Pond Boss Forums INTRO Questions & Observations Carrying capacity

For the sake of open discussion, I'd like to talk about carrying capacity and what it means.
We know there are individual items that can increase carrying capacity to a point, BUT....
What happens when (I'm using a customer's pond as an example, or exhibit A) the owner has 3-4 species of fish, fairly balanced in most ways, then because of reasons I've yet to understand, gains access to about 120lbs of full-on adult bass, adds them to his pond and a year later, starts finding a big adult bass about every 3-4 days-dead. No other species visible as morts-only the adult bass, but they are good in body condition, no wounds, fungus or any visible ques.
This begs the question how and at what point does carrying capacity inflict mortality without affecting body condition?
Last summer, his bass were on nests, but only 1 nest noted of 23 produced visible fry. 22 male bass remained on nests for nearly 2 weeks before slowly abandoning the areas. I got on top of some of these and shot some video trying to get him some good footage.
Should this have been a sign of the adults not effectively reproducing by knowing it was over-crowded??? Is that possible?
I'd like to hear some thoughts on this.

Are those adult LMB the biggest fish in the pond? If so, could a low DO event have happened that only affected the largest fish in the pond? Unless something drastically changes, a low DO event usually won't be just one night.........


What size were they when they were introduced to the pond? What size are they when they are dying? Any idea what age the fish are?

Love the question Snipe. FWIW, I do think that exceeding the carrying capacity by stocking additional adult LMB will cause mortality. The standing weight of LMB will rebalance to the weight that the production of consumed foods can support. This could kill fish ... especially the larger ones. I guess, what I don't understand is why the client's fish died when in good body condition. Esshup's suggestion of water quality parameters seems to be a very good place to start.

Interesting about the LMB nests. So what did you think happened? You mentioned 23 separate nests. So there is preparation of the nest, followed by seduction of females, and if eggs are laid, he will try to protect the eggs and fry for a short period beyond free swimming. Did they all get eggs? or was this possibly the missing link.

Scott:
morts are all about 16-18" fish and NOT the biggest fish.
I should have taken otolith out of everything he's found but only did 1, the fish appears to be 7 yrs old as best I can tell with my fisher-price microscope.
Pond is aerated-efficiently, 4am to 7pm, various vegetation types are coming on, good macrophytes, should be good O2 production. 5:30am O2 check last week showed 6.3ppm at 3'. WT 59*. Water clarity is a good 3' . Several species present, including my YP, BG, a few RES and a few 3-4lb SMB. The only other fish we've found was a small 2.5" BG. Full of GSH, never see but an occasional wounded fish from GBH.
I have pretty much kept a tight rein on this pond as it's only 20 miles from me. The water tests that I can accurately check are good.. simple pH-7.8, "smell" of water is that of a very healthy pond-you guys know that smell if you spend a lot of time around ponds, some have no smell and are less productive.
Water looks super, but only morts are LMB in the above range.
My thoughts are fish that were not growing well were introduced, mother nature said no room for more, Bass tried to spawn but eggs in most nests, 3 did not have eggs but males stayed a very extended amount of time.
One thing he did change last year besides addition of the adult bass, was about 75-80 2lb trout.

jpsdad, I can't find an obvious issue with water. Cycle of pond is exactly how it's been for 9 years.
Another thing I should add is he rarely sees LMB production of any number. He pulls all 6-10" LMB but it's been very low numbers and has never purposely harvested a single large adult LMB.
In trapping, we see a few BG of varying sizes, a few YP, occasionally a small LMB or 3, but never have seen much for reproduction of LMB. BG seems to be very different every year
This is a 3/4 ac pond.
I'm starting to wonder if these as less than perfect bass that have reached end-of-life at a specific age.

Exceeding carrying capacity is like running an engine too hard. It usually breaks the whole thing - major fish kill. I don't think carrying capacity issues would kill only one size fish of one species. Here is the seminal carrying capacity thread. Most ponds in the south reach unaugmented carrying capacity in 18 to 24 mths post original stocking. After that you are managing population dynamics - year size classes and morts.

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92440#Post92440

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=19169

ewest, I read through several of the threads prior to posing the question of "why LMB in this size only and only 1 every couple of days".
Maybe my question-to simplify-is why is this occurring with exact size class of fish?
I know that's a loaded question and probably not any simple answer, but the dynamics of not removing any big bass-ever-has left me questioning what the limit is, and what happens when reached. I expected to see declining body condition-that isn't the case.

