fish farm vs trawling

fish farm

noun
  • A place or facility dedicated to the raising of fish or other seafood for sale. 

trawling

noun
  • A commercial fishing technique in which a net is dragged by a moving boat. Not to be confused with trolling, which drags (one or more) lines. 

  • A laborious search. 

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