Pond Boss Forums MANAGING AN EXISTING POND Feeding LMB Are Remarkable Converters of Fish

I came across this little gem of a 55 year old paper some time ago but only recently have had the time to do a thorough review. I am posting in part to answer esshup's question with regard to assimilation of foods eaten. In the case of this paper, the foods are live food where the predator is LMB and the prey is GAM. All the same, the principles of bioenergetics are laid out very well and I have learned a lot from this study. Below is a graph of the bioenergetic use of consumed energy. They converted fish mass into energy content and so presumably we could substitute prey of varying energy density to arrive at estimates of conversion for these prey as well.

I guess we can't upload images any more through the document manager? (OK so I was able to share a link to the image at Google Drive but the image address doesn't work with the UBB image tags. If anyone has learned how to embed Google Drive images with UBB forums, please share how and thank you in advance!)

[img]https://drive.google.com/file/d/1tK33-qBfrUcRsgJgxNS6KcMwtE9zi5yr/view?usp=share_link[/img]




In their analysis, assimilation is the amount of energy LMB can extract from consumption for both growth and metabolism (respiration). In earlier posts, I spoke of assimilation as the growth piece treating assimilation as the nutrients retained (not expelled as waste and/or used for metabolism). Since the authors are speaking of assimilation in the accepted definition of bioenergetics, I will correct my earlier mis-definition. Another way of describing assimilation is the digestibility of food. So in the case of GAMs, LMB are able to digest between 73 to 80% of the energy they consume. The assimilation/digestibility depends on the rate of consumption. This may deal with retention time in the gut. The assimilation efficiency is limited to 80% but will decline the more an LMB consumes. The curve of respiration is the metabolic use of consumed energy. If the respiration is subtracted from the assimilation what remains is the growth of LMB.

I digitized the curves of assimilation and respiration so they could be tabulated in excel. From this information I was able to calculate wet weight and dry weight conversion of GAM consumption to LMB wet weight growth. There were some interesting numbers that arose from the analysis. The curves demonstrate that there are two things working against gain conversion. The first is respiration. The metabolic requirement must be met before any gain can be made. The metabolic requirement is not large but as consumption increases, metabolic demand also increases. Of interest, it is a geometric relationship that diminishes growth conversion efficiency at higher consumption rates. The second is assimilation. Assimilation also follows a geometric relationship at higher consumption but the relationship is inverse (IOWs assimilation as a proportion of consumption declines as consumption increases). In combination, growth conversion efficiency is most efficient at a wet weight consumption of 6% of body weight per day of GAMs. This translates to dry weight consumption of 1.6% of body weight per day. At higher wet consumption rates, conversion efficiency worsens. Now although efficiency declines above 6% wet weight the conversion is still excellent. At peak conversion efficiency, LMB add 74% of the wet weight GAMs consumed to their own wet weight. It speaks to the high nutritional properties of GAMs which are substantially more energy dense than the LMB are on a wet weight basis. Here are few take-aways.

1. LMB convert fish extremely well.

2. The wet weight consumption for maintenance is around 1% of body weight per day. Adjusted for the energy density of BG, LMB require 1.36% of their body each day to meet the respiration/metabolism requirement. Multiplied by 365 days this translates to 3.65 lbs/year of GAM or 4.97 lbs/year of BG.

3. The wet weight FCR for GAMs at 6% wet weight consumption is 1.35. This is better than the conversion of many feeds which are fed dry. If the we calculate FCR on a dry weight basis (1.6% of body weight), the FCR is .36. This is just an amazing number that speaks to the digestibility of fish meal. Consider for example a formulated feed with an FCR of 2 at the dry weight consumption of 1.6 % of body weight per day. Such a feed need only contain 18% fish meal. Everything else could be inert providing no additional nutrition. Such a feed would only contain around 12% protein by weight. Most of the protein in typical formulated feeds is definitely not fish based or the conversion would be better. The exception to this would be feed formulated for fry. Now there is a lot more to feed than just fish meal. For example, it has to float, be thrown from a feeder, be affordable, and be economical for production. All of these will diminish how much fish meal goes into a feed and so a 100% fish meal feed is not practical and I would not want this to be construed in this way. Even so, IMHO, the quality of any formulated feed as it relates to LMB and possibly BG may well be a function of the percentage of its weight that is fish meal or other animal by products.

