"Fish Story" joke

(The following appeared recently in the Globe & Mail.)
Forget about Dog Bites Man. Relegate Man Bites Dog to the back pages.
Today we are dealing with Fish swallows dog, an item which reaches us by
way of Moscow.
The dog was swimming across the Pechora River to join its master
when it vanished, leaving only a ripple. The dog's master, who was fishing
at the time, hauled in his net and found it contained a giant pike. He
looked closely at its mouth and said to himself (probably) "Thereby hangs a
tail."
Yes, it was Fido (or the Russian equivalent). The dog struggled out
after the fish was cut open, and, according to Radio Moscow, hurled itself
at the pike, "barking excitedly."
It is often difficult for fishermen to tell stories about the one that
got away. In this case, Radio Moscow notwithstanding, will it be any easier
to tell about the one that didn't?