Take that back, he called and said found 3 today, the most in 1 day, all 15-18".

Snipe, if those fish are averaging 2.5 lbs, how many should there be in a 3/4 acre pond? He stocked 100 lbs of adults in addition to what it already supported so what are your thoughts on what the carry should be for that 3/4 acre pond? I could understand more than 60 lbs if LMB were taking feed and/or forage is supplemented.

So the condition isn't poor. Is there any chance there is disease that doesn't have external symptoms that are easily identified? Truly don't understand what could be causing the mortality. Any chance feed was contaminated in the feeders where mold toxins may have played a role?

Kenny, I think you hit the nail on the head. Older fish, not the best growers, and they are just aging out. Just because a bass usually lives 10-15 years, doesn't mean they all will. Under performers that have been stressed most of their life will die sooner than fish that haven't been stressed their whole life. That's just my opinion though.

Pond is fished quite heavily, bass are recaught even on the same day sometimes on minnows (GSH).
There are some diseases that could be affecting them that only show up in certain species and there may be no external indication-which is what we seem to have and with temps warming, the timing is such the bacteria could be "Popping" and causing a toxic, spring kill.
Feed is first-run Endurance, some of the very first bags, no old feed.
I did some reading on this and am somewhat concerned on the addition of farm raised trout, this could be playing a role as a stresser as well, not sure, but sounds like it could be possible.
jpsdad, based on sampling, the estimate on total bass weight last fall would be well over 250lbs for the total 3/4 ac.
As of tonight, I'm estimating 49lbs of bass morts in roughly 16 days or so, yet catch rates of this size bass and larger are still very decent. It sounds very conflicting but it's happening. Again, in (I think) 9 years, these morts are the only bass above 14" that have been removed from day 1.

I agree with Eric on his comparison of running an engine at high RPM. Even if water quality isn't the present cause of mortality. It's going to be at some point unless he can make substantial water changes and monitor the water quality on multiple parameters. Ammonia is one in particular he should be concerned about. Though it probably isn't the cause of recent mortality. We haven't mentioned this yet, but the water quality may provide enough additional stress to shorten lifespans. Where in clearer, cleaner water they might have lived longer (here assuming it was old age that killed them). For LMB less than 8 years of age and exceeding 12", perhaps 10% is a reasonable expectation of annual mortality (in Texas). If he is carrying around 120 per acre, 10% mortality (12) would be normal.

Snipe, there is a lot of fish in that 3/4 acre. 331 lbs/acre of LMB. If feeding on BG that are produced in pond they need 1436 lbs of consumed BG every year for maintenance. With GSH they need 1228 lbs every year. Blended it's something in between those two weights. Just counting the LMB and Trout ... around 531 lbs/acre. Are there BG? Generally, LMB (if not eating feed directly), will balance with BG between 12% to 18% of the BG+LMB standing weight. So if BG are present, maybe over a ton per acre for the total standing weight? What do you think Snipe, what are your thoughts on the total standing weight? Is a ton per acre of standing weight possible in that pond?

Heavily stressed fish don't last long. For northern LMB that have been living under stressed conditions and caught several times and are 6+ time is running out.

Does anyone know the age of the added adult bass? Just thinking

One common admonition on handling bass is that we are damaging their protective slime coating when held in dry hands.

If frequently handled bass caught a fatal infection, would that manifest as obvious lesions or damage on their exterior, or is there a chance that an external pathogen reached their bloodstream and did interior injury?

(I have no clue as to the answer, just trying to learn more about how handling the fish causes stress, and/or injury or death.)

Kenny - you say owner - "gains access to about 120lbs of full-on adult bass, adds them to his pond and a year later starts seeing dead LMB"
Are those dying LMB the sizes of LMB that were added?
So 120 lbs of adult LMB were added on top of an existing LMB population that had been historically unharvested or rarely harvested? Correct? Do the newly added LMB eat pellets?
They lived a full year and now in spring of 2025 are gradually dying in decent body condition?
Do any have eggs for the upcoming 2025 spawn?.

