Toxicity of four commonly used chemotherapeutic compounds to fry of the African catfish, Clarias gariepinus (Burchell)

Acute toxicity tests were carried out for four compounds commonly used against various fish pathogens to determine their 24-h LC₅₀ values to fry of the African catfish, Clarias gariepinus (Burchell). Compounds tested and their calculated 24-h LC₅₀ values (mg l^?1) were as follows: praziquantel (13.4); malachite green oxalate (0.14); acriflavin neutral (10.0); and mebendazole (315). The results show that dosage levels of malachite green oxalate, praziquantel and acriflavin neutral recommended in the literature for the control of most fish ectoparasitoses caused substantial mortalities and cannot be applied to Clarias gariepinus fry.