Temperatures Selected and Avoided by Fish at Various Acclimation Temperatures

Abstract

Temperatures selected and avoided by 13 fish species, evaluated at decreasing increments of 3 C from 30 to 6 C, declined as the acclimation temperature decreased from summer to winter. As acclimation levels declined the difference between acclimation and selected temperatures increased for centrarchids and cyprinids, whereas the difference between these two temperatures increased for trout above and below the 18 C level of acclimation. Bluegill (Lepomis macrochirus) and spotted bass (Micropterus punctulatus) selected the highest temperatures at all acclimation levels, followed by channel catfish (Ictalurus punctatus), green sunfish (Lepomis cyanellus), smallmouth bass (Micropterus dolomieui), spotfin shiner (Notropis spilopterus), and other cyprinids. Rainbow (Salmo gairdneri) and brook (Salvelinus fontinalis) trout selected the lowest temperatures. A linear regression of the selection vs. the acclimation temperatures was plotted for cyprinids, centrarchids, and salmonids.As the acclimation temperature was lowered, temperatures avoided decreased and the difference between the upper and lower avoidance range increased at each acclimation level. Eurythermal species, centrarchids, ictalurids, and most cyprinids, generally had a range difference of at least 10 C or more between the upper and lower avoidance temperature at each acclimation level.