Pond Boss Forums MANAGING AN EXISTING POND Feeding Would the real FCR please stand up?

In TP grow outs the introduction of a predator can help to reduce competition from recruits thus increasing consumption by the targeted crop of initial stocker TP in mixed sex TP populations. This improves FCR for the targeted crop of TP. This is a paper on TP/LMB polyculture. Each treatment was fed the same rations over a 27 week period. What was different between the treatments, the variable upon which the results depended, was the LMB Density. From their data one can calculate an FCR for the TP target crop. But this FCR describes only fraction of the impact of feed. Other types of FCR one can calculate is for gains of initial stocker TP plus the gain of TP recruits. A total pond ending weight (to include LMB). And an FCR of total pond production including the production of mortalities of TP YOY that were consumed by LMB but are evident in their growth. The estimated FCRs are below:

The optimum FB/P value is dependent upon production goals. If one’s objective is to produce large tilapia and to reduce or eliminate unwanted spawn, bass should be stocked at high density. If bass size is to be maximized, bass should be stocked at low density. The results of this study suggest that a FB/P ratio of 1.4 is adequate for production of large bass. Values near 0.7 would produce large tilapia and minimize spawn.

I'm curious how this could be applied into a pond setting or if there are opinions on that being the correct value as an additional forage base addition to annual stocking numbers.

Boondoggle,

The initial stocking of TP brooders was at 79 lbs/acre with 3 females for each (male) TP. LMB density for treatments 1 through 4 are 20 LMB/AC, 51 LMB/AC, 121 LMB/AC, 262 LMB/AC respectively. So interesting enough, for an LMB/BG combination, a density of 20 LMB/AC is conducive to trophy LMB in moderately productive ponds, 51 LMB/AC is conducive to a balanced fishery in moderately productive ponds, and >100 LMB/AC is conducive to trophy BG fisheries. Here by moderately productive I mean food limited carry around 300 lbs per acre. By and large, even with TP as the forage, the apple doesn't fall far from the tree. Those densities, seem to work to focus growth on either predator or the prey.

I think your question is what ratio of female tilapia to LMB numbers do you need for optimum results. If so, then my short answer is that I do not know. Maybe a good place to start is how much food limited niche is remaining for TP all other things considered. I think a good estimate for that is an additional 75% of carry capacity. So in a pond with 300 lbs/acre food limited carry for the LMB/BG combination. The addition could be estimated at 225 lbs/acre for a total of 525 lbs of fall standing weight all species combined. I would stock a proportion of that 225 lbs/AC as brood. the pond in the study that most productive carried standing weight of 583 lbs/acre TP from an initial stocking of 79 lbs/AC and so the proportion of brood stocking to potential TP standing weight is around 13.5%. So in a pond with 225 lbs/AC of additional TP niche 30 lbs of brood annually may be a good place to start. Keep in mind that they skewed the sex ratio 3 females for every male. Females tend to be 1/2 or less the weight of males and so you might have to buy more than that amount to ensure that the female weight is 15 lbs/AC. You would better off to dispose of excess males as they are not needed and would be a drag on forage recruitment. They could also be reserved for grow out in cages.

We used a limited stocking of 10lbs of 4-7" TP this year, and plan to use again next year as well but the amount we would stock is what I'm trying to figure out. The stocking we did was to both bolster forage (trying to make sure the BG got off good spawns) for the new LMB, and moderate control of FA that we were seeing hints of in the shallows. I'm 100% positive that the LMB won't be able to take out the initial stockers but the spawns from them may be part of the reason we are seeing RW's like we are. Even if I'm wrong, it was a $200 investment so pretty low-cost investment.

I wish I had a forage pond (planned but not implemented), so the TP will have to go in the main BoW. I've seen more stocking rate info for TP as FA control vs forage based additions and those ranges vary greatly.
*** On one of FB Live discussions Mr Lusk mentioned 20lbs per acre, and said he could be convinced to go higher. I wasn't able to ask additional questions on it but my guess is 20lbs per acre would be used in conjunction with some other type of product to control the FA (chemical treating it to knock it down) - I am assuming here and we all know what happens when people assume.
*** In some of the conversations here I've seen FA control mentioned at 40-100lbs per acre.
*** On Forage based applications I've seen rates from 20-60lbs per acre with the stocked TP being in the 4-7" range to minimize being eaten.

