Whole body and tissue blood volumes of two strains of rainbow trout (Oncorhynchus mykiss)

1. Estimates of apparent packed cell, plasma and total blood volumes for the whole body and for 13 selected tissues were compared between Kamloops and Wytheville strains of rainbow trout (Oncorhynchus mykiss) by the simultaneous injection of two vascular tracers, radiolabeled trout erythrocytes (⁵¹Cr-RBC) and radioiodated bovine serum albumin (¹²⁵I-BSA).

2. Whole body total blood volume, plasma volume and packed cell volume were slightly, but not significantly greater in the Wytheville trout, whereas, the apparent plasma volumes and total blood volumes in 4 of 13 tissues were significantly greater in the Kamloops strain.

3. Differences were most pronounced in highly perfused organs, such as the liver and kidney and in organs of digestion such as the stomach and intestines.

4. Differences in blood volumes between the two strains may be related to the greater permeability of the vascular membranes in the Kamloops strain fish.