coalfish vs sablefish

coalfish

noun
  • any of several blackish fish, especially Pollachius virens, a pollack, and Anoplopoma fimbria, sablefish. 

sablefish

noun
  • A dark-coloured marine fish, Anoplopoma fimbria, of North American Pacific waters. 

How often have the words coalfish and sablefish occurred in a corpus of books? (source: Google Ngram Viewer )