0 



0 



0 





38 



0 





57 



0 



0 



0 



0 



0 



43 



10°, 1 day 



30 



100 





0 



0 



0 



0 



0 



0 



0 





32 



0 





0 



75 



0 



0 



25 



0 



0 





34 



0 





0 



0 



0 



0 



0 



0 



100 



10°, 4 days 



30 



0 





0 



100 



0 



0 



0 



0 



0 





32 



0 





0 



0 



0 



0 



83 



0 



17 





34 



0 





0 



0 



0 



0 



40 



0 



60 



10°, 16 days 



30 



0 





0 



0 



0 



0 



40 



0 



60 



The results obtained with tadpoles paralleled fairly closely those obtained with 

 fishes. While there was not the tendency to rise to the surface, which was noticed 

 in fishes, the loss of equilibrium often was very pronounced. The increase in tem- 

 porary initial shock by acclimatization at 10° C. was clearly noted, several indi- 

 viduals (fig. 7) being observed to go into heat rigor within the first few minutes of 

 a test and resume normal movement before the end of the first hour. 



The significance of the shock effects is not clear. The loss in equilibrium 

 and tendency to rise to the surface, which was noted in fishes, resembled the behavior 

 noted by Hall (1924) in fishes that were subjected to high concentration of C0 2 

 and low concentrations of oxygen. Whether the effect was due to the secretion of 

 gas into the swim bladder, or simply to the expansion by heat of the gas already 

 there, seems uncertain. In any case, the loss of equilibrium does not appear neces- 

 sarily to be closely connected with the immediate cause of death of fishes or tad- 

 poles, as death often occurred several hours after complete recovery of equilibrium. 



