Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Amount of maintenance food req'd.

I know that the numbers will vary from region to region (N vs. S).

It's been discussed that 10# of forage food is needed to put 1# on a LMB. We also know that for a LMB to get to "X" length, it has to weigh "X" pounds.

But, how much food per year would be required to keep a fish at a certain weight? Say a 21" LMB that weighs right at 5# for a WR of right around 100 would require "X" amount of food per year just to stay at 21" and 5#.

Is it the same for different fish species? I'm assuming that CC and RBT convert a larger % of food to weight just because they are the commomly raised food fish.

I don't remember this being discussed in the past year or so.

I've also wondered that. I was told by a TAMU Prof last year that a BG had to only eat a couple of times per year to sustain life.

That may be true Dave, but sustaining life and keeping the WR the same are 2 different things.

Nice topic I too would like to know since I am now starting out and trying to do it the right way.

Agreed Scott

Numerous variables with an answer for this topic.
1. Temperature of water - digestion rate - seasonal variation.
2. I would be very suprised if all fish digest at the same efficiency. Fish physiology. Thus species of fish may make a difference.
3. Food type. Definately some foods are more nutritious or contain more energy than others. Example crayfish do not contain as much food / energy value as say shad.
4. Fish's activity level. IMO an actively swimming fish such as HSB would consume more calories than say a sedentary catfish.
5. Maturity level. I would assume that an immature fish may require a different basal amount of nutrition compared to fish that is preparing for reproducion.
6. Sex of mature fish. Females preparing for the spawn would require more nutrition compared to males.

I have read that fish do not have to eat during winter (temp 39-40F) and can absorb enough vitamins and minerals from the water to sustain life. Although some weight loss may occur during the winter if the fish does not actually 'eat'. Some fish are definately more active in cool/cold water than others. But this may be compensated during very warm water when cool/cold water species are relatively inactive. Again this inter-relates to items above.

Good thoughts. My suggestion is keep it in very general terms as per Bill's comments. The study of bioenergetics (which is what you are asking about - the field of biochemistry that concerns energy flow through living systems ) includes all life functions and environmental considerations. It’s through that process of accounting for each life function and variable that a # is reached. Trust me the equations are unbelievably complicated and still being changed. More later.

See this http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=126776&page=1

The problem with this question is that we don't know enough about large-mouth bass or bluegill nutrition. We would have to put them in a feedlot setting like we do with cattle to figure it out.

It is a very interesting question, but no one cares enough to spend money on figuring it out because they aren't going to make any money off any discoveries or developments.


We don't even know how largemouth bass go about energy partitioning or how they use the nutrients that they acquire. Sure, we know the basics of fish physiology, and can extrapolate what we know about trout and catfish, but we would still be WAY off the mark (not even close, but growing fish well below their potential is better than not growing them at all!).

Even in humans, which we know a great deal about (We actually know more about livestock though, interesting huh?) we haven't figured out how much Vitamin C, or vitamin D, or the amount of B-complex vitamins are actually required for growth.

You might argue that we do, because the government has listed numbers for the amount of vitamin C per day; however, these numbers were come up with in the 70's / 80's before they figured out the OTHER roles these vitamins play in the body (such as the formation of heme groups, clotting factors, and as coenzymes in bio-synthetic reactions). New recommended daily doses have yet to be established for humans... If we can't even figure out what we are supposed to eat, it makes me wonder how good of a job we are doing with other species.

So, to echo what Bill Cody has said.

1) We need to first understand large mouth bass physiology. The history of aquaculture in the united states kind of baffles me. For some odd reason (driven by profit motive) we have always tried to culture fish that we know next to nothing about. To me it would make sense to figure out how they work, then take a shot at mass production in an efficient manner. We seem to do everything backwards.

2) Food type... Boy is this important. This really goes hand in hand with physiology... We first have to establish what amino acids are actually essential (those that are essential in the diet vs those that can be derived from other precursors), then we have to figure out what combinations of feed are going to be the most effective.