4. GAMs are a high quality forage for fish up to about 1 lb. Very energy dense and comparable to trout and shad. The dry weight percentage of GAM is 26.58%. The dry weight of GAM is divided 56.5% protein, 25.27 % lipid, 18.53% ash. In the wild GAMs average 10% growth by weight every day and have attained growth rates as high as 20% of body weigh per day under laboratory conditions of ad libitum natural foods. The high rate of growth and reproduction explains how small standing weights of GAMs can produce substantial forage contributions. It is not clear what weight of GAMs were produced in Swingle's treatments. But the difference in the gain of BG could be explained by an increase in forage equivalent to 200 lbs of GAM/acre (Additional consumed energy that would be derived from 200 lbs of GAMs). Given that GAMs compete with BG, at least this much GAM forage was produced and this fact is made all the more remarkable in that they were produced from an introduction of only 1 lb/acre. Even a small standing weight of GAMs can produce substantial forage. If a pond were to support a 40 lb/acre of GAM by early July, for example, it would produce a minimum of 4 lbs/acre of GAM per day for the remainder of the reproductive/growing season. This is equivalent to 1.06 dry weight of Gam every day. Relative to a feed that converts at 2, over a 90 day period, this has an equivalent feed value for growth that translates to feeding rate of 5 lbs/acre/day. Over 90 days, this translates to $450 of feed at a feed cost of $1/lb.

5. The maintenance requirement for fish need not come entirely from protein. One of the things that spoke to me in the analysis is that formulated feed does a better job of maintaining LMB and BG than it does in helping them gain (relative to dried fish). After some thought, the only explanation I could deduce is that LMB and BG can assimilate lipids better than they can the proteins in formulated feeds. Protein is essential for growth and the mix of proteins in formulated feed is ... overall ... inferior to fish meal. But lipids, whether fish based or not, must possess proportionally higher digestibility than plant based protein. Bio-modification of plant proteins however may change that. But for now it is clear the quality for maintenance in relation to the quality for growth are two different things in formulated feeds where growth quality is correlated to the content of fish/animal based proteins.

6. After the first year, most of the forage production in recreational ponds goes to maintenance and then trends toward being unable to provide maintenance. Also any day a fish goes without consuming maintenance is a day the fish lost some weight.

Thanks for doing the work, jpsdad! We so often overlook past research because it happened years ago, a sort of chronological snobbery that fallaciously assumes recency equals quality. Well done.

It will take several more readings for me to "assimilate" all the data, but one immediate conclusion is that artificial fish food, even with good levels of fish meal, is not a perfect substitute for the real thing, at least for LMB. Valuable supplement, but not a replacement if growth is to be maximized. The fishy food chain must be maintained! I do wonder if similar conclusions would be true of BG, HSB, and RBT.

But what about the calories expended to catch the prey, such as GAMs? Floating pellets don't require much effort to consume, which I always thought was a big advantage.

You're most welcome, Frank.


I agree that the food chain must be primary source of nutrition to have healthy fish. Formulated feed provides supplement and even if it were only sufficient for maintenance, this allows conversion of the additional food chain consumption at optimum conversion. Frank, I will also mention that the intrinsic FCR of GAM dry weight is .29. So in a case where formulated feed provides maintenance, GAMs convert wet weight/wet weight LMB at 1.09 to 1. Dang near 1 to 1 on a wet weight basis. IOWs feeding can help fish convert what they are consuming in natural foods much better (not to mention that feed wastes help feed natural food organisms). But keep in mind that GAMs have a greater dry weight percentage than LMB do. Carp and koi forage converts below 1 to 1 if the maintenance is provided by supplemental feeding.


