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.
In addition to attaching a lure to the fishing line, an oval piece of metal(often hammered or curved for reflective purposes) called a dodger is often used to attract fish from greater distances. The types of lures used to troll with using dowriggers range from metal "spoons" that are often decorated using color tape, to plastic or rubber "squids" that also vary in color.
The length of fishing line between the downrigger release and the lure is known as the "lead" and this varies in length depending on how far behind the boat the fisherman would like to lure to trail. This fishing line is typically between ten and twenty pound test. When fishing for salmon this lead is often quite lengthy in order to avoid the fish being frightened by the noise of the boat's trolling motor. When many boats are trolling in a small area this often results in crossed lines and tangles which are a detriment to the fishing experience.
The speed at which the lure is pulled through the water has a great impact on success or failure. For this reason fishermen use devices that accurately track speed. Typically, trolling from one to five knots is the range that allows for fish to be caught. This varies from specie to specie as Chinook Salmon may prefer higher speeds while the more docile Lake Trout may prefer a much slower-moving lure. Trolling motors are used to calibrate this speed more accurately than large outboard motors. Trolling plates may be used with larger motors to slow the boat to the desired speed, although some anglers experience mixed results using plates.
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.