Dorsal aorta catheterization in rainbow trout (Salmo gairdneri). II. Glucocorticoid levels, hematological data and resumption of feeding for five days after surgery.

Plasma glucocorticoid levels, leucocrit, hematocrit and resumption of feeding were recorded in catheterized rainbow trout for 5 days after cannulation of the dorsal aorta. In some animals, glucocorticoids returned to basal levels, while a regular and active feeding behaviour was resumed shortly after cannulation. In contrast, other individuals demonstrated relatively high and irregular glucocorticoid concentrations and constantly refused food. The leucocrit was significantly depressed from 30 min until 24 h after cannulation; after day 1, this parameter exhibited a recovery profile in all animals, independently of the glucocorticoid levels. During the 5-day experimental period, seven blood samples were taken, amounting to 10 p. 100 of the total blood volume. In some individuals, the hematocrit continuously declined, suggesting low compensation for the erythrocyte loss. The results of this investigation indicate that well-adapted catheterized trout may be obtained a few days after the operation. Feeding activity should be checked carefully and particular caution used when determining the volume and frequency of the blood samples.