When fishing docks for crappie what size line is best to use. Do the crappie stay under the docks all year?

I use 4lb test line 100% of the time while fishing for crappie. Lighter line allows for further casting distance and will let you maintain better contact with your bait, which will help in detecting strikes.

Crappie can be caught around docks year round. The crappie will typically use the shallower docks in the spring and fall months. During the summer and winter months crappie will tend to use the docks positioned in deeper water. 

-Greg Payne
Soddy Custom Tackle