Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Relative weight charts in Excel ? Calculations?

I think Fall after the end of growing season is a good time to cull in preparation for the following year. If average RW is not at goal, then the population would have benefitted from additional culling the prior Fall or forage supplementation. What RW a person culls
isn't very important according to energetics. With energetics, a person understands what a known population needs for forage to make growth increments. If the population is known (selected) then one can calculate what quantity of forage was consumed to grow over the past year. One shouldn't expect any more forage than that in the following year. The amount to cull depends entirely on how much one wants to grow them in the subsequent year. If you take 35% of biomass, this will be the maximum growth of the biomass in the subsequent year. Growth in the subsequent year is completely independent of what RW a person culls at. What one doesn't want to do is cull a 22" fish at 90 RW and keep a 20" fish at 110 RW when these two fish are the same age.

I'll bite. You would keep a longer fish at a lower RW vs a shorter fish at a higher RW of the same age class?

Length Weight RW Fish RW Avg

20 4.95 110.00% 4.5
22 5.6 90.32% 6.2

The thinking is that the longer fish could gain the missing weight vs the shorter fish is growing slower and won't be able to max out on weight in the long term?

At first I thought you were inviting others strike a conversation (something I think would be great) but after re-reading ... I think you wanted further comment from me to explain my case. I will oblige.

Sure, I would keep the 22" and consider taking the 20". Here are the reasons why.

1. I want the faster grower (22") to be giving its genetics to recruits. Removing the 20" LMB takes her slow growing genetics out of the equation.

2. Together, at a Northern OK location, the two LMB will consume 52.75 lbs of forage for maintenance, a similar (variation less than 3%) amount was consumed over the past 12 months. By removing the 20" LMB, this quantity of forage will be available to the 22" LMB. If it were to consume it all, the potential for weight gain would be ~3.8 lbs over the next year. At a reasonable Length Increment of say 3/4", this would be a RW of 136. This is high but achievable. There is potential for the 20" LMB to gain to the same weight but given a reasonable growth increment of say 1", this would be a RW of 177. This is very high and at the limits of known data. The probability supports that the shorter LMB probably wouldn't consume as much as the longer fish would.

3. Keep in mind that the history supports that the longer fish grew faster and has more growth potential. This is evidenced not only by the length but also the weight. Competition is limiting the larger fish where it is denied the forage ration that would allow it reach it full potential.

It does make sense, but I'd have to admit when I first looked at it I had to double check it. My initial split second thought was "why would I keep a lower RW fish over a higher performing RW fish". The answer in the breadcrumbs was length and age of both fish.
- Had both fish been the same length / age. the 90% RW is likely gonna be in the frying pan.

When I input it so I could see it in the spreadsheet...I questioned what the purpose was. Genetics, and food availability make perfect sense. Thanks for the extra explanation.

The thinking is that the longer fish could gain the missing weight vs the shorter fish is growing slower and won't be able to max out on weight in the long term?

Here's the problem with that.. If at 90%, this fish has LOST growth potential. It will never achieve the true potential of the other, shorter fish assuming it stays at or above 100% RW, even being the same age.
Maybe that's where you were headed with this but they need to stay above 100% to really have trophy potential, or even a normal growth rate.

Only relative to itself. It has probably lost some of its growth potential because it probably did not make its full potential length increment in the last 12 months.


It's already exceeded the potential of the other. It has nothing to prove about its potential for growth because it is longer and heavier. The shorter fish is remains the slow grower. It just takes less forage for it to achieve 110 RW because it is inferior.

The longer fish has more frame to gain on. It will gain in weight based on consumption. The key to its growth is consumption. Life will limit the longer fish, but to overtake it, the shorter fish of the same age will have to live longer. Chances are good, that when signs of forage limitation are showing, that neither fish will maintain RW without mortality of peers.

Snipe, think about it. If what you are saying were correct, then stunted fish couldn't resume growth. I've personally seen 9" LMB grow to 13" over a 6 month period over winter. Their RW was very poor and no telling how old they were. They were bucket stocked into pond chock full of little GSF. To be sure, they lost years of potential but they ate as much as they could over the 6 cool months and tripled in weight. To be correct about what you are saying, being at 90 RW would have had to severely impair the 22" fish from consuming excess above its maintenance or consuming as much as the 20" fish can. It already consumes more than the 20" fish does because it is heavier so there doesn't seem to be any plausible reason why the 22" fish couldn't or wouldn't eat the forage freed by removing the 20" fish.

Again, the 22" fish has nothing to prove. Its bigger and longer than the 20" fish. Its just that it is easier for a 20" fish to be RW 110 than a 22" fish to be at RW 110. It takes less forage, that is all. We want high RW because we know that fish are achieving their full potential. I would agree that 20" LMB has achieved a good proportion of its inferior potential where the 22" LMB has lost some of its superior potential.

That's over-simplified to me. Differences in forage type and size can create this, BUT, I do believe a fish has to-at some point-be X weight to achieve Y length, but if it doesn't continue to eat the most bang for the buck (FCR), the other fish will pass and out-grow it. Maybe the 22 had an easy year or 2, but it's missed out on something, it's lost weight since and growth slows way down. The 20 will more than likely pass it in the next year.
I've seen this in WAE we've tagged in fall net samples and recaptured 1-2 years later in spawning nets. The largest fish tagged are not always the largest when recaptured, in fact I'd say it's a 50/50 deal. Very hard to predict.

