Chilean mussel vs blue mussel

Chilean mussel

noun
  • A species of mussel Mytilus chilensis and its edible flesh, native to southern South America and the Kerguelen Islands. 

blue mussel

noun
  • A medium-sized edible mussel, Mytilus edulis, found on the North Atlantic coast of North America, Europe, and in other temperate and polar waters around the world. 

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