Definition of blackfishes:
(n) :
A pilot whale (Globicephalus spp.) and occasionally also used for various other whales).
(n) :
(Canada, US) Either of two dark-coloured fish of the west Atlantic, the tautog of New England (Tautoga onitis) and the black sea bass (Centropristis striata).
(n) :
(Australia, New Zealand) Any of various dark-coloured fishes of Australasia, especially the luderick (Girella tricuspidata), and a freshwater fish, Gadopsis marmoratus.
(n) :
Any of various dark-coloured fish of the Old World, especially the rudderfish (Centrolophus niger).
(n) :
(chiefly Scotland) An Atlantic salmon, Salmo salar, especially a female after spawning.
(v) :
(fishing) To go fishing for blackfish.