A trolling tandem streamer fly is a style of fishing fly designed to be fished behind a moving boat. Trolling is a form of fishing where the fisherman sits or stands in a moving boat and allows his lure or bait to swim in the water. The Trolling Tandem streamer fly is made of 2 or more hooks tied in "Tandem" or one hook in front of another. Often the hook that is tied to the fishing line is a larger hook.