Dave D is correct, part of my point is that if you are willing to work and have a pond that lends itself to manual population control, you can make crappie work. My pond is 100 feet out my back door and spend a lot of time there and I work at it hard. I only spend 4 to 10 days a year trapping but I would guess with a larger pond or more spawning area one could easily need to trap more fish to keep them under control.
Regarding traps, I make mine similar to what adirondack describes except mine are just rectangular and I don't use bait. I have some pictures somewhere but I can't seem to find them now. They are 3 feet tall, 4 feet wide, and 3 feet deep. I used a similar plastic mesh, 1/2 inch I believe. I used 1.5 inch pvc pipe to construct the frame. I enclosed the bottom and sides of the "box" with mesh, the top is open, which makes it easy to dump the fish out. I leave the air trapped in the PVC to make sure it floats. On the two largest sides I simply cut round holes (one per side) about 12 inches diameter in the mesh, then I used nylon cable ties to attach entrance funnels that are simply made from the same plastic mesh. The funnels are 12 inches diameter on the large end to match the holes in the sides and whatever size you need on the small end to catch the fish you are going after. My small ends are about 3 inches. I use nylon ties to hold all the mesh together on the frame. The cones are pointed inward toward the inside of the trap so when a fish enters it cannot easily find it's way back out. The cones are long enough to reach about half way across the trap. I attach a tight wire from the small end of each cone accross to the mesh on the other side to keep the cones standing straight out perpendicular to the side they are mounted to. The cones on each side need to be staggered so one does not line up with the other. I simply anchor this trap anywhwere I want. Most of the time I'm setting it in 3 to 5 feet of water so sometimes it sets on the bottom, other times it doesn't quite reach to the bottom. I don't use bait, the fish just swim along and hit the sides, when they try to find a way around the trap some of them end up going into the funnel entrances. You would be surprised how many you can catch this way. Some times I can catch 50 crappie in an hour or two if you find the right spot. This trap works well for crappie and bluegill but I don't think I hardly ever catch a bass. I'll try to find the pictures.
