Toxic and sublethal effect of formalin on freshwater fishes

Supranee Chinabut Chalor Limsuwan Kamonporn Tonguthai Temdoung Pungkachonboon;Fisheries and Aquaculture Management Division

Toxic and sublethal effect of formalin on freshwater fishes

Autores

Supranee Chinabut Chalor Limsuwan Kamonporn Tonguthai Temdoung Pungkachonboon;Fisheries and Aquaculture Management Division

Descripción

Toxicity of formalin to three freshwater fish species was determined by using static bioassay. The 96-hour LC50 of formalin on silver barb (Puntius gonionotus Bleeker), common carp (Cyprinus carpio Linn.) and snakehead fish (Channa striatus Flower) were 67–80, 106–128 and 147–166 ppm, respectively. Toxicity of formalin was most obvious during the first 24 hours of exposure. Water pH and hardness had no effect on the toxicity. There were significant differences in percentage weight gain among the control common carp fry and fish treated with 25, 50 and 75 ppm formalin for 8 weeks. Fish exposed to 75 ppm formalin had the lowest growth throughout the 8-week period. However, no histological changes were observed in gills, liver, kidney, spleen digestive tract and muscle of common carp fry exposed to formalin during the 8-week period. No histological changes were found in common carp and snakehead fry that survived from acute toxicity test but hyperplasia of gill lamellae and fatty degenera tion in the liver were observed in silver barb.