Most crappie fisheries are harvest oriented. Most anglers, but obviously not all, want to catch crappie to eat. So we try to set minimum length limits to obtain a good balance between fish quality (size) and yield (pounds available for harvest). Based on research in MO and across the country, we know that this balance is typically achieved by setting the length limit close to the average size the crappie attain after three years. So in our southern lakes where fish grow faster, a 10-inch length limit is best. In lakes where crappie grow well, but not as fast, like Truman, a 9-inch length limit is best. But in lakes where fish typically grow slow, like Mark Twain, it is best not to have a length limit at all. Mark Twain crappie, on average across many years, only reach 8 inches after three years. Crappie don't live too long, so protecting slow growing crappie with a length limit could drastically reduce yield while producing only small improvements in size. Mark Twain crappie do grow well in some years and crappie fishing is almost always very good the year after these good growth years. Also, Mark Twain often produces a lot of young crappie, so harvesting small fish is not necessarily bad. In fact, in some years I encourage it.