Relationships between Temperature and Blood Oxygen in the Largemouth Bass

Studies of adaptations of various organisms to different factors of the environment are numerous; among these, environmental temperature in relation to poikilothermous animals has received considerable attention. It is generally agreed that for each organism and life stage, when all other factors remain constant, there will be an optimum range of temperature. The physiological responses of an organism to temperatures above and below this optimum range are stress responses and reflect the degree of lability or of adaptation in the physiological processes. Lack (1945) stated that closely related species can rarely occupy the same habitat. In the process of competition between two similar species for comparable living conditions, one group will either become extinct or eventually occupy the peripheral areas of the same general habitat. The largemouth bass (Micropterus salmoides) and the smallmouth bass (M. dolomieu) appear to present such a pattern. The deeper, clearer, and colder areas of northern lakes and streams are dominated by the smallmouth bass, while the largemouth bass is found in the more shallow, weedy, and warmer bays. The successful existence of the largemouth bass in warmer, more stagnant areas can have resulted either from a true adaptation to these conditions or from a physiological lability that at times may have been taxed severely. The purpose of this study was to ascertain certain relationships between water temperature and physiological response in the northern largemouth bass taken from a typical, shallow, thickly vegetated, northern lake.