northern pike vs walleye

northern pike

noun

  • A species of pike, Esox lucius. 

walleye

noun

  • A species of gamefish, Sander vitreus, native to the Northern U.S. and Canada with pale, reflective eyes. 

  • One or a pair of sideways-looking misaligned eyes. 

  • An unusually pale eye. 

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