“Why are fishmongers never generous?”/“Because their business makes them sell-fish.”

A fishmonger riddle is:
 
Q: Why is a fishmonger never generous?
A: Because his business is sell-fish.
 
The “sell-fish”/“selfish” pun has been cited in print since at least 1879.
 
       
Google Books
Entertaining Anecdotes from Every Available Source
Edited by James Baird McClure
Chicago, IL: Rhodes & McClure
1879
Pg. 245:
Why is a fishmonger never generous? Because his business is sell-fish.
 
10 March 1890, St. Joseph’s Daily Herald (St. Joseph, MO), “Conundrum,” pg. 6, col. 5:
Why is a fishmonger never generous?
   
Chronicling America
25 March 1903, The Evening World (New York, NY), “The Old Jokes’ Home” by Roy L. McCardell, pg. 10, col. 3:
Why is a fishmonger never generous?
Because his business makes him sell fish.
 
Google Books
The Games Book for Boys and Girls:
A volume of old and new pastimes
By E Stuart Hardy and Edith Alice Andrews
London, UK: Ernest Nister; New York, NY: E.P. Dutton & Co.
1906
Pg. 123:
Why is a fishmonger never generous? — Because his business makes him sell fish (selfish).
 
Twitter
mmm… and glug…‏
@mmm_newcastle
The daily mmm… food joke - Why are fishmongers never generous? Because their work makes them sell-fish!
1:20 AM - 25 Aug 2010
 
Twitter
Lee Jackson‏
@VictorianLondon
“Why are fishmongers never generous? Because their business makes them sell-fish.”
9:18 AM - 30 Jan 2011
 
Google Books
My Book of Indoor Games
By Clarence Squareman
My Ebook Publishing House,
2016 (Originally published in 1916.—ed.)
Pg. ?:
Why is a fishmonger never generous? Because his business makes him sell fish (selfish).
 
Reddit—Jokes
Why are fishmongers never generous?
submitted August 24, 2017 by Kiyoko504
Because their business makes them sell-fish.