Different species of fish have differing nutritional properties themselves. We must keep in mind that some species are much more energy dense than others. For example RBT are substantially more energy dense than LMB. Wet weight energy density of RBT is 38% greater than LMB. This means that RBT must retain 38% more energy than an LMB to gain the same wet weight. Yet RBT will convert much better than LMB when both are fed a salmonid diet. One of the reasons is because of the nutritional profile of RBT in which lipids are a substantial proportion of their own energy content. Usually, fish that naturally that have higher lipid weight percentages metabolize carbohydrates better. This is why RBT and HSB will convert better than LMB. They convert some of the carbs to lipids (just like we humans also do). Based on conversion efficiency, my sense is that LMB (and to a lesser degree BG) do not assimilate carbs well. This gives RBT, HSB, and CC an advantage over BG and LMB when using feeds that use starchy ingredients to bind feed.

All that said. LMB and BG (I presume) are very efficient converters of food that is predominately animal protein and lipids. Lets say we produced a wet feed using only fish meal and gelatin as a binder. If the assimilation of energy consumed(respiration + growth) were similar in RBT and HSB (maxing at 80% near maintenance and minimizing near maximum consumption around 73%) then I think we would find that RBT and HSB have no advantage at converting but are essentially equivalent on a food weight/energy gain basis. The lower energy density of LMB would necessarily mean that they would be better converters at equivalent feeding rates when conversion is a wet weight gain metric.


Frank, I was very surprised at how little additional energy it takes to consume the maximum consumption. Based on their findings, LMB tend to max daily consumption of GAM at around 12.5% of the LMB's own energy content. At this consumption rate, an LMB expends around 2.8% of its internal energy content daily for metabolism (which includes chasing down GAMs). Now keep in mind that an LMB needs to consume 1.33% of its own energy content daily as a maintenance ration (no daily gain). This is the minimum maintenance at 20C and temperature actually does not affect the minimum metabolism requirements as much as one might expect. Even in cold water fish have a metabolic requirement that comes from feeding at lower rates of consumption and/or at the expense of their body mass. OK, but back to your question. To consume GAMs equivalent to 12.5% of its internal energy content requires an additional 1.47% investment in metabolism above maintenance. Trade off for consumption after maintenance is a return of (12.5-1)/1.47 or 7.82 parts of consumption above maintenance for the additional metabolic investment. For the economics of growth. If an LMB consumes 12.5% of its own energy content daily it will gain 6.34% of its own energy content daily. The trade off for gain after the additional metabolic investment is (6.34)/1.47 or 4.51. That is a 451% daily return on the energy investment of consuming above maintenance. I like to relate the investment of feeding above maintenance because a fish that doesn't eat its maintenance ration will shrivel and prematurely die. Even with GAMs the investment of chasing down prey seems very worthwhile.

One thing that jumps out at me is the age of the study (55 years) and the light years that the fish food industry has changed.

What was the length of those LMB? Weight was from 0.716g to 19.24g.

How does the caloric content of a gam compare to a BG? Since Gams are a very small fish (common length average is 3.9 cm) they would only fit in a narrow window of a LMB lifespan as optimal feed. (4.5" - 8.25" in length)

Since they dried the fish to weigh them, we'd need to add water back to the fish to see how they compare to artificial feed since the LMB aren't eating dried fish.

Good points. While I'd be willing to bet that larger LMB still benefit more from a natural diet of Shad, Bluegill, and rainbow trout than any amount of feed, there's no denying that the fish food of today is far superior to yesteryear.

