Possible explanations could include increased metabolic demand with warmer temperature,
leading to higher Hct; increased Hct to maximize overall O2 uptake at warmer acclimations in response to decreased O2 solubility in warmer water; decreased hematopoiesis caused by colder acclimation temperatures; or increased blood viscosity at colder temperatures,which may be countered by decreased Hct, reducing the work requirement for the heart