Simon and The Gate Keeper

The Game keeper catches Simon leaving the vicinity of the fishfarm with a bucket of fish.
"Aha! I've caught you poachin' fish red-handed," says the Game keeper.

"What do you mean, red-handed?" says Simon.
"You've got a bucket full of 'em right there. You can't talk your way out of it this time."
"Oh, you don't understand," says Simon, "I've not poached a thing. These are my pet fish.
I bring 'em to the fishfarm once a week for exercise.
After they've had a good swim, they come back to the bucket and we go back home."
"Do you expect me to believe such a tale?"
"I can prove it." say Simon.
So they walk back to the fishfarm and Simon dips the bucket in,and the fishes swam away.
They stand in silence for 20, 30, 40 minutes...no sign of the fish coming back to the pail.
Ha, you lying rogue! shouts the Game keeper.
"Where are your fish?"
"What fish?"