Actually, contrary to popular belief, I have not seen the overpopulating problem nearly as bad with BCP, I personally fish in a number of ponds that have them and am not aware of a single one, where they are in a mix with LMB, or otherwise actually, that they overpopulate to the point of being stunted.
Now I cant say the same for WCP, I do fish a pond I know of where they overpopulate pretty bad, and also, I think the LMB in that pond have been decimated pretty bad by otters, used to have nice big LMB in it but not anymore.
Like Catscratch said, few things are more fun, or tasty, then trying to thin out a pond with too many BCP in it. and although I've not seen it in BCP, I do know that WCP, after you take a bunch of them out, you will see a definitive difference in size and weight in them in as little as a yr later.
Most of my interactions with crappie have been with the whites. Not in ponds, but in small lakes. For black crappie, the same, in small lakes. These waters supported good populations of crappie in the 7"-9" sizes. I just love this size crappie for fileting. I have caught thousands of them and never threw any back, LOL. Its been a few years since I have had the opportunity to fish for them but my bride really misses them and wants them in our pond.
I've read where crappie need to attain lengths of 10" to reliably spawn. I've also read where they need fish prey to be a significant part of their diet to reach lengths > 10". By the time they reach 10", the majority of the energy must come from fish prey. If abundant, they can grow at good rates of growth beyond that length. Where whites are concerned, I do know they don't have to be 10" to reliably spawn. Where such are very rare, there seemed to be no end to the spawning of WCP in the waters I fished. There were always WCP in sizes ranging from 4" to 10" where the predominant size was in the neighborhood of 8". Now all of these were stunted populations but for a fish that is stunted, an 8" WCP is mighty fine example of good eats. I have never really quite understood why anyone would disdain from harvesting WCP in this size.
One of the things mentioned above ... that is also corroborated by studies of monoculture. Neither WCP nor BCP are as prone to stunting as BG would be. So consider ponds with only BCP or WCP or at least primarily these fish. You have found they supported fish large enough to make the effort to harvest them. Sounds like you keep returning to them year after year to harvest a few messes of crappie. BG could never succeed at doing that on their own. There could be cases where BCP and WCP don't attain such lengths. This in large part depends on the biomass of their parent population when spawned. If the parental population is a major proportion of the carry capacity then their spawns will be mostly consumed by them. There isn't a lot of space for the YOY to grow into and so they grow slow and wind up on the menu ... mostly.
From time to time, I revisit the question of "What is the recipe for a successful crappie pond?" I have also visited the question, "Can WCP be successfully managed to have good balance with LMB in a two species pond?" So my interest in this last question is related to another observation that you mentioned that is also corroborated by the literature. WCP are more reliable spawners. So for and LMB/Crappie combination, wouldn't it make sense that WCP would provide more forage than BCP for LMB to eat? LMB need a good spawning fish to flourish but for fish that only spawn once a year, the biomass needs to be concentrated in fewer LMB. This allows the once a year spawn to produce the number of fish of larger average size that the bigger fewer LMB need. One the other hand, we could consider the opposite, where very few WCP/BCP grow to intermediate lengths that Big LMB need. Such a pond would contain (fewer but larger) crappie and more smaller LMB. Either is a balance that in theory could be achieved by managing the population structure.
So why don't crappie play nice with LMB? I think this is an important question where the answer probably lies with LMB recruitment. In your WCP example above, you noted large LMB in that pond when it produced better WCP and also mentioned you thought the population of large LMB were decimated by otters resulting in an overpopulation of WCP. Not saying that otters didn't do it, but I will also mention that Large LMB are susceptible to mortality due to their age. If they hadn't been replacing themselves, natural mortality may have played an important role in that pond's loss of predators. WCP have decent sized mouths (bigger than BG) and so LMB YOY would be vulnerable to predation by WCP for more extended periods of time. Competition with and predation by WCP YOY probably also play a role. WCP are more inclined to eat fish prey than BCP. So all these things considered, it is possible that LMB are prone to successive years of recruitment failure when combined with WCP. Without recruitment of LMB, WCP will eventually overpopulate without successful recruitment of LMB.
So how could one fight this dynamic as a management strategy? One possible plan is to opt for abundant LMB where the LMB are so abundant that WCP cannot attain large population numbers. Another possible plan is to plan for no LMB recruitment stocking only female LMB and supplementing the lack of recruitment with ladder stocking of female LMB (1-2 lb fish) annually. The idea here would be to have LMB spread evenly across year classes thus buffering natural mortality due to aging. If WCP are better at squashing LMB recruitment than BG, then they may even be a better candidate for the female only strategy than BG would be. Just some interesting thoughts on the matter.
In general, we are discouraged to add crappie to ponds but there probably are ways to very effectively manage them. Would be great to explore this and have some ponds dedicated to these strategies to follow here at PB.
