Multiple Thermal Metrics of Four Notropis Species in Missouri (2022-2024)

We estimated thermal preference, acclimated chronic exposure, metabolic thermal optima, and critical thermal maximum for four species in the Notropis genus during 2022-2024. Thermal preference was estimated for Blacknose Shiner (Notropis heterolepis) and Ozark Shiner (N. ozarcanus) for individuals acclimated at both 22°C and 26°C for a minimum of two weeks using a behavioral shuttlebox. Acclimated chronic exposure was estimated for Topeka Shiner (N. topeka), Blacknose Shiner, Ozark Shiner, and Carmine Shiner (N. percobromus) using six temperature treatments at 2°C intervals across a range of 10°C. Fish were fed to satiation daily and growth was determined over a period of 60 days. Metabolic thermal optima was estimated for Topeka Shiner, Blacknose Shiner, Ozark Shiner and Carmine Shiner using an electron transport system assay that generates an enzyme activity curve following 3°C intervals from 9 to 57°C for each individual. Individuals from Missouri populations were tested for each species, and individuals from Wisconsin populations for Blacknose Shiner and Carmine Shiner were also tested to assess population-level differences across the species range. Critical thermal maximum corresponds to the upper thermal limit that an organism can withstand and is defined as the upper temperature where loss of equilibrium occurs for fish. Topeka Shiner, Blacknose Shiner, Ozark Shiner, and Carmine Shiner were acclimated at either 22°C or 26°C for a minimum of two weeks prior to being tested. Individuals were placed in a test aquarium equipped with a heater and thermometer and the temperature was increased at a rate of 0.3°C per minute starting at the acclimation temperature until the individual lost equilibrium.