A comprehensive understanding of thermal tolerance in Percocypris pingi (Tchang, 1930) under different acclimation temperatures supported by behavioral assessments

Abstract

This study assessed the thermal limits of Percocypris pingi, initially reared at 9.86 °C. Fish were short-term acclimated to 12 °C, 18 °C, and 24 °C for two weeks, and their CT_max and CT_min were determined. A separate group underwent long-term acclimation in outdoor conditions, where water temperatures averaged 2.66 °C higher than the species' natural habitat. In September, when temperatures reached 28.91 °C, their CT_max was re-evaluated. Behavioral indicators—swimming speed, shoal cohesion, and temperature preference—were used to support thermal tolerance assessments. Our findings indicate that P. pingi exhibits a narrow thermal tolerance range. Specifically, fish acclimated at 12 °C, 18 °C, 24 °C and long-term acclimation of 28.91 °C showed CT_max values of 33.11 °C, 34.26 °C, 34.55 °C and 35.01 °C. Although CT_max increases only slightly with higher acclimation temperatures, recovery after the CT_max measurement was significantly impaired in the group acclimated at 24 °C for a short term. Only 13.33 % of individuals recovered within 30 min compared to 100 % in other groups. Behavioral analyses showed stable swimming speeds near CT_max in the 18 °C and 24 °C groups, but heightened activity in the 12 °C group. Additionally, shoaling behavior became more dispersed during CT_max testing. Temperature preference tests indicated a consistent inclination toward cooler zones (12–18 °C), suggesting that P. pingi may actively seek thermal refuges in natural environments to mitigate thermal stress. Habitat temperatures (19.5–27.6 °C) remain below the species’ thermal tolerance (>33 °C), according to WorldClim data. Our temperature and behavioral data provide a reliable assessment of thermal risks for P. pingi and offer guidance for its conservation under climate change.