A tuna fish riddle is:

Q: How do you tune a (tuna) fish?
A: With its scales.

The joke has been cited in print since at least 1916. “You can tune a piano, but you can’t tuna fish” is a related saying.

“Why are fish easy to weigh?"/"They have their own scales!” is a similar fish riddle.


10 August 1916, The Evening Journal (Wilmington, DE), “The Grindstone” by Gene Brown, pg. 5, col. 1:
“I say, Bob, how do you tuna fish. Make him run his scales?”

18 December 1965, The Courier-Journal (Louisville, KY), “Greetings” from Allan M. Trout, pg. 33, col. 1:
DIALOGUE for the day, by Jack Delany, Cincinnati: Wisecracker: “How do you tuna fish?” Piano tuner: “Run up and down its scales.”

Google Groups: rec.humor
_Banjo Jokes_
Darrell Reich
9/19/91
The Canonical List of Banjo Jokes
(...)
(54.) You can tune a banjo but how do you tuna fish?
by adjusting it’s scales…

Google Books
Fishy Riddles
By Katy Hall and Lisa Eisenberg
New York, NY: Puffin
2000
Pg. 44:
How do you tune a fish?
With its scales.

Google Groups: alt.jokes
Funny Signs
Charles Howlett
3/13/00
How do you tune a fish (tunafish)
you adjust it’s scales!!!

Google Groups: alt.humor.puns
Puns of the Weak 09/27/02
Stan Kegel
9/28/02
(...)
You can tune a piano, but how do you tuna fish?
You play on its scales. (Simon Champion)

April 2012, Banjo Newsletter - The 5-String Banjo Magazine (Greensboro, MD), “Kermit the Frog” by Bob Wright, pg. 20, col. 2:
Actually Fozzie has jokes about almost everything. I know his personal favorite is: “You can tune a banjo, but how do you tuna fish?... By adjusting it’s scales”.

Google Books
Sensible Nonsense.. Frank’s Comic Pack:
Humour Pack Series
By Frank Paul
BookBaby
2014
Pg. ?:
How do you tune a fish?With its scales!

Twitter
Lucky Score‏
@LuckyScoreNet
How do you
tune a fish?
With its
scales!
#Joke from #FishingJokes in #Jokes, #Humor and #Satire
12:54 PM - 1 Oct 2017