Critical thermal maxima of selected Thai freshwater fishes

Name: Sampan Tongnunui

LCSH: Burapha University.Faculty of Science

Abstract: Critical thermal maxima (CTmax), as surrogate estimates of lethal temperatures, were measured for 32 indigenous and relatively common fishes from two small rivers in western and eastern Thailand after acclimation to 25.0 C. CTmax values were similar for all species ranging from approximately 35.1 to 38.7 C, with a mean of 37.2+-0.9 C. Currently, annual monthly maximum temperatures of some Thai rivers approach or exceed these CTmax values. CTmax measurements made earlier for freshwater temperate species acclimated to 25.0 C (n=51, 37.0+-1.7C) are almost identical to those measured in the present study for Thai fishes. Global climate change models predict ambient temperatures in Southeast Asia will increase by 3.0 to 5.0 C in the coming decades. Forecasted temperature changes are likely to impose changes in distribution, abundance and mortalities of some freshwater Thai fishes. Critical thermal maximum (CTmax) related positively with acclimation temperature between 20.0 C and a maximum that varied with the four species; Danio regina, Mystacoleucus marginatus, Systomus 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 S binotatus and 34.6+-0.5 C at 20.0 C for D. regina, respectively. Thermal scope at 25.0 C acclimation was lowest at 26.8 C for D. regina and, higher at 29.6, 29.7 and 30.1 C for M marginatus, R. caudimaculata and S. binotatus, respectively. Interestingly, the majority of tropical Thai fish and temperate species examined to data 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. CTmax values of fishes were significantly differed among wet and dry seasons of four species (p<0.05). CTmax was found lowest in May of wet season for four species; D.regina, Channa gachua, R. caudimaculata and M. marginatus were 35.1+-0.3, 36.1+-0.2, 37.1+-0.3 and 37.2+-0.3 C. While, CTmax found highest was 39.1+-0.4, 38.7+-0.4, 38.2+-0.4 and 37.3+-0.4 C for M. marginatus, R. caudimaculata, C. gachua and D. regina in February of dry season. Thermal tolerance of four species were increased approximately 2.2, 2.1, 19 and 1.6 C, from wet to dry seasons, respectively. CTmax for fish acclimatized to an ambient river temperature between 24.1 C and 27.1 C was the same as that for acclimated to these temperatures. CTmax the four species examined was significantly correlated to temperature (p<0.05). CTmax was lowest at 36.0 C for D. regina acclimated to 24.1 C and found highest, 38.6 C for M. marginatus, R. caudimaculata and S. binotatus acclimated to 27.1 C. CTmax for four species indicated that rate of fish acclimatization that maintained in the ambient river temperature cycle was rapidly exposed to temperature change about 3 C more than fish acclimation heal in constant temperature.

Burapha University. Library

Address: CHONBURI

Email: buulibrary@buu.ac.th

Name: Frederick William Henry Beamish

Role: Principal advisor

Name: Richard A Cunjak

Role: Co-advisor

Created: 2017

Modified: 2020-08-03

Issued: 2020-08-03

วิทยานิพนธ์/Thesis

application/pdf

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degree

Descipline: Environmental Science

Grantor: Burapha University

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