Cottinella boulengeri in the context of "Cottidae"

The Cottidae are a family of fish in the superfamily Cottoidea, the sculpins. Following major taxonomic revisions, it contains about 118 species in 18 genera, the vast majority of which are either restricted to freshwater habitats or are amphidromous. They are referred to simply as cottids to avoid confusion with sculpins of other families.

Cottids are distributed throughout the Northern Hemisphere, especially in boreal and colder temperate climates. They are especially diverse in Lake Baikal and surrounding river basins. Only a few cottids inhabit marine habitats. Other sculpins restricted to marine habitats are now placed in the family Psychrolutidae. In Lake Baikal, many cottids live in deep water, below 170 m (560 ft). There are 24 known species in seven genera. These include, for instance, Abyssocottus korotneffi and Cottinella boulengeri which are among the deepest-living freshwater fish. Baikal is the deepest lake on Earth (1,642 m or 5,387 ft) and sculpins occupy even its greatest depths.