The age of study doesn't bother me esshup and here is why. I figure that LMB in 2023 convert GAMs pretty much the same as they did in 1968. So I am agreeable to trust it. Also, I figure that the Dry Weight percentages and energy content of GAMs hasn't changed over the same period. The study didn't make any comparisons to or use any formulated feed. I made those comparisons from recent determinations of FCR which were posted here at pond boss where the feed rate was 3% of body weight. Since I was comparing that FCR to GAM dry weight consumption at 1.6% of body weight, the comparison was very generous to formulated feed.



The LMB were small. I was concerned about this as well but the study normalized consumption on an energy basis related to the energy content of the LMB. In other words, it didn't depend on length of the LMB. Now one might "say" that length matters in terms of assimilation (efficiency of digestible energy) and respiration (metabolism) but I tested this hypothesis and here is how I did that. I calculated the annual maintenance ration ... and even though the LMB were small they required 3.65 lbs of GAM annually for maintenance. I converted this ration to BG by taken the product of the this ration with the ratio of GAMs to BG wet weight energy density. The energy density of BG is 4186 J/g while the energy density of GAMs is 5567 J/g. This means it takes (5567/4186)= 1.33 times more wet weight BG or 1.33*3.65 (4.85) or roughly 5 lbs of BG to support 1lb of LMB. This true of small LMB and if we can agree that larger LMB require ~5 lbs of BG for annual maintenance, then its very hard to argue that larger LMB use consumed energy differently than the smaller ones the study used. This is the beauty of normalizing metrics. It isolates the simplest and most elegant principles of nature.

What changes at different LMB sizes is consumption. You can't get a 1lb LMB to consume 6% of its body weight in wet weight prey everyday. They just will not consume that much. If a 1 gram LMB Fry consumes 6 % of its body weight daily in wet weight GAMs for 90 days it would grow from 1 gram to 85 grams (>7") over the same period. Some LMB are capable of this consumption but it is too rosy for most. Even for those that grow from 2" to 7" in 90 days the consumption wouldn't be a constant 6% but probably more like 9% at 2" and 3% at 7". Consumption as a proportion of weight varies among individuals where the fastest growth is obtained by the individuals that consume the most.


Sure, I wasn't saying you could feed 5 lb bass with GAMs. But I don't see why 12" LMB wouldn't consume a 2" GAM. Indeed, I have witnessed this happen. The caloric content of GAMs on a wet weight basis is 1.4 times that of BG. Swingle tested GAMs with LMB and averaged 153 lbs/acre of LMB over 1 years. Such standing weights were not achievable with BG and obviously many of the LMB that grew on GAMs exceeded 12" in length. What about 10" BG? A 10" BG weighs 1 lb. Is a 2" GAM something it would consume? Its all about availability and capability. The bio-energetic studies I have seen suggest that lower limit of consumption by piscivores is around 1/1000 the body weight of the predator. Hypothetically a 2" GAM might be consumed by a predator as large as 1760 grams. For 1lb LMB the ratio is 1/257. If adjusted for BG caloric equivalence the ratio is 1/184. Though a 2" GAM is not ideal prey for a 12" 1 lb LMB, it provides enough energy to be worth while. Five 2" GAMs are 1.94% percent the wet weight of a 1 lb LMB. Per the findings of the study, the 1lb LMB can gain on that ration only requiring 1% of wet weight for maintenance. The gross wet weight FCR at this ration is 2.4 and corresponds with a specific growth rate of 0.815 % daily. Not a lot but enough to grow a 1lb bass from 1 lb to 1.25 lbs in 4 weeks. So does it make sense for 1 lb LMB to eat 2" GAMs? Of course it does. Again it's about availability and opportunity.


No. Not so. The caloric content of both LMB and prey were estimated from known wet weight conversions. All of their data is represented in the metrics of bioenergetics (energy). I converted these metrics to wet and dry weights so the comparisons could be made.

Probably the most scholarly document I’ve read here. And, I’m still rereading it.

Now we just have to find a pond that is loaded with Gams and no other fish to test it out.

