Understanding the ability of fishes to tolerate low dissolved oxygen (DO) is important not only to our understanding of the ecology of aquatic systems, but also for flow management in regulated lotic systems. Historical flow management guidelines have been based on critical oxygen concen- trations and incipient lethal levels from just a few species, and data on nongame fish species are lacking. Here we quantify respiration rate, critical DO concentration at routine metabolic rate, and regulatory capacity across temperatures for five nongame fish species. Oxygen consumption patterns rep- resented a continuum between regulation and conformation, as ability to regulate was affected differently by temperature among species, declining with increasing temperature in blackbanded darter (Percina nigrofasciata) and increasing with temperature for banded sculpin (Cottus carolinae). Further, oxygen consumption was not affected by temperature in bronze darter (Percina palmaris), greenbreast darter (Etheostoma jordani), and blacktail shiner (Cyprinella venusta). Critical oxygen levels increased with temperature for blacktail shiner, greenbreast darter, and blackbanded darter, but did not change with temperature for bronze darter or banded sculpin. Given this among-species variation, protections based on data from a limited number of taxa may not effectively protect habitat for entire fish communities.
