OK. So this is just a brainstorm that has been brewing a few months. We all know how well ponds grow fish in the first couple of years. But at some point some things change and the sustainable system, that is, one that has reached capacity and requires support for the reproduction and recruitment of the community members possesses a great deal of inefficiencies to support this need. These inefficiencies revolve around these two main needs.
1. The pond must support prey fish that are too large for the largest predators to eat. These pay their way, of course, by producing offspring that the predators can eat but the system isn't very efficient for a couple of reasons. The adults compete with the young and consume their young. The number of prey fish recruits reaching a length of 1" to 2" is generally quite limited with respect to the potential when the pond is under populated. So growth of predators stall.
2. The pond must support predator recruits. These pay their way, of course, by replacing their parents when they die. But again this isn't very efficient. The predator recruits get the first opportunities of the prey fish reproduction and if they are in sufficient quantity can nearly eliminate any recruitment of prey appropriately sized for the largest predators.
Production of trophy fish is very inefficient for these two reasons. But if one could reduce these inefficiencies the potential for ultimate weights and carrying capacity for trophy fish can be improved. Reduction of the inefficiencies can be accomplished by harvest for example. Another approach has been female only LMB. Both of these work, especially the latter. But there may be one way to greatly improve the latter and that is the topic.
TP are documented to greatly improve LMB growth and carrying capacity particularly in the larger sizes of LMB. One advantage they have is that they disappear every year and this leaves a fresh slate for their niche the following growing season. The efficiency would be greatest if TP reach ideal sizes for the predators but not much larger than that. In this case, the LMB could consume all them if they were so inclined. Limiting the size, also prevents the risk of a Trophy choking on one that is just too large to swallow. This happens ... don't know how frequently ... or if the risk is any greater than with BG.
So in the Female only situation where few LMB are of sizes less than 18" prey becomes desirable at a length of around 3". Below this length prey isn't commonly on the menu and so TP could be stocked in this situation at smaller lengths. So they represent a really good option for forage ponds where they can be produced in very large quantities over several cycles. Probably only the first crop would reproduce substantially (this applies ONLY to Mozambique TP) in the LMB pond after release. Anyway there seems to be a great deal of potential to release a large quantity of small fingerings that can reach a reproductive size by end of the 2nd month in the pond (4" in length) about 1 month subsequent to being the minimum desired length (3"). I've attached a spreadsheet that simulates the attrition of a single stocking but it doesn't also take into account any TP reproduction which would take place after the MOZ TP reach ~4". It assumes all predators exceed 18" in length and that 100% of the fry stocked at lengths of 1" to 1.5" survive to 3" in length. The weight of adult female MOZ TP required to produced this number of fry (6000) in one crop is 3 to 4 lbs. This particular approach has potential to produce 30 lbs/acre of LMB annually while supporting standing weights of 75 to 108 lbs LMB/acre. The management approach is to stock 3 1 year old female LMB annually and harvest 5 year olds with a target weight objective of 10 lbs. I have attached a spread sheet for the LMB as well. The spreadsheets assume 1 surface acre.
The space required to raise this number of 1" TP in one crop is around 400 sq ft.. They could be grown without aeration. For continual production from the adults, the optimum situation would be a rotation of the adults between two or three units. Adults remain in a pond for 21 days, and then are rotated to a new pond by seining with a large mesh. Leaving the adults in the same pond will reduce production because after 21 days the largest fry will be consuming the subsequent crops of newly hatched TP. The spreadsheets explain why a small forage pond can be so beneficial for your predator fish. They provide the conditions to get the YOY to the 1" to 2" sizes in great number.
TP could provide most everything LMB need but there remains a gap following the winter die-off where forage is needed to maintain them until TP fry stocked the following year have attained desirable sizes for the LMB. A possible idea here is a large crawfish species that fills this gap. In the south, red-swamp crayfish may be ideal (if a burrower is acceptable to you) in that they produce a strong fall crop of young that will recycle dead TP not consumed by LMB. They will reach desirable sizes by March and even produce a spring crop also.
I think this scenario could also support a trophy lepomis fishery. In this case, just like the LMB, it would be a put and take proposition where male only BG are stocked on a ladder basis. This would involve adapting the TP stocking such that TP fry are too large for these trophy BG to eat. A reproducing lepomis fishery would undermine the efficiency of this system. I would mention that it really isn't necessary to have a forage pond with TP as forage. One could just stock adults in the spring. The advantage of a forage pond is that there will be very little attrition in growing the fry to the 1" to 2" size. If in the pond, BG will take a toll if they are present and would require a greater weight of adults. So the forage pond is suggested as a way to leverage a small space into a lot of forage.
Last edited by jpsdad; 10/23/2010:21 AM.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
