Some pathological changes in Nile Tilapia and Nile Perch from Lake Victoria.

Abstract

Gross and microscopic lesions especially those associated with pollutants were investigated in Nile tilapia (Oreochromis niloticus) and Nile perch (Lates niloticus) from Lake Victoria. A total of 104 live fish were bought from fishermen from Homa Bay and Suba districts. During post mortem examination, lesions observed were recorded; and kidney, gills, liver, spleen, heart, stomach, intestine and gonadal tissues taken and preserved in 10% buffered formalin for histological processing. Gross lesions observed were hyperemia, hemorrhages in various tissues; skin ulcers, eye opacity; cooked liver appearance, fibrosis, gray spots and bile imbibitions; atrophied and cystic gonads; and fish skeletal deformity. Histological lesions were gill aneurysms, kidney tubular lumen occlusions, increased melanomacrophage aggregation in the liver, kidney and spleen; liver sinusoidal hemorrhages, fatty degeneration, hepatocytes‟ vacuolations, necrosis, bile stasis and granulomas; kidney granulomas; testicular and ovarian degeneration and cysts; myocarditis and myositis. The liver had majority lesions that were severe in both fish species. These lesions can be caused by variable aetiologies, including pollutants. In all, 63% of the Oreochromis niloticus and 58% Lates niloticus had histological lesions. Further studies are required to establish the cause of the lesions.