pickerel vs slough shark

pickerel

noun
  • A freshwater fish of the genus Esox. 

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

  • A wading bird, the dunlin. 

slough shark

noun
  • northern pike 

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