Your study seemed to be more in line with forage based applications. I guess the easy part for my application now is that I know the maximum number of LMB that could be present from initial stocking. The math on that is much easier.

In years going forward it gets a little tougher as somehow I would have to quantify the number of LMB present and then do the math on what a minimum would look like.

The results of this study suggest that a FB/P ratio of 1.4 is adequate for production of large bass. Values near 0.7 would produce large tilapia and minimize spawn.

Seems to always come down to forage when looking to grow big fish. Trying to figure out what I need to plan for was where I was going.

Boondoggle,

Are you seeing the tilapia at your feeder? I think most of the people with decent stocking rates do observe them at their feeders - which at least gives you a fleeting glimpse of the current size of the original stockers, and if you had any successful reproduction.

It's really tough for me to identify TP vs BG while they are in the water, but I'm going to say yes and the big TP will follow us around the pond when we hand feed at the different areas of the pond.

Our feeder is on the West bank and we typically take a few cups of food and sprinkle it around the lily/pickerel weed to the North of it. There is a laydown tree in the water NE across the pond of the feeder and we'll sprinkle in some food there as well. Our 3rd stop is Dad's Dream which is on the East side of the peninsula NE corner of the pond. Dad's Dream is as far from the feeder as we can get on the pond. Each of the "zones" has structure/habitat unique to that area.

At all of the zones we can see TP present as the further you get from the feeder the slower the fish are to eat it vs the piranha attack at the feeder (slow slurp from the top vs a quick burst from the bottom to the food and back down. Interestingly the TP typically come in pairs and swim high enough in the water that we can see them coming from across the pond leaving a wake behind them when they figure out there's a snack being delivered. TP do appear more grey in color to me as well vs the BG males yellowish belly but on a quick strike to a pellet from a silverish female vs greyish TP (good luck on that). If I had to guess the large TP are 12-14" and there's a group (100ish) in the 4-6" range that hangs around the feeder. Throughout the pond there are smaller BG/TP that look like the vid link. I haven't trapped these guys yet to confirm but the body shape doesn't look like FHM/GSH to me. Not to leave RES out....BG generically used there.

BG/TP

Tilapia are a great addition Boondoggle. You get much more forage than the initial weight from the brooders and because they consume things the other fish wont ... they feed a greater weight of predators without having to feed them specifically or additionally. That said, they will compete for fish food and you have probably seen some at the feeder.

I like what you said:


I think you nailed the most important piece. Do this first and the rest of what you have to do will be much easier. You are off to a good start. Your initial stockers are not densely populated and this is contributing to the abundance of forage and individual growth. For a pond stocking of 50 in 1.5 acres we are talking roughly 38 to the acre, possibly 19/acre for each sex. I would expect 75% survival +- 5% and so maybe around 14 to 15 LMB/acre of each sex next spring. If you can remove all the males, I can guarantee that you will grow some really big mamas. How big they grow will be determined in part by how much small LMB recruits undermine forage for the big fish. An LMB population highly skewed to females, however, tends to have low recruitment with possible year class failures. Males are the care takers of fertilized eggs and fry. Fewer of them reduces the odds of a large number of recruits in any given year. Your initial stocking is a recipe for success and I think you are going grow some very dandy fish indeed.

When stocking TP it is wise to consider the weight of female TP. A practical rule of thumb is that when the sexes are equally represented, the females will comprise no more than 1/3 of the weight of the stocking. This is important. TP, just like many other fish, produce egg numbers that are highly correlated to body weight. In this sense, the weight of females is more important than the number of them. So the recommendations in that paper do imply stocking TP with comparable initial weights. You should expect that you will need a minimum of 45lbs of TP in order to stock 15 lbs of females. This is if your stocking contains 50% of each. If predominately Male, then you will get less than 15 lbs of females. In the range of treatments you mentioned (up to 60 lbs/acre) the weight of females will never exceed 20 lbs/acre if the ratio of the sexes is 50/50. Please keep in mind, forage production will highly depend on the weight of females brooding among other factors.