You read my mind!

One of my experiments this year was to try over-wintering some fish to determine how much I would have to upgrade equipment to be successful.

Gams kept in an unaerated little beta fish tank and fed fish flakes - SURVIVED!

Gams kept in a 40-gallon aerated tank with two pellet-fed yellow bullheads - DECEASED! (And mysteriously disappeared.)

I still plan to try and build a few new ponds at my place when we can get ahead on the family budget. I think I will try a gams experiment instead of FHM as the starting forage on one of the ponds.

Unfortunately, based on the rains of the last three years at my place, then a dune buggy race track may be the only feasible recreational project.

Hopefully the recent switch from La Nina to El Nino Pacific conditions will bring you more rain, Rod. You might be able to drill a well, but that's expensive and the water isn't always best for ponds.

Thanks for the hopeful wishes! (I probably should have left out the drought complaint in my post above, I was really just reporting how easy it is to keep gams! I was a little peeved that the state had good rains yesterday, and there is a big dry area centered around my farm.)

Many areas of Kansas are "oversubscribed" for water rights. Basically, we can direct surface flow of water into a pond, but are not allowed to pump groundwater to fill a pond - unless you have a senior water right.

Who knows, the drought may turn out to be a net benefit. The subsoil water that sits on our clay horizon was always going to complicate construction efforts. Maybe if I could get started this fall, then the dry ground could make life easier!

Wow, Rod, I didn't know Kansas had such stringent rationing on groundwater. I guess that makes sense, as you want to preserve the aquifer, but it stinks during a drought.

Are you actively farming and/or ranching on your land, or is it more of a place for recreation?

Rod, does Kansas allow irrigation for farmers?

Yes, we have 100 acres of dry land wheat planted in most years. The modern cultivars are damned impressive! Our average rainfall is about 30" per year, but we have been in a persistent drought and our creek quit running this fall. Yet we still planted winter wheat in October.

It is still so dry at our place that I have poison ivy along our barbed wire fence lines in full sun that has not yet leafed out. However, the wheat managed to access every bit of soil moisture and looks decent!

We also have 115 acres of native tall grass prairie that a neighbor cuts and bales for his cattle. It is greening up, but is very short for this date. I think the survival trait of those grasses is to barely grow during a drought and to retain energy in the deep roots and just wait for when the rains finally come.

We did get 0.45 inches last night, so that should help all of our various plants!

Yes on the irrigation.

I am not an expert on our complex water rules - so I am sure I will mis-state some facts in my explanation. (Snipe knows the rules since he had to jump through many hoops but managed to get some extra water for his operations.)

I believe most of the water rights were developed on a variation of "first come, first served" basis. If you had a great aquifer under your farm, you could physically pull as much water as your crops could use. This amount was reported to the state for several years, and then you eventually "perfected" a water right for roughly that amount.

However, in the 1970s (?) we realized that the water levels in the aquifers were going down and the recharge rate was much less than the water usage rates.

I inquired about a water well on our farm for supplementing our ponds. The answer was a firm no! Our area is oversubscribed for water appropriations. I believe if the conditions get bad enough, the state can shut down some of the more recently granted water appropriations to allow the most "senior" rights to draw their full allocations.

We do have good exceptions though. I can drill a well at my farm for "household" use. The allocation is enough for a family, plus watering some trees and/or lawn and raising some stock animals. However, NOT enough for a commercial hog operation, or filling ponds, etc.

I am sure it is not the optimal system, but the law on matters like that always grows organically.

I think most of the western 2/3rds of the state is in a similar circumstance where the aquifer is drawing down. However, the Ogallala Aquifer is a geologic marvel. It extends from South Dakota to west Texas. There are places in Kansas where it is 500' thick. There are places in Nebraska where it is over 1,000' thick. The largest available well pumps could not even draw down the water levels an inch (in the short term) in places like that. I suspect the farmers thought that they had a limitless supply!

