There good reasons why crappie should not be stocked in a small impoundment. Even so, hatcheries produce them and people stock them anyway. Some have success while others fail. I think in most cases, when a BOW owner stocks crappie ... they do so because it ranks above all others to be the fish he wants and that a strong motivation for this is that he likes them for eating.
Let this thread then focus around how BOW owners who are stocking crappie as a preferred fish might ensure he doesn't end up with a pond full of dinks. In my way of thinking, a dink is a fish that is hardly worth the trouble of harvesting. For me, this is a crappie smaller than 6" though many I am sure consider even larger crappie to small too harvest.
A crappie is a fish that is both a forage panfish and a predator depending on its size. They don't tend to reproduce until they attain a size that they become primarily piscivorous and when they do reproduce ... they tend to have an advantage over other YOY due to a combination of mouth gape and earlier hatch dates. Crappie tend to grow faster and larger than lepomis and in as much as this is true have potential to produce a greater harvestable weight of fish annually than lepomis.
Given that crappie are quasi predators, it is an interesting study to consider the scenario where humans and larger crappie work in tandem as the apex predators. In this scenario, the humans harvest crappie that are too large for the predator crappie to eat. The predator crappie do the hard work of cropping small crappie and in so doing reduce the number of them such that those that remain are able to attain a harvestable size by the end of their second summer. The humans thin this class of crappie just as they reach the piscivorous size allowing those that remain to be replacement predators of small crappie. Rather than allowing older crappie to pile up (years w/o harvest), the humans also harvest crappie after they achieve a minimum milestone.
This spreadsheet is an example of such a scenario.
The first line represents annual recruitment of O-year class crappie. The scenario relies on larger crappie consuming enough YOY to restrict recruitment to around 400 individuals. Now this probably isn't practical, the large crappie probably need help from another predator. In any event, given a sufficient number of large piscivorous crappie(but not too many) we may imagine an optimum crappie size structure that is sufficient with the help of humans cropping midsize crappie to be a sustainable production system capable of producing an annual harvest of many midsized crappie and a few large specimens.
To be sure, I wouldn't recommend stocking crappie without a predator. Even so, if one wants to maximize production of crappie he only wants enough additional predation to limit recruitment to the desired level. It is better that these predators consume fish larger than the crappie tend to eat and smaller than the humans are harvesting. Provided the humans do their harvest, the number of predators required need not be large in number or in combined biomass. They need not reproduce provided they are systematically replaced. In fact it is better that they do not reproduce. Furthermore, by consuming fish larger than the piscivorous crappie can eat, the predator doesn't compete heavily with crappie of any size and their contribution is to enhance the production of harvestable sized crappie.
I consider such a system both manageable and sustainable. A key take away for me is that it is important to harvest crappie primarily at the length they are just becoming piscivorous. This maximizes the production of crappie(the weight of harvested fish are largely gained on invertebrates) and it insures that the remaining crappie can grow large and are in good condition to reproduce the following spring (providing a new crop of recruits and forage for the large remaining crappie).
BOW owners who envision a BOW with many large piscivorous crappie have unreasonable expectations. One can sustainably grow a few/acre each year but if he has a pond full of them the situation is untenable. For example, to grow one hundred 1 lb crappie to 1.5 lbs requires 1000 lbs of fish forage. In a 1 acre BOW this is just undoable. If crappie are desired, one needs expectations that are appropriate and he may need to redefine what size of crappie he deems harvestable. An 8" crappie may not be deemed harvestable by some folks and if one is of this bent ... then he must have predators in the BOW that harvest this size crappie or that reduce the number 8" recruits to a very small number (eg ~ 10 to 20 annually).
I think crappie are a doable fish, even in small BOWs ... but we need to understand how to exploit them and not just leave them to their own devices. Some more thoughts on maximizing crappie production . . .
* I think I would avoid _any_ stocking of lepomis. This is not to say that they can't feed large crappie, but you just don't need them. They will compete with crappie and not contribute to their production overall.
* I would also avoid stocking GSH. While these will feed the larger crappie, they will intercept food chain of the smaller crappie which are already efficient utilizers of zooplankton lowering the growth of smaller crappie.
* I would stock locally available minnow species. Where native, I would ensure Gambusia are present and would even consider annual reintroduction. Swingle found that the addition of only 1 lb/acre could increase production of BG by 140 lbs/acre in a fertilized BOW. Quite remarkable indeed.
One last thing. You don't have to know how many crappie are in the BOW. You must know how many fish there should be over 8". Select a number of >8" fish each year and fin clip them. These are reserved until they reach 12 or 13". After these have been selected ... you may harvest any unclipped fish > 8". Take all you can, each year you have another group of 8" fish to crop. Each year you need to select some more >8" crappie to fin clip. Invite your friends if you don't want as many as the BOW will produce, saving them will only undermine the production of crappie. A BOW tends to fill itself with fish, the production will only be determined by the space left by those fish that died. If very little dies, there will be very little production.
