There are two kinds of crappies, and not meaning white and black. Forget the white variety as they're closer to trash fish than being a good fish. I'm talking black crappies being one of two varieties: seriously large and the everyday ho-hum dinks to 10-11" fish. After 11", and put in with the seriously large crappies category, these fish live a whole different world. Since this is in an ice fishing thread, we'll make all references to ice fishing.
Big crappies are big because they play by totally different rules. They tend not to congregate with lesser fish. They seem to be almost solitary, yet they hunt somewhat together. They tend to be selective about the food they chase and eat. When they do hunt, they tend to do so at specific depths. So, what can a guy do to catch some of these brutes?
First, fish waters you know holds very large crappies. Next, get away from crowds. Then forget about having your spot lock focused on the bottom, but rather on that portion of the water column showing the random marks I mentioned earlier. Use baits that seem almost too large.
Don't get too focused on all the activity seen on the bottom. This consists mostly of neutral to negative and small fish with maybe a decent fish or two tossed in, but those larger fish, even if it's a really large crappie, will mostly have very tight lips. The small junk might be teased into hitting a bug or whatever one uses to tease them. The biggest crappies are more like Garfield the Cat and have two life modes: sleeping/resting and eating. They do not dine on the bottom. So don't set the bottom lock for there as you'll miss out on the important information about where they are eating. These big fish use the middle portion of the water column to hunt and eat., so understand that they're not there to pick bugs. They want food. Bugs are like nibbling just because it's there, but that doesn't fill these big suckers up. They have to eat significant food sizes to do that. That food doesn't exist on the bottom. So why target that area? Instead look for random marks at mid-column that appear for a couple seconds then go away and chances are that you'll be looking at larger crappies on the hunt.
These very large crappies are not necessarily solitary fish, but they don't crowd each other either. They seem to have a mutual respect for each other and allow each his own room. Sometimes a bait mass will be encountered where numerous larger crappies will behave much like tuna or sharks and feed en-masse with each other, but this is not a common occurrence. What will be apparent is the use of a seemingly thin band of water, maybe inches yet maybe a couple of feet. Water temperature, prey, light penetration.... there can a myriad of reasons these large fish use such a narrow band to feed, but they do and do so only if there is real food there. If one wants to use spot lock, put the marks smack in the center of that box.
One of the surest ways to entertain these larger fish is to use significantly larger baits. Z-Vibers, Jigging Rapalas, regular ball-head jigs
with plastics in the 1" to 2" range
or even 2' plus minnows if you need them are all legitimate bait sizes for these fish. If you are keeping a few of these big dudes to eat, check out the stomach contents and you may get an eye opener as to the size of what they've been eating. I, in the past, have regularly found these big crappies with 2" sunfish up to 4" perch in the guts.... in the dead of winter yet.
As always in the winter, things can change from day to day or even hour to hour. Most often it is a change surround the barometer and if anyone thinks that the fish are not closely in tune with the barometer, think again. The barometer in the winter is like a thermostat in your house. There's a comfort level with the fish that is controlled by the barometer. Move that unseen dial up or down and see what the crappies do in answer to the move. Often times if the barometer is on the move the fish move with it so if you lose touch with the fish, change something, especially where you're looking for fish in the water column and maybe start to down-size the baits or slow down the presentation. These big crappies can be quick to make adjustments which means you have to be able to notice these changes and follow suite.
I regularly fish in the dark and use two bobber stops on my line: one to keep the depth and the other about three feet above the jig so I can't reel the float up and bang the tip top when I can't see well. I leave it that way even in the light. I've had people around me see that when I reel up, then go back and set their floats at three feet thinking that's my depth even though we were sitting over 30 some odd feet of water. What really amazes them is when they have one of these huge old crappies come along and almost pull their arm down the hole while fishing that shallow.
There are crappies and there are big crappies. And if you want the latter, best you forget all of the stuff you learned to catch the so-so crappies because the big ones are big for a reason and the small fish did not teach them.