Jigging for Lake Trout: Tackle: The Line
There are several things to think about here. Any good low-to-no stretch line will work. Fluorocarbon stretches less than mono, and braid not at all. After fishing with mono for a season I switched to braid and wouldn't reccomend anything else. It is possible to be quite successful with mono or fluoro but as I'll explain braid has them beat.
The thicker the line, the greater the water resistance- this means you lose sensitivity with depth, drag increases, and the jig falls at a slower rate of speed. To jig lakers effectively, you need a fast-falling jig for several reasons. One, you'll spend more time on the bottom where the fish are, and two, lake trout love it! They'll often rocket off the bottom for a fast-falling jig. Braid is much thinner for a given strength. A 15 lb braid has the same diameter as 4-6 lb mono and has much less resistance in the water.
My current setup is 15 lb Powerpro with a 12 lb fluorocarbon leader. A 10 lb leader would be fine as well, as would a mono leader. I usually start with a 10 foot leader and fish my way down to 4-5' before tying on a new one. I start with a longer leader as a little stretch can act as a shock absorber for a hard fighting fish. After a big fight, or if the fish rolled a lot or took the hook deep, check the last two feet of leader for abrasions. I like 100% fluoro P-Line as it's tough and resistant to nicks. I use 12 lb as opposed to 10 lb only because I use the same line for trolling leaders and didn't want to buy two rolls.
Using braid with a leader is an excellent way to maintain contact with your jig, cut down on water drag, and ensure solid gold hookups. The braid has zero stretch, so when you're bouncing your jig off the bottom 100 feet down and a hungry laker grabs it, not only is it easier to feel, but as soon as you lift the rod you are exerting maximum pressure on the hook point. With all mono it will stretch at least a foot and you will have a hard time driving the hook home.
It's a little more expensive to set up your reel, but the braid lasts a long time and you'll bring more trout into the boat. If you don't want to spend the money on braid, I'd reccomend fluorocarbon as it stretches less than mono- but fluoro is also relatively expensive so you're spending similar amounts. The only way this is cost effective is if you use a lot of fluoro for other fishing and have it on hand already. I do not reccomend filling your reel with mono. You may catch fish but your hook-setting power will be greatly reduced and your strike-to-hookup ratio will be poor.