You seem really interested Boondoggle and I admire and respect that. If you return to the paper, I will point out some things you may have already noticed. First the predator density was the variable of the first four treatments.

One thing that their data doesn't provide is an estimate of mortality production. You may wonder why that is an important metric ... or as I suspect ... you may have already wondered how much those LMB consumed in each treatment. Dead fish going out the poop chute ... how can one possibly come up with that metric? Since it is non evidence in and of itself ... it can only be inferred from something that is evident. The consumption that would be required to support the growth observed in the LMB. If we restrict the notion of forage production to the weight of forage consumed we would find that the weight of forage consumed was maximized in the treatment that grew the greatest weight of LMB. This was the third treatment. The fourth treatment broke the forage bank, competition for forage was so great that forage was consumed at small sizes. Please keep in mind that the weight of female TP was the same in each treatment and so we should expect the same number of fry leaving the momma TP mouths in all treatments. Doubling the number of LMB from treatment 3 to treatment 4 REDUCED the production of forage by almost 2/3. The primary reason for this reduction of mortality weight was that TP YOY were being consumed at smaller sizes. When I get a chance I'll post of graph of the consumption numbers right below. Now although the production of forage was maximized at a density of 120 ... this is only because the LMB were 4" in length at the time of stocking. If they were 12" at the time of stocking, then density would have to be lower to maximize consumption. For 1 season grow out, the weight of TP stocked could also be reduced.



There was a 5th treatment that introduced another variable. In this treatment the density of LMB/Acre was increased ... but the TP Stocking was tweaked. Although the number of TP stayed constant, the weight of TP was increased to 179 lbs/acre ... or ... 2.26 times the weight stocked in the first 4 treatments. Presumably increasing the production of babies by a similar proportion. The production of LMB very nearly doubled as a result of having larger TP.

Boondoggle, glad to see that you have a forage pond in the works. The advantage of a forage pond is that the uncertainty of producing forage that is too large for BG to consume (or even to large for small LMB) can be largely overcome. With a reduced population of females, it doesn't take a lot of forage fish but they have to survive long enough to reach advantageous sizes. A minimum of 1 times the weight of LMB must survive the winter in sizes that are consumable by large LMB. Large LMB need second year forage and if no 2" to 4" forage survive winter there is already forage shortfall for the largest LMB. At this point in your journey its not a problem. there is plenty of forage to go around.

I find the research very interesting to read and will admit I get lost in some of the information they discuss. It's much easier for me on defined numbers and tougher in year forward thinking for me to wrap my head around. Perhaps in time with a little more reading, pond management or tracking it will be easier to theory craft on what the existing or future populations will be.

It seems the size (in length and quantity per acre) LMB population the defining parameter for stocking rate and size of the TP. Perhaps I'm confused on what the:

The results of this study suggest that a FB/P ratio of 1.4 is adequate for production of large bass. Values near 0.7 would produce large tilapia and minimize spawn.

38 (LMB present)-P x 1.4 (per observations from the study on growing large LMB) = 53+ Female Broodfish-FB

53FB x 2 (mixed sex assumed at a 50/50) stocking. = 106 total TP?

From there it comes down to stocking the right sized TP so there's no predation and a possible fluff for some sort of mortality?

Am I doing this right?

Yes, I think your calculations are good and this would work for you. With Females at .25 lbs and Males at .5 lbs you would be stocking 40 lbs of TP (26.66 lbs/acre) where the female weight is 13.25 lbs (8.83 lbs/acre).

Just keep in mind that the recommendation in the paper was for a 1 season grow out where the pond starts with a clean slate. Your pond will have overwintered BG too. To optimize production of forage, you may benefit from a larger stocking but I would not go higher than your other references state (60 lbs/acre).

