As of July 2017, the International Union for Conservation of Nature (IUCN) lists 1,000 critically endangered fish species, including 87 which are tagged as possibly extinct. 3.0% of all evaluated fish species are listed as critically endangered. The IUCN also lists four fish subspecies as critically endangered. Of the subpopulations of fish evaluated by the IUCN, 20 species subpopulations and one subspecies subpopulation have been assessed as critically endangered.