Database of critical oxygen level (Pcrit) in freshwater and marine fishes 1974 - 2015 dataset https://portal.medin.org.uk/portal/start.php?tpc=009_CEFASc9a84dbd-48f5-400f-a743-00b8f452a2c8 This is a comprehensive database of critical oxygen (Pcrit) values from freshwater, marine and euryhaline teleost fish compiled from published literature. The database incorporates 331 measurements of Pcrit from a total of 96 published studies and covers 151 fish species from 58 families. It provided the opportunity to critically examine methodologies for determining Pcrit as well as its usefulness as an indicator of hypoxia tolerance in fish. Additional data are included (when available) on various abiotic and biotic interactions with hypoxia and their effect on Pcrit. These included: water temperature, salinity, pH, carbon dioxide, sex, photoperiod, diet, ration size, body size (mass and length), respirometry method. The aim was to provide a widely accessible central repository of physiological trait data that will facilitate future studies of fish ecology, conservation and management. 20210331 20210312