Preferred, Avoided, and Lethal Temperatures of Fish During Rising Temperature Conditions

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Abstract
Selected temperatures increased for 15 fish species in a laboratory gradient when acclimated to 3.degree. C increments from 12-27.degree. C. Temperature preferences exceeded acclimation temperatures between 12-27.degree. C for all except the telescope shiner (Notropis telescopus), yellow perch (Perca flavescens), rainbow trout (Salmo gairdneri), brown trout (S. trutta) and brook trout (Salvelinus fontinalis). At 30, 33 or 36.degree. C acclimation, preferred temperatures were less than the acclimation temperature. The highest temperature preferences occurred at acclimations of 27, 30 or 33.degree. C. Bluegill (Lepomis macrochirus), spotted bass (Micropterus punctulatus), rockbass (Ambloplites rupestris) and the spotfin shiner (Notropis spilopterus) consistently selected the highest temperatures, while the lowest temperatures were preferred by the salmonids. Final temperature preferences were usually greater than 29.degree. C for most centrarchids, above 24.degree. C for most cyprinids and less than 19.degree. C for salmonids. Avoidance temperatures increased as acclimation temperature increased. Upper avoidances tested at high acclimation temperatures (30-36.degree. C) either equalled or exceeded the 7-day upper lethal temperature limit of the species by 1-2.degree. C, while avoidances were below this upper lethal limit when tested at the acclimation temperature closest to the species'' final temperature preference. Other species studied were Campostoma anomalum, Pimephales promelas, P. notatus, Notropis rubellus, Micropterus dolomieui and Hypentilium nigricans.