Variations in Hematocrit Values of Fish Blood during Incubation

We measured the Ht of rainbow trout blood incubated at 0.3, 10 and 20°C under different conditions. For “astatic” determinations, blood in the same test tube was agitated prior to each assay performed at 5 intervals; in “static” determinations, the original blood sample was dispersed into 5 tubes and the content of each tube was agitated once and assayed at appropriate intervals after sampling. At all tested temperatures, the Ht values obtained under “static” conditions were higher than under “astatic” conditions, possibly because of a difference in the O2 tension of the assayed samples. Under static incubation conditions (0.3°C, 2h), the sample volume in the range from 0.4-1.0ml did not affect the Ht value. Samples incubated at 0.3°C in capillary tubes under static conditions manifested higher Ht values than samples incubated in test tubes under astatic conditions. The effect of temperature (0.3, 10, 20°C) on Ht under static conditions was also studied in masu salmon, Oncorhynchus masou and common carp. Masu salmon blood manifested a pattern similar to rainbow trout blood; no remarkable changes in the Ht value of carp blood were recognized under these conditions.