Determination of thermal tolerance parameters of swordtail (Xiphophorus helleri) and platy (X. maculatus)

Thermal tolerance parameters of Swordtail (Xiphophorus helleri) and Platy (X. maculatus) at three acclimation temperatures were determined in the study. The CTMin values at 20, 24 28°C acclimation temperature were 8.82, 10.22, 11.03°C respectively for Platy and 9.38,11.5, 13.23°C for Sworstail, while CTMax values were 37.41,39.19, 40.52°C for Platy and 36.94, 38.89, 40.07°C for Sworstail. Accordingly, acclimation temperature affected the lower and upper temperature tolerances of fish by 3-4°C. The CTMin ARR values varied between 0.42-0.42 in Sworstail and 0.20-0.34 in Platy, While CTMax ARR ranged between 0.29-0.48 in Sworstail and 0.33-0.44 in Platy depending on acclimation temperature. Thermal tolerance polygon area of Platy (232°C2) was slightly higher than that of Swortail (217.3°C2). The fact that both fish species have lower temperature tolerances is limits their geographic distribution and aquaculture in subtropical climates where the water temperature drops to 10°C in winter.