The eastern third of Kansas gets significantly more rain, and has many areas with rock outcrops rather than deep prairie soils. (snrub farmed in eastern Kansas and has pictures of his place in some of his posts. However, I suspect it is not far to bedrock beneath his fields.) There are even places with some moderate sandstone outcrops that look very similar to Anthropic's property - except the forest is Post Oaks instead of pines! We do have a few areas of pine forest that look like parts of East Texas, but the subsoils have to be exactly right.

Glad to hear you got some rain! That your cultivars survive severe drought is remarkable, and encouraging. I always get a chuckle about how some folks rant & rave about GMO crops, not realizing how much we depend on that, whether by crossbreeding or genetic engineering. Heck, we pondmeisters do the same when we buy HSB, HBG, Tiger Muskie, or Tiger Bass!

Also, your crop probably benefits from rising atmospheric CO2 levels. It's well established that most plants need to open their stoma less in CO2 enriched environments, thus losing less water to evaporation. One reason why the deserts are greening.

If I get a good rain in September, I’ll plant wheat for deer. It helps get them through winter and gives me a couple places to hunt.

Providing the hogs don't eat it all before the deer get a taste of it.

Scott, the dang hogs have apparently left. No tracks, no sightings and last week I loaded my Judge with .410 shells. Then eased back into,the area where they always slept during daytime. Gone. The boys put up cams at feeders and no hogs.

Ours moved out for a while but are back now. Bout the only good thing about them is they will put a hurt on the copperhead population…. Those are nasty lil fellers

Pat, I had a lot of snakes that the hogs pretty well cleaned out.

FishingRod, interesting thought. It may be that FHM stocked in March before BG and LMB might produce more but I am sure that GAM would perform well, particularly considering that you mentioned this year's first cohort a couple of weeks ago(earlier than I thought for KS). If you have weeds or brush I think the Gams would over-winter and produce limited forage year after year with a classic LMB-BG combination. I base this on the fact that many of the ponds near me have populations that sustain year after year in the presence of LMB and/or BG. The degree of the GAM population depends on cover, at least this has been my experience. FHM will go away and GAM might go away but GAM stand a pretty good chance of hanging around.

In Swingle's treatments he tried GAM as the sole fish prey for both BG and LMB. He reported the GAMs essentially extirpated in both cases. I will be quick to say that his ponds were probably not very weedy (being under fertilization to maintain bloom) and the sides were probably steeper than a typical rec pond. IOWs there was probably not much cover for them. I've always wondered what stocking rates he tried (but didn't note) but I do think that the ones he reported in his work on production were stocking rates that optimized production.

I have tried to more deeply understand the predator-prey interactions of his GAM combos and worked up a simulation to see if I could replicate the results with a model simulation. I have had varying degrees of success but I think the model is pretty close. In a optimal system, all of the food is eaten at just the right time. If consumed too early, the predators begin to decline. It seems to go without saying that fish will eat all they can (if they care too). By this I mean they will eat as much as they able to up to the limit that they can consume. The limit changes with age. What differentiates fish that grow really large is that they have higher rates of consumption. BG could in theory grow as large as LMB if they would consume as much and live as long. So in modeling BG I did modify the consumption (related to maximum growth rates) to be a fraction of LMB consumption. Below is an image of the BG treatment of Swingle in simulation.

Swingle BG-GAM

I will mention that the simulation is very sensitive the consumption ratio and the stocking density of the BG. If they were as hungry as LMB, 1530 of them would extirpate the GAM in short order. Also, if the number of BG were doubled, the same would happen impacting the results adversely. The same is true of the LMB. GAM cannot sustain a large population (number of individuals). Below is an LMB simulation. Now Swingle's treatment was for a year instead of only 6 months in my simulation. But his standing crop at 1 year was substantially larger which means that they must have continued growing and probably recruited. In a pond with no cover, this finished off the GAM. But not until after they had gained 172 lbs. The stocking rate is 100 2" LMB and 1 lb of Gam to the acre. With 70% survival, neglecting the weight of recruits, the average weight would have been 2.45 lbs and with 100% survival 1.72 lbs. Whatever the case, it is safe assume that it was probably somewhere between those two numbers. LMB are thought to grow maximally up to 2 lbs in their first year and so this seems to suggest GAMs were capable of growing the LMB at close to the maximum in the first year. The image of the LMB treatment (first 6 months) in simulation is below.

