Spatial-temporal analysis of water temperatures during spring in Lake Erhai, China: implications for fisheries

Abstract

Lake Erhai is located in a low latitude, high altitude region in Yunnan province, China, and contains diverse endemic aquatic organisms. This study provides baseline information on the spatiotemporal water temperature distribution for examining the thermal environment for aquatic organisms in Lake Erhai. Temperature observation using temperature loggers was conducted from March to June 2009, covering the spawning period of most cyprinid fishes, the dominant taxonomic group of fish in the lake. During the daytime, the hourly average temperature was different between the surface and the bottom layer both in the littoral and pelagic zones; those differences disappeared during the nighttime, indicating nocturnal vertical water mixing. Daily average temperature, as well as intraday temperature variation, was negatively correlated with the site depth both in the surface and the bottom layers, suggesting that the littoral zone is warmer than the pelagic zone but less stable as a thermal habitat for aquatic species. Based on its geological location and depth, Lake Erhai could be classified as a polymictic lake, which tends to be well mixed; however, our study results indicate a high heterogeneity in water temperature. This specific thermal environment supports local fauna and flora and thus must be conserved to ensure their survival.