This goes beyond just % protein, % carbohydrates % fat etc. You have to match the TYPE of protein (amino acid composition and nutrient availability) to the rates that specific types of carbohydrates will give up their organic acid skeletons, in addition to understanding how lipid transport takes place, and the efficiency of the animals metabolism in general (in respect to what environmental conditions or stressors such as starvation, or post absorptive states will turn on which metabolic pathways like gluconeogeogensis, glycolysis, krebs, de nova fatty acid synthesis, etc).

Even then, we will have to figure out exactly what vitamins are required by each fish species. Vitamins are NOT the same for all species. For example, Vitamin C is a vitamin for people, guinea pigs, and gorillas, but is NOT a vitamin for for the majority of other mammals... The other mammals can just synthesize it from other precursors. But even so, you have to figure out what that precursor is, how it is made, and make sure the animal gets enough of it.

Oftentimes if you are missing just ONE component, then you can't make anything with it (let alone keep yourself at maintenance or make allocations for growth)... Lets say you bought a square table that had a top, with three legs. If you don't have the fourth leg, the table is pretty useless and can't be completed / used.




I don't think they convert a larger % of their food to weight in reality. It is just that we know more about their physiology (people chose to study them because they are really really easy to raise, and they saw the potential for profit, so scientists picked them to study the most), so we feed foods that maximize their potential for putting on that weight. We could do the same thing for bass.

They just haven't proved as easy to figure out (or in the big wigs opinion, as easy to raise, which means less profit), but with transgenics that could change pretty quickly if we insert genes to tweak their physiology. Sometimes it is easier to change the animal than go through the trouble to figure out where you screwed up with the feed (sad, but true).


I'm not sure where I was going with this.

I'm all for the KISS system. I was thinking along the lines of "A LMB needs 10# of food to gain 1#"

A LMB needs __# of food to maintain their weight.

Lots of variables as was stated, along with the size of the fish.

Given the 10 to 1 ratio, a 1 ac pond that has 50# of LMB would need 500# of food for them to all gain 1# in a year, and that 500# would be the carrying capacity of the pond, correct? I know that's really, really simplifying things. I realize (believe) that example is using what most people would view as a static carrying capacity and not a dynamic carrying capacity.

I like the KISS system as well.

I really just haven't a clue what they would need to keep their same weight.

Does anyone know at what point a fish stops growing? To figure it out we would just need a few mature bass that aren't growing anymore (and are around the same weight), and feed them varying amounts of the same food, and weigh them periodically.

I assume that if we were to see how much food we need to maintain a bass' body weight, then we would need a fully mature bass, otherwise keeping it at maintenance would just be stunting its growth.

It might just be best to keep with the 10:1 ratio. Better to overfeed than to underfeed.

Guys there is info on some of this. For example look at PB mag for articles in the current and next issues on transgenics and small population genetics.

Nutrition plays a big part but so do other factors. See the thread I linked above. IIRC Purina took several top notch LMB foods ( RT and Shad) and did base nutrition level analysis (ground them up and did a basic chemical level analysis). With that info they matched the results to make LMB pellets.

Dang! If I could do that, I'd be back to my fighting weight in no time flat!

He probably meant twice a week. BG have small mouths and stomachs so they eat a little often if possible.

I am not too sure what my BG will eat on through the winter but the few bass that are in there will have as much as they can take with all the Gams, BG, GSF, that I have seen.

Not sure when the last spawn was but I have a ton of fish that are only an inch or so long.

Nope Eric, I asked for clarification. I questioned but don't have a clue regarding the real story. I know it has something, or a lot, to do with digestion and absorption during different temps.

During cold water (< 50 F ) BG will not need to much to eat as their metabolism is slow. Not unusual for BG sampled in winter to have empty stomachs. That does not mean that they are at stasis as they may be losing weight. I can find the metabolism/feeding info on BG. IIRC it is most efficient in the high 70s F.

esshup - give us a water temperature & a species with average size and someone can come up with a reasonable guess (WAG). Water temp can be a range of 10F degrees, i.e. 60-70F or 39-50F.

