What is the meaning of Blackfish?

An Atlantic salmon, Salmo salar, especially a female after spawning.

Any of various dark-coloured fish of the Old World, especially the rudderfish (Centrolophus niger).

A pilot whale (Globicephalus spp.) and occasionally also used for various other whales).

Either of two dark-coloured fish of the west Atlantic, the tautog of New England (Tautoga onitis) and the black sea bass (Centropristis striata).

Any of various dark-coloured fishes of Australasia, especially the luderick (Girella tricuspidata), and a freshwater fish, Gadopsis marmoratus.

To go fishing for blackfish.

To adopt signifiers of black identity (for example, by darkening the skin, or wearing traditionally black hairstyles).

Source: wiktionary.org