Elevated temperatures increase chlorpyrifos toxicity in nile tilapia (Oreochromis niloticus) larvae

Global warming and the extensive use of chlorpyrifos pose serious threats to the hatching success, growth, and survival of Nile tilapia larvae (Oreochromis niloticus). This study aimed to evaluate the combined effect of chlorpyrifos toxicity and elevated temperatures on tilapia larvae. A completely randomized design (CRD) was used with three temperature levels (28°C, 31°C, and 34°C) and two chlorpyrifos concentrations (0 µg/L and 32 µg/L), totaling six treatments with three replicates each. Parameters observed included hatching rate, daily growth rate (DGR), specific growth rate (SGR), absolute growth rate (AGR), and malformation rate. Measurements were conducted daily from the first day of hatching until the end of the larval phase (Day 8). Results showed the highest hatching rate (85.33%) was achieved at 34°C without chlorpyrifos, while the lowest rate (20%) occurred at 28°C with chlorpyrifos exposure on Day 2. DGR and SGR significantly decreased at 34°C with chlorpyrifos exposure, reaching 0.0003 g/day and 3.73%/day, respectively, compared to 28°C without chlorpyrifos (0.0011 g/day and 10.78%/day). AGR remained stable across all temperatures, showing no significant differences with or without chlorpyrifos. The malformation rate, including abnormalities such as lordosis and kyphosis, increased with higher temperatures and chlorpyrifos exposure, with the highest rate (25%) recorded at 34°C with 32 µg/L chlorpyrifosKeywords:ChlorpyrifosNile TilapiaHatching RateLarval Growth