Swingle LMB-GAM

So a few things I learned from the exercise.

1. Stocking rates matter. You can't double the stocking rate without extirpating the GAM food source and destroying a good thing.

2. The size of fish matters. For example. 100 lbs of 1/10 lb predators consume a much greater percentage of their body weight than 100 lbs of 1 lb or 2 lb predators do.

3. What #2 means is that there are standing weights of adult predators where GAM could provide all of the forage needed ... PROVIDED ... the predators were unable to reproduce AND the predators are cropped reasonably. Throw in predator reproduction and the GAMs will not achieve their potential.

The simulations suggest that GAMS can sustain consumption rates of between 400 to 500 lbs annually in fertilized water. When the population of predators WANTS to consume more than this ... they will extirpate the GAMs. To use GAMs as "the" prey species requires predator consumption of GAMs below this number. This means fewer larger fish can live in harmony with GAMs provided they are growing maximally ... eating all they want... and where GAM reproduction can keep pace.

GAM can certainly produce more than 400 lbs of forage annually. One reference noted 800 pounds of production per acre-year in fertile water and no feeding. In this particular case the GAM were harvested periodically through the growing season to prevent fish kills. It is cropping like this that can substantially increase the productivity. The removal of GAMs, whether by netting in this example or by predators allows GAMs to grow maximally and reproduce. The same is true of any prey fish ... so nothing really new there. GAMs, like other prey fish, can produce more than their limiting standing weight every year provided they are cropped so as to prevent them from reaching that limit.

One particular combination that seemed to have potential to me is HSB-GAM where HSB are stocked on a 25/year ladder. Below is the result of that simulation and it suggests that one needs to overwinter a minimum 25 lbs of GAMs to sustain the population. The scenario requires annual harvest of 3rd year fish. Assuming 100% harvest of this age fish, the HSB population would not be able to keep up with GAM production. The scenario allows a harvest of an estimated ~82 pounds annually of fish in the 18"-20" class. GAMs may not be the best forage for the 3rd year fish (they need the biggest GAMs) but HSB do seem a really good candidate because they can be supplemented with a little feed. Here is the image of the HSB simulation.

Possible HSB ?

Here is an image of the weights of the ladder stocked fish where 1.2 lbs of growth is assumed each year. This particular growth corresponds with maximum consumption relative to LMB of 0.81. If HSB would consume as much as or more than LMB, they may need to be reduced in number or satiated with more formulated feed.

HSB Ladder

Though GAM may persist in ponds where LMB and other predators are reproducing, their number will always be far below their potential. So they aren't going to provide >400 lbs of forage in the 2nd year and the years that follow in those cases. It is unclear just how much they provide where they are limited by predation/cover far below their carrying capacity potential. All I can tell you iis that whatever standing weight they can achieve .... the production will be a fair multiple of that.

Wow Jpsdad, thanks for taking the time to write up that much info!

The gams in our creek seem to face some pretty tough conditions, yet whenever a stressful condition subsides, they rebound very quickly. Definitely going to add them to the initial forage stocking for any new pond.

Since the preferred diets of FHM and Gams do NOT perfectly overlap, I wonder if an initial pond stocking with both species would provide a higher standing weight of available forage?

Does anybody know what is the most common limiting factor that controls the pre-predator standing weight of a new pond's initial small forage?

