Tolerance level and histopathological response of milkfish (Chanos chanos) fingerlings to formalin

Abstract

Static 96-h bioassays were conducted on milkfish (Chanos chanos ) fingerlings with formalin at concentrations ranging from 50 to 500 ppm. The 24-, 48-, 72-, and 96-h median lethal concentration values (LC50) were 322, 260, 241, and 232 ppm formalin, respectively. Histological analyses of gills, liver, and kidney tissues revealed significant pathological changes even with the sublethal concentrations. The intensity of cell damage increased with increasing concentration and exposure to the chemical. Formalin treatments caused hyperplasia, epithelial separation, and necrosis in the gills; cloudy swelling, hemorrhage, deposition of pigments, and necrosis in liver parenchyma; and degeneration of renal tubules. Partial recovery of tissue was observed in fish after 10 days in formalin-free seawater.