DOWNRIGGER

What is downrigger ?
A downrigger is a device used while fishing using the trolling method, which places a lure at the desired depth. A downrigger consists of a three to six-foot horizontal pole which supports a cannonball (large weight) by a steel cable (generally stainless steel). A clip, also known as a "release" attaches a fishing line to the cannonball weight. The bait or lure is attached to the release.
Brief History
Using a downrigger began in the early 1900’s in effort to increase productivity of fishing in larger bodies of water. One of the more popular models of downriggers is called the "Scotty set up". It was developed by two Canadian west coast fishing innovators named Charlie White and Blayney Scott. They developed this model in the 1970s that used a ten pound weight. It was described as "a good model for finding the right depth at which fish were feeding." Downriggers are used to troll and maintain the lure's depth in accordance with the thermocline at which the fish species being sought normally feeds. People began using downriggers in oceans, while others later developed smaller downrigger systems, which are good for smaller bodies of water such as the Great Lakes. They are now used all over the world and catch a large variety of fish.
In the Great Lakes, downriggers are used to catch a variety of species including Chinook Salmon, Atlantic Salmon, Lake Trout, Brown Trout, Steelhead(Rainbow Trout in the Great Lakes are commonly referred to as Steelhead). Walleye are also frequently fished using outriggers as it is more helpful to have fishing lines extended to either side of the boat for these more jittery fish.