After a day fishing on Lake Michigan, a fisherman is walking from the pier carrying two brown trout in a bucket. He is approached by a Conservation Officer who asks him for his fishing license.
The fisherman says to the warden, "I was not fishing and I did not catch these browns, they are my pets. Every day I come down to the water and dump these fish into the water and take them for a walk to the end of the pier and back. When I'm ready to go I whistle and they jump back into the bucket and we go home.
The officer 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 trout back into the water. The warden says, "Now whistle to your fish and show me that they will jump out of the water and into the bucket."
The fisherman turns to the officer and says, "What fish?"