CRITICAL THERMAL MINIMA AND MAXIMA OF 3 FRESH-WATER GAME-FISH SPECIESACCLIMATED TO CONSTANT TEMPERATURES

A total of 120 critical thermal maxima (CT maxima) and 120 critical th ermal minima (CT minima) were determined for channel catfish, largemou th bass and rainbow trout acclimated to three constant temperatures: 2 0, 25 and 30 degrees C in catfish and bass, and 10, 15 and 20 degrees C in trout. Highest mean CT maximum and lowest mean CT minimum measure d over these acclimation temperatures were 40.3 and 2.7 degrees C (cat fish), 38.5 and 3.2 degrees C (bass) and 29.8 and similar to 0.0 degre es C (trout). Temperature tolerance data were precise with standard de viations generally less than 0.5 degrees C. Channel catfish had the la rgest thermal tolerance scope of the three species while rainbow trout had the lowest tolerance of high temperatures and the highest toleran ce of low temperatures. In all species CT minima and CT maxima were hi ghly significantly linearly related to acclimation temperature. Within each species, slopes relating CT maxima to acclimation temperature we re approximately half as large as those relating CT minima to acclimat ion temperature, suggesting that acclimation temperature has a greater influence on tolerance to low rather than high temperatures. Slopes r elating both CT minima and CT maxima to acclimation temperature fdr th e two warm-water species were similar and approximately twice those fo r the rainbow trout.