The effect of exercise on the growth and hematology of diploid and triploid brook trout (Salvelinus fontinalis)

The blood of triploid brook trout, Salvelinus fontinalis, contains relatively high numbers of immature erythrocytes that are suggestive of the premature release of mitotically dividing cells into the peripheral circulation, a condition known to occur in fish subjected to stress. The objective of this research was to determine whether moderate exercise, known to reduce stress in fish, reduces the incidence of such cells, and improves growth in triploid brook trout. Triploids and control diploids were maintained in tanks with water currents adjusted to either 5 cm/s (non-exercise) or 10 cm/s (moderate exercise). Weight and length measurements were taken between October 1999 and March 2000, and blood samples collected for the preparation of blood smears. There were no effects of exercise or ploidy on growth. Blood cell counts confirmed, however, that moderate exercise does decrease the incidence of dividing erythrocytes in triploid brook trout.