1.) Reproductive rate? e.g. the FHM have not had time for enough spawning cycles to "fill" the pond before the BG and LMB are introduced?

2.) Oxygen limited? e.g. the pond can fill with enough FHM numbers in the absence of predators to cause an oxygen crash and subsequent fish kill?

3.) Food limited? e.g. most new ponds have lower fertility, the zooplankton and available consumable plant material can't be that high when the pond is initially filling?

I would guess #3, but any expert commentary would be appreciated.

I have read old guidance about fertilizing ponds with cow manure, or throwing in a few bales of barley straw. However, I don't see that advice given out on Pond Boss to all of the new pond owners that are just starting their adventure. Is that type of fertilization not worth the effort? I would think that some new ponds have very low initial fertility. A little bit of help might have a significant benefit, especially for landowners that already have those types of materials on their properties?

FishingRod,

I think that a combination of minnows would be better than either alone. In particular, the FHM begin reproducing earlier and the GAM reproduce in the hot weather when FHM stop spawning. So my sense is that the combination is better.

With regard to limitations, I think you are correct about #3 as being the primary limiting factor. Reproductive rates tell us a lot about how fast the limiting standing weight can be achieved. Yes, FHM and GAM though they are very resistant to low DO can have fish kills when they are not cropped.

On the final question, I would just say that I wouldn't use manures for fertilization in my water. Of all the available organics for fertilization, I like rice bran best but whether to use organics depends on what you are trying do and the existing status of mobilized nutrients in the water. Organic fertilization produces the best bang for production of fry.

One possibly relevant observation from HSB and LMB pellet feeding: When dealing with small pellets they greatly prefer to swallow multiples. BG, even the largest, are okay slurping down a single 1/4 inch pellet, but not the big boys. Pellet groups of 3 or more floating together are much more attractive for large predators!

This behavior may carry over toward GAM and FHM, thus making the energy costs of consumption less onerous than usually assumed.

Fish growth and density is always dependent on the water's productivity. Natural productivity varies a lot. I am aware of waters with as low a productivity as 50 lbs per acre up to 2000 lbs per acre. Productivity can be enhanced by fertilization, feeding and water quality improvements.

With any species/fish there is an energetic point of no return. If the energy required to maintain basic body functions can't be sustained above what energy is expended to obtain food, then that fish is history before long.

I would not want to be a LMB trying to survive on nothing but gams and/or FH.

Thanks ewest for the important caveat.

This thread has gotten a little long, but I was referring to options to load the pond with forage in the pre-predator, early-predator stages.

LOL, the thread did take a few twists and turns. Mostly I just wanted to share the paper which demonstrated how LMB use energy. They just happened to use GAM for the source of energy but I have found if you adjust for BG energy content ... the results are consistent with generally accepted numbers for maintenance and conversion. I wasn't aware that LMB could assimilate 73%-80% of what they eat for metabolism and growth when what they eat is fish. Opened my eyes....

That said, it is pretty remarkable that one can grow 2" LMB to ~2 lbs in a year on GAM. For grow outs with young fish I see a lot of promise with them. For example, I used to think about how to grow LMB fingerling maximally in a 1 year grow out by changing up the mix of prey being careful of timing. But why make it complicated? 1 lb/acre of GAM, fertilizer, and 100 LMB/acre is all that is needed. That said, I think a nice 2 year grow out could be accomplished adding adult BG to the mix possibly in the fall (say maybe 40-60 pairs/acre in the fall).

Heck we never went here ... but what if you used dehydrated (or mostly dehydrated) fish as feed? Estimates of growth at 2% body weight is just so insane that I don't trust an adult LMB's metabolism could handle it. What percent of an adult LMB's body weight could it eat of a feed made almost entirely of dried fish? I have to wonder if growing too fast would be very harmful or possible kill it. At 1% dry weight consumption of dried fish it would be like consuming 5% of wet BG. Nothing for 4" LMB but 12"? Maybe too much?