Por la boca muere el pez.
Ok let's try again.
NO RESEARCHING PLEASE!!!
Let's see if we can have a bit of fun and get everyone's guesses for this Spanish saying 
If you already know it's meaning how about holding back until others get a chance to guess first.
You can just put your guess or what you think might be an equivalent English saying
9 Answers
Learn when to keep your mouth shut.
I would translate it as "the fish dies by the mouth" as well. Possibly something like our phrase to "stick your foot in your mouth"? My best guess. haha
I don't know what it means, but it reminds me of the saying "en boca cerrada, no entran moscas."
Maybe it has something to do with a fish dying if it breathes air, or maybe it dies by the mouth when it goes after the fisherman's hook. If this is the case, I guess it could either be an admonishment about running ones mouth too much or possibly about eating too much. I don't know though....tough to say. Anyway great expression. I will be anxious to see what the real meaning is
I don't know the answer but I think it's going to be : By the mouth the fish dies. I think it means that what you say can harm you .it doesn't make lots of since but it may work . 
This is making my head spin. I'll try but I'm know I'm wrong:
The fish dies by the mouth.
(that doesn't make sense, I will be watching to see the answer)
Bien hecho todos!
I could have voted for so many but I must give my vote to Megan who put the correct equivalent English phrase.
Podría haber votado a favor de tantos pero tengo que dar mi voto a Megan como ella se le ocurrió la frase correcta Inglés equivalente.
'to put your foot in your mouth'
But all were so good, if you find them interesting I will try to find more obscure proverbs to post later.
Pero todo fue tan bien, si ustedes los encuentran interesantes voy a buscar algunos refranes más alternativo para enviar.
And as well as testing our Spanish we may learn something useful.
Y así como poner a prueba nuestra españoles podemos aprender algo útil
This is obviously an idiom which cannot be translated literally as talking of fish dying/being killed by the mouth would make no sense at all in so much as it would not be a useful phrase to say lol so I would guess it is talking about being quiet/or learning when to talk or be quiet/shut up !
Por la boca muere el pez.
= Know when to be quiet (shut up !)
Yes Marie Claire ... the expressions that springs to mind are:
"Keep your trap (mouth) shut" (Shut your trap ! ? ??) (coll/slang)
and Putting your foot in your mouth
jeje, Maria, I think I got your last question wrong, 
I thought you didn't know the meaning
:::closing my mouth real tight this time::
And this is a clue
Great guesses guys and you're definitely on the right track with the meaning.
Any English sayings that might be equivalent that you can think of?
I'll give you a clue - the English saying also includes the word 'mouth'
