sterlet vs sturgeon

sterlet

noun
  • A smaller, common Eurasian sturgeon, of the species Acipenser ruthenus. 

sturgeon

noun
  • Any marine or freshwater fish of the family Acipenseridae that are prized for their roe and are endemic to temperate seas and rivers of the northern hemisphere, especially central Eurasia. 

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