C.S. Tucker; R. Francis-Floyd; M.H. Beleau
Delta Branch Experiment Station, Mississippi State University, Stoneville, MS
Pathological changes associated with chronic exposure of channel catfish
to sublethal concentrations of environmental nitrite is described. Other than mild
methemoglobinemia (<15% of total hemoglobin), no lesions were evident in fish exposed to
NO2:C1 molar ratios of <0.12. Fish exposed to NO 2:C1 molar ratios of 0.25 or greater
developed a moderate hemolytic anemia after one to two weeks of exposure. Mild hemosiderosis in
hematopietic tissues and increase in immature circulating erthrocytes were evident. Other
lesions included mild intralamellar hyperplasia and hypertrophy and mild multifocal necrosis of
the liver and anterior kidney. The relevance of these findings to management of nitrite
toxicosis in cultured catfish is discussed.