ACCLIMATION STATES OF JUVENILE STRIPED BASS 



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a: 32 



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18 20 22 



ACCLIMATION TEMPERATURE, "C 



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Fig. 3 Acclimation patterns of young-of-the-year striped bass, 

 Morone saxatilis. A least squares regression of critical thermal 

 maximum (CTMax) on constant acclimation temperatures (Y = 

 24 + 0.483X, r = 0.901, and P < 0.001). Acclimation temperatures 

 were calculated for empirically determined mean CTMax values for 

 bass held in fluctuating temperature regimes. Fluctuations were 

 computer-controlled sinusoidal curves varying ±5 C around a 20 C 

 base at a frequency of 1, 2, and 6 cycles/24 hr. 



(Arneirus nebulosus) apparently acclimated to the highest tempera- 

 ture encountered rather than to an average of the environmental 

 cycle. Fry, Hart, and Walker (1946) and Heath (1963) found a 

 similar response for brook trout (Saluelinus fontinalis) and sea-run 

 cutthroat (Salmo clarki clarki), respectively. Hubbs (1964) also 

 found similar results for young greenthroat darters (Etheostoma 

 lepidum). In contrast, striped bass in this study did not acclimate to 

 the maximum temperature of the cycle. They did not exhibit 

 greatest heat tolerance for the 24-hr thermoperiod, but tolerance 

 increased as the number of temperature cycles per day increased 

 (Fig. 3). 



Other investigators also found exceptions to the tendency for 

 temperature compensation in fishes to approximate the maximum 

 temperature of the fluctuations. Hartwell and Huish (1977) did not 

 find any significant effect of temperature cycles on the thermal 



