Abstract: To examine the effects of constant and diel-fluctuating temperature on thermal tolerance of zebrafish (Danio rerio) at different lifehistory stages, the newly hatched fry, juvenile fish, and sexually mature females and males were acclimated to constant temperature (28 ℃) and diel-fluctuating temperature (26-30 ℃) for two weeks. Then, the critical thermal maxima (CT_max), lethal thermal maxima (LT_max), critical thermal minima (CT_min), and lethal thermal minima (LT_min) of zebrafish at different life-history stages were measured using the critical thermal methodology of Becker and Genoway. Acclimation temperature, life-history stage, and their interactions had significant effects on thermal tolerance of zebrafish (P<0.05), whereas acclimation temperature and gender had no significant effect on thermal tolerance of adult zebrafish (P>0.05). The thermal tolerance of larvae was weaker than that of juvenile and adult fish, with lowerCT_max and LT_max and higher CT_min and LT_min. These characteristics might be related to the living habits and habitat environment of fishes at different life-history stages. The diel-fluctuating temperature had no effect on the thermal tolerance of juvenile and adult fish, but it increased body length and decreased thermal endurance scope in larvae, suggesting a tradeoff between growth and thermal tolerance.

Key words: socio-hydrology, coupled human-water system, sustainable utilization of water resources, two-way feedbacks.