Acute toxicity tests of Lannate insecticide on three commercially important fingerlings of the Visayas region, Central Philippines
Abstract
The study examines the acute toxicity (48 h) of Lannate insecticide to three species of fish fingerling with different osmoregulatory capabilities, i.e., Oreochromis sp. (GET-Excel tilapia), Lates calcarifer (seabass), and Siganus fuscescens (rabbitfish). After 2 weeks acclimatization period in the laboratory, static bioassays were conducted to determine the median lethal concentration (LC50). Three acute toxicity trials were conducted to determine mortality and observations were done at 3, 6, 12, 24, and 48 h. After 48 h, the mean LC50 values were 7.73 ppm for GET-Excel Tilapia, 6.11 ppm for Lates calcarifer, and 1.47 ppm for Siganus fuscescens. Immediate changes in breathing rate were also observed upon introduction of Lannate into the medium, with Siganus fuscescens having the highest average breathing rate (74/min). Mortality increased with Lannate concentrations with Siganus fuscescens determined to be most sensitive to Lannate among the three species. Recent use of Lannate insecticide in killing nearshore fishes and the result of this study should serve as a wake-up call to regulate usage of this insecticide at the barangay level, i.e., the smallest administrative unit in the Philippines.
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