In September 2016, the International Union for Conservation of Nature (IUCN) listed 643 endangered fish species.
For a species to be considered endangered by the IUCN it must meet certain quantitative criteria which are designed to classify taxa facing "a very high risk of extinction".
Additionally 3191 fish species (21% of those evaluated) are listed as data deficient, meaning there is insufficient information for a full assessment of conservation status.
As these species typically have small distributions and/or populations, they are intrinsically likely to be threatened, according to the IUCN.
[3] This is a complete list of endangered fish species and subspecies evaluated by the IUCN.