Baits or lures are dragged behind a vessel as it moves through the water. With salmon trolling, as many as six wire lines are lowered from the boat, with “cannonballs” (lead balls) holding each wire perpendicular to the hull. Off each trolling wire, as many as 20 leaders, with bait lures attached, are pulled through the water. The main lines are reeled in and out by hydraulic gurdies (spools). Albacore trolling consists of a dozen or so feathered jigs, each on a single line, skimmed along the surface. The advantage of troll-caught fish is quality. One fish is hooked at a time, cleaned and bled, then stored in ice or frozen onboard.