Selected temperatures increased for 15 fish species in a laboratory gradient when acclimated to 3 °C increments from 12 to 27 °C. Temperature preferences exceeded acclimation temperatures between 12 to 27 °C for all except the telescope shiner (Notropis telescopus), yellow perch (Perca flavescens), rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis). At 30, 33, or 36 °C acclimation, preferred temperatures were less than the acclimation temperature. The highest temperature preferences occurred at acclimations of 27, 30, or 33 °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 °C for most centrarchids, above 24 °C for most cyprinids, and less than 19 °C for salmonids.Avoidance temperatures increased as acclimation temperature increased. Upper avoidances tested at high acclimation temperatures (30–36 °C) either equalled or exceeded the 7-day upper lethal temperature limit of the species by 1–2 °C, while avoidances were below this upper lethal limit when tested at the acclimation temperature closest to the species' final temperature preference.

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1991. Tissue-specific patterns of synthesis of heat-shock proteins and thermal tolerance of the fathead minnow (Pimephales promelas). Can. J. Zool. 69: 2021-2027. Qualitative and quantitative differences in the heat-shock response in brain, gill, and striated muscle tissues of the fathead minnow (Pimephales promelas) were investigated. The maximum sublethal heat-shock temperature was 34°C. The heat-shock proteins (hsps) induced, their biosynthetic rates, minimum temperatures required for induction, and maximum temperatures at which each tissue synthesized hsps were tissue specific. Six hsps were induced in gill tissue (100,90,78,70,68, and 60 kDa), four in muscle tissue (100,90,78, and 70 m a ) , and three in brain tissue (90,70, and 68 m a ) . Minimum temperatures required for inducing the stress response in gill, muscle, and brain were 28, 31, and 32"C, respectively. Maximum hsp synthesis and accumulation occurred at 33°C for the brain and 34°C for muscle and gill. Synthesis and accumulation of hsps decreased to near pre-exposure levels in the brain at 34°C. The fact that brain tissue synthesized the fewest hsps and had the lowest capacity for synthesis at the upper thermal limits of the organism supports the hypothesis that the central nervous system governs the thermal limits to survival in poikilotherms. DYER, S. D., DICKSON, K. Lr, ZIMMERMAN, E. G., et SANDERS, B. M. 1991. Tissue-specific patterns of synthesis of heat-shock proteins and thermal tolerance of the fathead minnow (Pimephales promelas). Can. J. Zool. 69 : 2021-2027. Les diffdrences qualitatives et quantitatives de la rkaction protkinique aux chocs t e~i q u e s ont Ct C mesurCes dans le cerveau, les branchies et les muscles striCs chez le T2te-de-boule (Pimephales promelas). La tempkrature de choc sublCtale supkrieure a Ct C CvaluCe A 34°C. Les protCines de choc spicifiques (hsp) synthCtisCes, leur taux de biosynthkse, les tempCratures minimales nCcessaires A la synthkse, et les tempkratures maximales auxquelles chaque tissu synthCtisait les hsp Ctaient spCcifiques A chaque tissu. Six de ces protCines ont Ct C synthCtisCes dans les branchies (100,90, 78,70,68 et 60 m a ) , quatre dans les muscles (100, 90,78 et 70 kDa) et trois dans le cerveau (90,70 et 68 m a ) . Les tempkratures minimales requises pour provoquer un stress ont Ct C estimCes A 28°C dans le cas des branchies, 3 1°C dans le cas des muscles et 32°C dans le cas du cerveau. C'est A 33°C dans le cerveau et A 34°C dans les muscles et les branchies que se sont produites la synthkse la plus active et l'accumulation maximale des protCines. A 34"C, la synthkse et l'accumulation des protCines sont retombCes A des valeurs voisines des valeurs enregistrdes avant le choc dans le cerveau. Le fait que le tissue du cerveau synthCtise le moins grand nombre de protkines de choc therrnique et qu'il ait la plus faible capacitC de synthdtisation aux limites lCtales supCrieures de l'organisme semble indiquer que c'est le systkme nerveux central qui fixe les seuils thermiques de survie chez les,poikilot...

Robust canonical correlation and classification methods were used to evaluate relationships between ambient toxicity and instream biological response. Ten studies of freshwater aquatic systems were used in the analysis. These studies included eight site studies conducted by the U.S. Environmental Protection Agency's Complex Effluent Toxicity Testing Program, one study by the University of Kentucky and one study by the University of North Texas. Results from ambient toxicity tests, including Ceriodaphnia neonate production and Pimephales promelas dry weight and survival, were used to predict impact at sampling stations. Instream biological response variables, including fish and benthic richness, were used to classify whether or not a station was impacted. The strength of the relationship between ambient toxicity and instream impact was determined by statistically evaluating agreement between the predicted and observed impacts. Results of the analysis showed that statistically significant relationships between ambient toxicity and instream impact were found in each of the studies.