Dave, I'll take a stab at this one. Why exactly do some fish have spines, anyway? The logical answer might be that the spines make young fish less palatable to large predators. Maybe a predator that has a chance to prey on young fish would choose soft rayed fish like shad first. Shad quite possibly adapted to their lack of spine or other good defense mechanisms with increased fecundity. Why does the white crappie have fewer spines? You got me. Some biological structures are eventually lost over time from lack of use. I think they call them vestiges or vestigial organs. An example of that would be human 3rd molars or "wisdom teeth". As humans have less and less need for large molar surface area to grind raw, whole grains there seems to be a movement towards fewer wisdom teeth. It's not unusual at all for our patients to reach their teen years to find out that they have less than a standard issue of third molars. Three, two, one and sometimes no wizzies at all. It's all speculation, but fun just the same.
In the local lakes around Lincoln, NE the few water bodies that maintain year-around clarity and have good emergent, submergent vegetation systems seem to have predominantly black crappie populations. The reservoirs with agricultural runoff problems and cloudy water are always primarily white crappie. This may not have a huge impact on small water status. One thing that seems to be true is that in small waters with only whites or blacks and good water quality is that the general body condition of blacks seems to exceed that of whites. I'm just really convinced that all other things being equal, in a pond system with no shad and reasonably clear water that black crappie will outperform white crappie over time. If you find me wrong, invite me over and I'll catch out all of the crappie for you.
