Toxicity of Malathion to Nile Tilapia <I>Oreochromis Niloticus</I> (Linn.) Fingerlings

  • Virginia Cariño
  • Emmanuel Capinpin


The toxicity of a commercial grade malathion on Nile tilapia, Oreochromis niloticus, fingerlings was determined. The 24, 48, 72, and 96-h LC50 of malathion on Nile tilapia fingerlings were 7.19, 5.43, 5.34, and 5.30 mg/l, respectively. Behavioral changes in fish included rapid opercular movement, hyperexcitability, darkening of the body, and contraction of trunk muscles. Moribund fish displayed labored opercular movement, severe contraction of the trunk muscles, erratic swimming, and total loss of equilibrium. A safe level of less than 0.53 mg/l malathion for Nile tilapia fingerlings was considered.