Additional comment, esshup says:

If we had a LMB with a Wr of 100 it would have enough body fat to be growing. A fish that is not growing and just maintaining body will have a significantly lower Wr than 100. I am not sure what that Wr value would be. Any experts out there that have a good idea of what the Wr of a LMB would be if the fish is just maintaining its weight???.

Unfortunately, I can't. A question was asked a couple of posts down and by my thinking, the pond can't support the number of LMB in the pond. He wants to manage the pond for large LMB. The pond is 1/2 ac. That got me thinking about dynamic carrying capacity, etc. That pond is located in Central Pa.

Here's what was asked: As some of you know in spring of 2009 I drained and mucked out one of my ponds located in central PA. Stocked it with 20lbs of FHM and about 400 BG 2-6inch averege few 8+. In Spring 2010 I had a thick forage base and alot of pond weed grew in quick. Trust me the FHM did not mind cause you can walk on them now. Summer this year I added about 40 6-12 LMB about a 12 14-20inch LMB and about 6 from 21-26inches and 5 grass carp 12 inches.

I got to thinking that if 10# of forage puts 1# on a LMB, then with (averaging the weights if the fish had a WR of 100) 103# of LMB in the above pond, how much forage had to be in the pond just to keep the LMB at the same weight, let alone put weight on the LMB.

Interesting discussion, fellas.
Almost everything I'm about to say is anecdotal...things I've learning by doing.
I believe it takes ten pounds of forage fish for a bass to gain one pound. That ten pounds of forage is eight pounds of water...two pounds of nutrition. Energy is spent digesting all the above.
Dry weight, most fish convert something to the tune of 1.25 to 2 pounds of food per pound of gain.
Fish with small mouths need to eat more often, as a rule, to maintain and grow.
The lower a fish sits on the food chain, the more it must eat to maintain and grow. For example, carp must eat lots of food...mostly because that food isn't nutritionally complete. A predator, on the other hand, is efficient with digestion, even if it isn't efficient with energy conversion to hunt and capture its food.
Fish are not unlike other multiple offspring creatures. There are fast growers, average, slow, slower. There are aggressive, passive, dominant, sneaky fish. There's a wide variety of behaviors from within the same sibling groups, not to mention the assumed genetic diversity.
So, how much does it take for a fish to maintain?
One of the assumptions in fisheries management is that a fish can, if the food supply is there, eat 3% of its body weight per day, when the temperatures are ideal.
I've watched that happen with largemouth bass on feed, bluegill, catfish and trout. That's pretty much the truth.
My theory is this...if it takes two pounds of dry weight mass for a given fish to gain a pound, the assumption is that two pounds of feed becomes a pound of fish and a pound of waste. I contend that if anyone had the inkling (I don't) to figure out the dry weight of fish poop, we could assume a value of what it took for that fish to maintain. For example, if a fish eats two pounds of its food and gives up half a pound of waste, that could simply mean it took half a pound of food to maintain...as the fish gained one pound.

Here's the bottom line...no one really knows.

From a practical standpoint, I'll judge from relative weights as whether or not a fish population, as a whole, is gaining or not.

When I consistently see fish of relative weights 90-95, I assume those fish are maintaining. When I see that scenario over the course of several months, I make a change in management choices. That's when we'll either set a slot limit and start harvesting fish or we'll figure out ways to beef up the food chain, either by stocking something to fill an empty niche or feed existing forage fish with fish food or a fertilizing program. Or, we'll do both.

Ironically, even when we have the "perfect" food chain, not all fish grow. Some maintain, some thrive and some decline.

That's the point when our management strategy gets eventful.

"how much forage had to be in the pond just to keep the LMB at the same weight, let alone put weight on the LMB."

Can't do that jump from how much "needed to eat" to "how much was in the pond". To many unknowns like capture rate and effort to catch.