A fish wouldn’t get caught if it kept its mouth shut.

The earliest located instance appears as an unattributed humorous remark in a Yonkers, New York newspaper column of assorted quips (1891). It was later reprinted in other publications, sometimes embedded in articles or presented as a joke/riddle, which led to occasional attributions to later writers or local personalities who repeated it.

The saying advises that speaking up—especially impulsively or unnecessarily—can create risk or reveal information that leads to trouble, while silence can be protective.

Man is a good deal like a fish. You know, the fish would never get in very serious trouble if it kept its mouth shut.

Even a fish won’t get caught if it keeps its mouth shut.

A man like a fish can generally avoid being caught by keeping his mouth shut.

Consider the fish; he never gets caught so long as he keeps his mouth shut.