A dorsal cannulation technique is described. It has been employed for
repeated blood sampling in unanaesthetized rainbow trout (Salmo gairdneri)
kept singly in special receptacles described in the paper. The level of the
studied haematological parameters (Haematocrit, Hb, glucose, lactate, K+, Na+
, Ca2+) differed between fish kept in receptacles for 1 week and free- swimming fish, most probably owing to differences in the motility of the
fish. The receptacle seems to minimize visual and handling disturbances, and
permits both the standardization of experimental conditions and quick and
easy sampling via the dorsal aorta cannula. The general variation in the
blood parameter values was very small compared with the previously reported
variation in such values for rainbow trout.