Ecotoxicology of drugs used in fish disease treatment

The fish Hyphessobrycon eques and Piaractus mesopotamicus, the snail Pomacea canaliculata, the aquatic plant Lemna minor and the microcustacean Daphnia magna were selected to evaluate the lethal or effective concentration (LC50/EC50) and the environmental risk of florfenicol (FLO), enrofloxacine (ENR), thiamethoxan (TH) and toltrazuril (TOL). For this, the organisms were acclimated in a bioassay room under controlled temperature and photoperiod, and then exposed to increasing drugs concentrations according to specific standard for each organism. L. minor is the sole organism which showed toxicity to FLO LC50; 48 h of 97.03 mg/L, which causes medium environmental risk. P. canaliculata was more sensible to ENR (14.64 mg/L), which causes high risk to the bioindicators. P. mesopotamicus was more sensible to TH toxicity (16.97 mg/L), which causes high risk also; followed by H. eques. TOL causes medium risk and it is more toxic for P. mesopotamicus (3.72 mg/L), followed by H. eques. L. minor can be used as a bioindicator for florfenicol toxicity, P. canaliculata for enrofloxacine and H. eques for TH and TOL, emphasizing that enrofloxacine and thiamethoxan cause high environmental risk.   Key words: Environmental monitoring, disease, environmental impact, chemotherapeutic products, aquaculture drugs.