Effects of acclimation to elevated water temperature and hypoxia on thermal tolerance of the threatened Pugnose Shiner Notropis anogenus

For freshwater fishes, elevated water temperatures associated with climate warming and hypoxia can co-occur and are likely to interact as both affect oxidative metabolism. We quantified the effects of acclimation to elevated temperature and hypoxia on the thermal tolerance of Pugnose Shiner (Notropis anogenus), a cyprinid fish threatened in its Canadian range. In one experiment, Pugnose Shiner underwent 2-week sequential acclimations to six increasing temperatures. Fish acclimated to warmer waters increased their critical thermal maximum (CTmax), while the agitation temperature (Tag) was 3.4C lower than CTmax. In another experiment, fish were acclimated to three dissolved oxygen treatments (>95%, ~56% or ~40% air saturation) for 2 weeks, and tested under >95% and 40% conditions. CTmax was lower when measured under 40% for normoxia-acclimated fish, but not for hypoxia-acclimated fish. Hypoxia-acclimated fish had higher Tag and smaller agitation windows than normoxia-acclimated fish, suggesting that hypoxia acclimation improves aspects of thermal tolerance. We examine the plasticity of thermal tolerance of Pugnose Shiner, showing that they may be more vulnerable to high temperatures compared to other non-imperilled Notropis species.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author