Whistle

A man is walking from the lake carrying two fish in a bucket. He is
approached by the Game Warden who asks him for his fishing license.

The fisherman says to the warden, "I did not catch these fish, they are
my pets. Everyday I come down to the water and whistle and these fish
jump out and I take them around to see the sights only to return them
back to the water at the end of the day."

The warden, not believing him, reminds him that it is illegal to fish
without a license. The fisherman turns to the warden and says, "If you
don't believe me then watch," as he throws the fish back into the water
and then just stands there.

The warden says, "Now whistle."

The guy says, "What for?"

The warden says, "Whistle to the fish and show me that they will come
out of the water."

The fisherman turns to the warden and says, "What fish?"