European pollock vs coalfish

European pollock

noun
  • Fish of the species Pollachius pollachius, which live in the Northern Hemisphere, particularly off the coast of Norway and the United Kingdom. 

coalfish

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

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