Relationships between temperature and blood oxygen in the largemouth bass

Measures of physiological response of northern largemouth bass to various temperatures were taken to ascertain the degree of adaptation of the bass to its environment. These measures include hemoglobin, red-cell count, arterial blood oxygen, oxygen capacity, and lactic acid. The amount of arterial blood oxygen is more closely related to water temperatures than to oxygen content of the water. At high body temperatures during quiescence, hemoglobin increases in the gills, the opercular pulse rate increases, and the lactic acid level rises considerably. In blood taken from bass at various temperatures, increased lactic acid improves the combining power of hemoglobin with oxygen. Percentage loss of oxyhemoglobin is more directly related to lactic acid level than to the possible destructive effect of high temperatures on the hemoglobin in vivo. The northern largemouth bass appears to occupy certain habitats through physiological lability rather than through direct adaptation.