ABSTRACT
Critical thermal maximum (CTM), lethal thermal tolerance (LT), and oxygen consumption rates (mg O2/g fish/min)
of juvenile southern flounder (average weight 5.5 g) were determined for acclimation temperatures (AT) of 13, 17, 21,
25, and 29 C. A total of 75 fish were used to measure CTM and LT in salinities of 0, 12, and 34 ppt. Three replicates of
two fish each were used to measure oxygen consumption rates in 34 ppt. Salinity had a significant effect on both CTM
and LT (P<0.05). The mean CTM for 0 ppt was 0.46 C lower than the mean CTM for 12 ppt and 0.84 C lower than the
mean for 34 ppt. The mean LT for 0 ppt was 0.40 C lower than the mean LT for 12 ppt and 0.61 C lower than the mean

for 34 ppt. The LT was 20.39 C higher than acclimation temperature at 13 C but only 9.85 C higher at 29 C. The highest
LT was 38.85 C for fish acclimated to 29 C. The oxygen consumption rate increased from 1.26 to 4.53 mg O2/g fish/min
as temperature increased from 13 to 29 C. The highest Q10 values, for oxygen consumption, occurred between 21 C and
25 C. Between 13 C and 17 C the Q10 was 2.37, between 17 C and 21 C the Q10 was 2.50, between 21 C and 25 C the Q10
was 2.68, and between 25 C and 29 C the Q10 was 1.29. Based on the relationship between LT and preferred temperature,
and the observed decline in Q10 for oxygen consumption, we calculated that the final preferred temperature (FP) for
juvenile southern flounder is between 25 C and 29 C in salinities from 0 to 34 ppt.

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