Acute Toxicity and Risk Assessment of Florfenicol for Nile Tilapia Larvae

The aim of this study was to determine the median lethal concentration (LC_50-96h), effective concentration (EC_50-96h), risk assessment, and development of Nile tilapia Oreochromis niloticus larvae submitted to florfenicol (FF) exposure. Fish (n = 147; 8.6 ± 0.6 mg; 7 fish/aquarium) were randomly distributed in 21 aquaria (1 L) and exposed to five concentrations of FF 58.73; 131.31; 198.96; 241.88 and 381.81 mg L^-1 plus one control and a control with solvent, totalizing seven treatments and three replicates. The estimated median LC_50-96h of FF for Nile tilapia larvae was 349.94 mg L^-1. The EC_50-96h of FF was 500 mg L^-1 for weight reduction and was 1040 mg L^-1 for length reduction. After the exposure period, final weight and length differed (p < 0.05) among treatments, showing the lowest biometric values ​​with the highest concentrations of FF. The pH and dissolved oxygen were altered (p < 0.05) during the experimental period. The FF high doses used to determine the LC 50 after 96 h negatively affected the development of the larvae. On the other hand, through risk assessment analysis this antibiotic can be classified as low toxicity to Nile tilapia larvae and show low environmental risk.