That was actually going to be my next question JPS. With the BG, RES, YP, GSH and TP (Forage addition seasonally) how would that impact the TP needs/numbers. Just had to get that early math out of they way before mixing in the other forage if that makes any sense.


I appreciate the help on it for sure.

Boondoggle,

I wish I could help more on that question than I actually can. One thing I can tell you is that standing crops of other predators of TP release fry will reduce recruitment to the sizes that the large LMB need. Just like the forage collapse observed in the paper going from treatment 3 to treatment 4, the egg bank must be large enough to overcome that predation. Too small a TP stocking and the result will be a benefit to only smaller fish. Survival to juvenile sizes are needed to benefit large growing bass. (This is where the forage pond can turn the tide for you.) Anyways, I really liked the 15 lbs/acre of females as a starting place. I do not think recruitment to juvenile sizes would be excessive and it would almost double your TP egg bank.

With regard to your other forage fish, maybe use condition as a guide. I can tell you that if the condition is not good, success at producing juvenile YOY for all species will suffer. The reality is that you probably need less than you may think. If under your feeding regime, condition of brooding sized forage fish fall below 100 RW on average, removing some them will probably benefit the production of forage. In the paper, ~ 48 lbs of female TP were able to produce more than 700 lbs of consumed forage in one season. You need a more modest number of consumed forage than that in your pond in order to meet your goals. One of the reasons the research ponds had such forage production potential was because the starting brood population was well below what the ponds could carry. The ponds were capable of carrying between 800 and 900 lbs of TP at the feed rate implemented. The brood only composed 10% of that weight potential at the start of the season. This left lots of vacuum for YOY to fill. I think managing the adult forage population can be as important as managing the LMB population. I don't understand this other side of coin nearly as well as I would like to. Its much more complicated than managing the LMB population.

I have given more thought to the identification of females and males. Go back to the reference. In the spring leading into and subsequent to the spawn they describe the success of identifying sexes by swollen red papilla where the female is presumed to possess this indicator. It was 90% effective at identifying females and 97% effective at identifying males. So maybes something like 10% of the females won't have it and 3% of the males will (not sure why). But during this time with your current population it gives you these odds. It would be likely that you would remove 2 females mistaking them for male and keeping 1 male mistaking it for female. Those odds don't seem bad and may be practical for you.

Solid advice on the males and female selective culling. Will likely be looking at these guys in the spring to see if they are 1) going to spawn & 2) eyeballing swollen belly female with the right shape/color at the urogenital opening. Definitely to early for me to tell at this point. Not sure I even qualify as a rookie fish squeezer.

I am at a loss how to calculate FCR's of fish in a pond if you don't know (don't have control) of how much they are eating?

Last I checked FCR is (weight of feed/weight of gain). Those gains were all clearly documented along with the daily weights of feed. In fact, that is what that report does well. I gives gains and the weights fed and it controls the weight of feed to be equal between treatments. What we don't have is the control of not feeding. We really do not understand how much gain/loss would have happened if they had not been fed at all. When one thinks about it, the same things making it unclear how much the target crop of stocked brooders actually ate are happening in everyone's pond. It just demonstrates that there are multiple ways to look at gain and conversion. Each is valid in its own context and provides a means of valuing the costs of the entire crop or just parts of it depending on what is marketable by the grower.

I do agree that to understand direct conversion of feed that it is very important to "control" the weight of feed going to group of fish of "known" initial weight over a "known" period of time with "known" ending weight. I would further say that without knowing these one does not have any means of understanding the intrinsic properties of a particular feed.

Imagine the reviewers of the paper above being given as second paper to review. A comparison of two feeds announcing the FCRs achieved by two different feeds but without providing the length of the feeding regimen, the weights fed to each treatment, and the initial and final weights of each treatment. They "might" request this information or they might just reject the paper without giving much of an explanation. But if they requested the information and got no response whatsoever from the remitter (something that is a little like saying "its none of your business") ... its pretty certain that they would reject the paper and not give much credence to the conclusion.