I am going to throw out some scenarios for consideration.
Fathead Minnows
FHMs are omnivorous, but one of their best assets is that they are efficient at converting primary phytoplankton production into FHM mass.
Would the optimal FHM pond have vertical sides? That shape would minimize any rooted vegetation that would compete for nutrients with the phytoplankton.
Is there an optimal depth? I assume that the growth of filamentous algae (FA) would "steal" some of the nutrients that could have gone into food production for the FHMs AND make the pond more difficult to seine. Is there a bottom depth that would inhibit growth initiation sites for FA? Does that depth change significantly if the forage pond is frequently fertilized and the resultant algal blooms result in significantly less light penetration at depth?
FHMs eat algae, but do they require other inputs to their diet in order to grow rapidly, reach maturity, and spawn successfully? Do they have different dietary needs at different portions of their life cycle? Even if the swimming pool shape was optimal for the production of phytoplankton, is there something farther up the food chain that is even more beneficial to FHMs? If so, what modifications are needed to the forage pond for the best production of FHMs?
Gambusia (Mosquitofish)
Gambusia are not consumers of algae, but instead prefer to consume zooplankton and insect larva. They also like to eat the fry of other fish. Therefore a forage pond optimized for Gams might require significantly different dimensions that one for FHMs.
What would be the best dimensions and pond requirements of a forage pond designed for Gams? I have no idea how to optimize the zooplankton and insect larvae. Would such a forage pond need rooted aquatic vegetation?
Do the Gams benefit by the addition of a forage fish for fry production to feed them? For example, would adding FHMs increase the total annual biomass of useable forage by helping to supply fish fry protein to the Gams? That could result in more/larger Gams AND the mass of the surviving FHMs.
Would a multi-species forage pond be more effective than a monoculture pond?
Forage Plus “Grow-Out Pond (for species such as bluegill or tilapia)
What would be the optimal conditions for a forage pond with a species that requires a more diversified and complicated food chain? Consider the example of a BG forage pond using brooder BG pairs to raise BG to a specific size to then supplement the fishery of a larger pond. That forage pond would require spawning habitat, as well as the means to provide for the dietary needs of BG fry up through the dietary needs of the larger BG and the brooder pairs, plus all the food chain requirements in between.
What vegetation, structure, and surface area would be required to support this more complicated food chain? Would this pond require some 4” deep water with grass for Gams, some larger rooted vegetation to support zooplankton and insect larva, and some fluffy structure to hide minnows from predators and give them a “refuge” to support a population capable of some ongoing reproduction?
How would those requirements change if you were raising tilapia instead of BG?
I think my most unresolved questions concern the depth. What would be the preferred maximum depth and side slopes to achieve the best forage production? (I think the surface dimensions will be largely decided by each person’s local conditions.)
A big “Thanks!” to everyone that chooses to contribute to this discussion! I will try to pop in with more “goals”, or specific situation questions, in the event that there is a lot of expert input and we determine some general principles.
Sincerely,
FishinRod
