Effects of formalin treatment on the blood composition of salmon (Salmo salar) and rainbow trout (Salmo gairdneri).

The effects of treatment with 250 ppm or 1250 ppm formalin on the blood composition were studied in 48 salmon and 56 trout in northern Finland. The blood haemoglobin and packed cell volume of the salmon controls were slightly lower but blood glucose and plasma total protein values significantly (P less than 0.001) lower than those of the rainbow trout. Formalin treatment influenced all blood values studied. Blood Hb and PCV values of the salmon and rainbow trout increased slightly after formalin exposures. The highest Hb values were measured in the fishes exposed twice to 250 ppm formalin or four times to 1250 ppm formalin for 30 min at 24 hr intervals. The blood glucose concentration of the salmon increased when exposed twice to 250 ppm or 1250 ppm formalin for 30 min at 24 hr intervals. The blood glucose value of the rainbow trout was lowest (4.4 mmol/l) when exposed to 250 ppm formalin. High blood glucose values were measured for the groups exposed twice to 250 or 1250 ppm formalin for 30 min at 24 hr intervals. Blood lactate values decreased during exposures. The plasma protein concentration of the salmon and rainbow trout increased during formalin treatments.