During the trolling off season is a good time to go through all of your leaders and replace many if not all of them that have been pretty well chewed up from the prior season. Making the correct selection in terms of actual leader size for your setup is important, and here are a few tips from Blood Run Tackle Pro Staff.
Flat line leaders. If you are fishing early season browns (not coho's), a 15lb test fluorocarbon if the water is gin clear is a very good choice. Browns can be leader shy and smaller makes a difference here. However, in many ports in early spring, we mostly target Brown Trout in river plumes or between sandbars where the water is stirred up...which is why we prefer to go with a 20lb test fluorocarbon leader.
The reason is simple. First, we can get away with a bigger leader because of the stained water, and second, we most likely will get into some Coho, and when those Coho barrel roll themselves up into your flatline leader you want as much material as you can get away with.
Once we move past spring time fishing and look at when we may most likely use our flatlines, which would be offshore scumline fishing for Steelhead, or in front of the piers when the lake rolls over, we go straight up to 30lb fluorocarbon leader. Steelhead hit hard, and frequently jump and twist...a larger diameter material is helpful here. In addition, at some point we will be back in front of the pier heads to try and catch some kings when conditions are right, and 30lb test is a bullet proof leader size for those conditions.
Diver Leaders. We follow a similar progression as we do with flatline leaders, starting off in the 15-20lb range in early spring and then quickly move to our standard 30lb leader once we hear of Kings being caught. Throughout much of the spring and early summer, 30lb Fluorocarbon Leader is more than sufficient for Kings and Steelhead that are roaming around. We do however make a jump up to 40lb test Fluorocarbon when we believe the arrival of Kings in strong numbers is becoming close. We are starting to pull almost an exclusive paddle/flasher program with Meat Rigs or Flies at this time. For whatever reason when the water gets hot (up into the 70's) and the Kings are coming in, along with larger Coho, the 30lb Fluorocarbon leader just does not seem to be quite large enough to handle all of that expensive tackle plus a large hard hitting King. 40lb Fluorocarbon is the only leader we recommend using on our divers when we switch to our flasher program.
Copper/Leadcore Leaders. You can go either way here early in the spring with short coppers like 35-50 feet or 1-3 color lead. Some guys like 20lb for maybe some more stealth in clear water. We run a mix of 20lb and 30lb depending on what bait we are pulling, and then quickly switch right over to 30lb Fluorocarbon on our copper leaders for the remainder of the season. 30lb Fluorocarbon in anywhere from a 30-50 foot section off a copper setup is the ideal leader setup for anything you might hook up with. We rarely if ever have to replace our copper leaders once we switch them over to all 30lb, that is truly indestructible material for copper setups, particularly when "mining" for lake trout or walleye.
Flies & Meat Rigs. Pretty standard here. 40lb Fluorocarbon Leader for trolling flies. 50lb Fluorocarbon Leader for Coho p-nut Flies, and 50lb Fluorocarbon Leader for Meat Rigs. Pay particularly close attention to your knots on these different sized leaders, please refer to this article for a breakdown of proper knots when using Fluorocarbon for such connections.