Scenarios like this happen EVERYWHERE, in everyone's 6 or 7 year old pond and in all lakes and reservoirs. It is a consequence of forage limitation. When there is plenty of forage to fully satiate a fish, that fish will almost always be of high relative weight ... with few exceptions. There is no way the 22" was 90 RW when it was 20". It may have had higher RW than the other LMB at 20" and indeed probably did because it was growing faster. It would have taken two years to decline to 90 RW and during that time it would have probably gained only a few ounces. Some may want to blame the fish, as you seem to, but the source of problems like this is forage limitation. There is a wall a population reaches where the population and forage production balances to a ultimate size limitation. In the example above the size limitation is between 5 and 6 lbs. We could say that the population "stunts" between 5 and 6 lbs (currently between 5 and 6 lbs, without population management, the "stunting" weight will decline with time).

Taking either fish will benefit the other. Taking the 20" fish is what I would personally do in my pond knowing them to be of the same age. For the reasons I described above. The RW of either fish will improve by taking other out. The outcome would be good either way. But one will not get the chance to test the outcomes and then choose the best. He has to make a choice and then live with the choice he made. If he doesn't take one of them out, then the table below shows what he can expect with the same forage consumption. 2023 is the current scenario ... 2024 is next year's expectations on the same limited forage consumption.



When a fish's weight gain stalls they still grow longer. RW declines as their weight stalls because they grow longer. They trade muscle and fat for bigger mouth, fins, and bones. The larger frame helps them adapt to more limited resources enabling them to survive longer eating fewer but larger prey. When forage is limited, RW will always favor fish that are shorter than the longest fish. As proof of this I offer the Texas Top 50 where length explains ~90% of the variation of RW.

Forage limited is a good term, but also it's the size of the forage that limits the growth. Calories gained vs calories expended.

Another aspect of LMB ponds is that if the bass don't have places to loaf and ambush their prey, even with a good forage base in the pond, they will be expending more calories by swimming constantly and also expending more calories by not being as successful at catching fish as they would be if they were ambushing them.

I compare those LMB in ponds without the correct cover (habitat) to marathon runners. While they can consume plenty of calories to gain weight, because of their caloric expenditure they cannot add the weight like "couch potato" LMB in ponds with the same amount of available calories but with proper cover (habitat).

jpsdad,

I find your next to last chart, VERY interesting! (Texas Top 50 - RW v Length)

I read most of the RW posts in the forum to learn how people's pond management and feeding programs are helping their fish. I just assumed RW was a "pure" data point about how effective the pond feeding program is working, or the forage population, or the stress, etc.

That chart certainly seems to indicate that fish have some inherent morphological differences. Some fish grow longer with adequate food supply, some are stouter and fatter.

It sure would be nice to know on that chart, which fish were northern LMB, versus Floridas, versus F1. I suppose there is a chance that the type of LMB is causing the dispersion?

Glad that it interested you FishingRod. I looked at all of the relationships I could plot in the Texas Top 50 data. Most displayed R^2 less than 0.01 and none displayed this level of correlation. It was not expected. I just couldn't rest until I resolved why. What I found is this. The function the distribution regresses to is the RW corresponding to the average weight of the distribution (16.2 LBS). This is the weight where growth of Texas LMB stall. Keep in mind, however, that Lake Fork (responsible for most of the Top 50) hasn't produced a fish > than that average weight since 1996. So this wall of 16.2 pounds is the past for Lake Fork. The number is lower now due to population differences and such. Its wall is lower than that now.

FishingRod, after seeing how tight the relationship was and how RW favored shorter fish ... the first thing I wondered was this. "Could selecting fish on the basis of high RW and removing fish on the basis of low RW select for slow growing offspring?" Here is the answer I arrived at. Yes, but this would be especially prevalent when the population biomass is at or near carrying capacity. IOWs the risks are greater when populations are experiencing forage limitation which would impact the those at the very top of the food chain the most (larger fish that were also the fastest growing).

It is possible to keep fish growing maximally and maintain high RW. But for this to occur, forage availability cannot limit their growth or prevent them from reaching satiation. Under this condition, I do not know if fast growers would have lower or greater RW than slower growers. It is conceivable, that fast growers grow faster because they are more apt to consume when their RW is high. There could be a tendency inherent to the individual genetics that governs when a fish is satiated or is inclined to stop/slow consumption even when prey is abundant. One fish may stop eating when its RW reaches 140, while another 160, while another 180. I don't know but if a fish begins to consume less when its RW reaches a threshold like 120, then you will never get that fish to a RW of 160. Could this be difference between slow growers and fast growers? I don't know ... but it would be an interesting program of research especially if that "consuming at high RW" were a genetic trait that could be selected for. Even so, fish are still limited by their environment. A fish with such promising genetics can only do as well as its consumption of forage will allow. Deprive her of food? She isn't much different than any other fish unless she is a very determined competitor who can take more than her share.

Oh I almost forgot about your last question. Before the introduction of Florida LMB, Texas produced fish <14 lbs. Florida genes have had a positive impact on ultimate weights. I suspect all of the Texas Top 50 possessed some level of Florida genes.

Most all of our KS bass tested have "some" FLA alleles of some measure. They were found in our Meade hatchery years ago and all fish were (Brood stock) removed and destroyed.

Did some idiot bucket stock a hatchery pond?

Or did the State get some brood stock from Texas (for example) many years ago, before they thought there were Floridas in that line of LMB?

The KS state record fish was recorded to be 28.5" long. A substantial fish and I wonder if it had Florida genes from a private stocking of F1s. It must have been pretty dog gone old. Was only ~81 RW and so one has to wonder how heavy it may have been in its prime. The weight was recorded to be 11.8 lb .

Here is a link an image of the KS state record. The condition doesn't appear poor to me. Caught on 05/03/2008 so spawned out?


https://bloximages.chicago2.vip.tow...509-0bd195873aa1/53cd9a00769c8.image.jpg

I'd be happy if I saw that big girl swimming in the pond.