Mark Twain Lake is an awesome fishery, crappie, channels and flatheads come to my mind whenever I think of this lake. Most all the catfishing is set lines or jugs, where in spring time there is quite a obstacle course of jugs to have to maneuver through. The catfish are all healthy with a lot of hugh channels and flatheads. Flathead fishing is good from the dam all the way up to the tips of the arms, being solitary by nature and in a reservoir setting there is no concentration other than a small one during the spawn, so the only ones taken on rod and reel are usually caught incidental by crappie and bass fisherman. One person I know of has had luck pulling cranks down by the dam area during pre spawn but each year it is hit and miss. Most all flatheads are taken in the upper arms and creek branches during pre spawn period but can be found through out the lake, seems like the upper arms do hold the most or definitely gets the attention.
The upper arms is where folks get the blues, cat in the hat here on the boc has taken some on rod and reel up the north fork, other folks I have crossed paths with on the lake have all taken their blues from the upper arm areas (jugs and setlines). Not a lot of blues are taken on MTL.
Now channels can be caught consistently on rod and reel through out the spring and I might add theres a lot of trophy channels, Ive caught several 9 to 11 pound channels and they are all healthy beautiful fish. For eaters (2 to 3 lbs.) will fish with a minnow under a bobber targeting a wind blown knoll with gradual slop mid way in coves. Evening time right outside the grass or brush line and fishing only about 18 inches deep with light gear and its a blast. During the day will back out deeper and fish around 5 to 7 ft. deep. Worms will get you dinks, minnows will get you eaters and large shiners will get you the large fish. After water temperature reaches low seventies will start fishing on bottom targeting 5 to 12 feet in the evening and morning hours.
Hope this helps.