| Summary: | Critical thermal maximum (CTmax) related positively with acclimation temperature between 20.0° C and a maximum that varied with the four species; Devario acrostomus, Mystacoleucus chilopterus, Barbodes binotatus and Rasbora caudimaculata, between 30.0 and 35.0° C. Highest and lowest CTmax were 39.0±1.0° C at 35.0° C acclimation for B. binotatus and 34.6±0.5° C at 20.0° C for D. acrostomus, respectively. Thermal scope at 25.0° C acclimation was lowest at 26.8° C for D. acrostomus and, higher at 29.6, 29.7 and 30.1° C for M. chilopterus, R. caudimaculata and B. binotatus, respectively. Interestingly, the majority of tropical Thai fish and temperate species examined to date showed a similar maximum thermal tolerance from the mid to high 30s that almost certainly relates to temperature induction of HSP and their production. Global temperature increases predicted for Thai rivers and others in Southeast Asia during the latter portion of the current century are likely to exceed the thermal tolerance of many indigenous fishes with important losses in species diversity.
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