Abstract Rehulka 1.: The Blood Indices of the Rainbow Trout, Oncorhynchus mykiss (Walbaum; in

Indices of the peripheral blood of the rainbow trout, Oncorhynchus mykiss (Walbaum) were studied in cases of affected skin. occurring on mass. Haematological and biochemical analyses were carried out in 8 to 10 fish from one group of fish subjectively judged as healthy and another as diseased.A significant reduction (P = 0.0 I J. as compared to the values obtained from clinically healthy fish, was recorded in the red blood cells count (RBC: 0.55 vs 0.95 TIL), haematocrit (PCV: 0.200 vs 0.344) and haemoglobin (Hb: 36.8 vs 65.9 gIL). As to the biochemical parameters of the blood plasma, a statistically signiticant (P = 0.01) decrease occurred in total protein (TP: 10.7 vs 35.6 gIL), cholesterol (CHOL: 0.74 vs 5.75 mmollL), triglycerides (TG: 0.37 vs 2.37 mmollL) and calcium (Ca2+: 2.09 vs 3.25 mmollL). Increases in the urea (BUN: 1.7 vs 0.5 mmollL) and glutamyl transferase activities (GMT: 0.48 vs 0.09 J,lkat/L) were observed in the affected fish at the same level of statistical significance. At a significance level of P = 0.05 we recorded a decrease in lactate dehydrogenase activity (LDH: 40.98 vs 15.85 ~kat/L). Electrophoresis on agarose gel showed mainly a reduction of albumins. Haematology, blood chemistry. aerolllonad epidemic, Oncorhynchus mykiss Intensive rainbow trout farming requires veterinary supervision to be provided b