Lusk usually says adding adult fish to another pond is sometimes not a good thing. Adding a higher quantity of adults may make a not so good thing worse especially when the pond was at carrying capacity prior to when the new adults were added? A New environment and too many new stressors for the immigrants who now have to compete with resident established, adapted individuals in a capacity pond that did not endure harvest and transportation stressors?

You guys have all changed focus to where I was pointing in a "not so obvious" manner.
Although I don't know the answer, I suspect several problems that were induced.
1., Adding adult bass is not good. (I agree with Lusk and advise the same)
2., adding adults in an existing body with healthy fish present could be an immediate stressor for all parties.
3., The amount of fishing pressure has been extremely heavy-additional stress.
4., the 1 fish I pulled otolith from (if I am correct in my observation of cut sample) was 7 years old, possibly near life's end.
5. ALL morts so far have been female-all had eggs, but I have been unable to determine if these fish were part of the 120lbs of additional biomass or not.
6., Fishinrod, don't cut yourself short, research has shown internal issues can at times cause mortality without external evidence and "usually" flares up in early spring from what I can find..
7., As smart as I "think" I am, I only can speculate there is a limit certain species of crowding will tolerate.
8., I am somewhat concerned about the high number of extremely aggressive trout added last fall and may be playing a part.
At this point, I don't think I see a clear answer, but I am sometimes blinded by non traditional management (adding extra adult bass) as I was not asked if this was advisable because My gut tells me that's not been a real good thing in a fairly good pond.
I'm not a chemist, but I can say the chemical properties I've checked are not out of the normal range. Nitrates are about 22, Nitrites and ammonia appear to be nearly unreadable.
The smartest thing I've done so far was have him pull the 3 morts last night and freeze in individual bags in a floor freezer, as I will be sending these to WADDL for testing.
I hate to say I don't know, but in this case, "I don't know" because I can't prove anything yet.
The ideas and discussing helps me to look at different view points and I'm appreciative of the input.
My initial thought was overcrowding-overnight-with a possible tie into the trout. My thought was induced problem by introducing adults combined with heavy pressure, then the thought -or question-came to mind of just how many lbs of 1 species would survive without evidence of negative impact.
When he told me about adding the fish, I fully expected to start seeing reduced body condition, but that didn't occur as I thought it would.
This will be an expensive test (monetarily for me) and a loss of time having a decent pond for him.

I was wondering whether the morts were female or male. The lengths are consistent with managing for higher population and slow/moderate growth (depending on perspective, to a person that wants trophies, that is slow, to a person who wants balance, that is just right). Females growing by ad libitum consumption could make the average weights of the morts in just a couple of years. Sometime ago I was trying to understand how RW plays into all of this. Fish in the range of 95 and 110 appeared consistent with fish growing at around 25-30% of maximum potential. Those fish were growing (average for their age) at 27% of potential in a Goodland, KS climate. They very well could have marked better growth than that earlier in life stalling over the past few years. FWIW, RW is highly variable and can swing all over the place for fish of all the varying potential of average annual growth. Don't use a RW of 100 to conclude a fish is growing by 25% of its potential.

Just a theory ... but here goes with some background. I think the marking of length increment is important for survival. In the Texas 17 year study that Eric introduced me to, the survivors almost all recorded length increment. The exceptions were explained by damage to fins cause by spawning activities. Morts were not part of the growth data, but this suggests that survivors do have length increments. Length increments even occurred in the rare years that there were declines in average weights. In years where there were declines in average weights, these were high mortality years. So growth may in some way be important to an individual's fish prospects of survival. In the Texas study, the fast growers demonstrated they had a higher rate mortality. But as they grew, the separation of the weights of fast and slow grower declined. What this means is that the rate of growth of slow growers eventually overtakes the rate of growth of fast growers. Fast growers rate of growth stalled sooner than the slow growers.

Fast growers have really good initial growth but eventually divide between the fast growers and the slow growers becomes too broad to benefit equally from forage production. For two LMB to grow at the same percentage gain, they need to consume similar proportions of their body weight. Because the fast grower weighs more, the consumption required is proportional to the ratio of the weight of the fast grower to the slow grower. Each only has one mouth and each are afforded a similar number of opportunities for whatever prey is present. But the slow grower has an advantage. Its optimum sized prey is smaller than the fast grower and so unless the prey starts at a size that is more optimum for the larger fish ... the smaller fish always maintains a competitive advantage (here I am talking adult LMB > 3 yrs age ... not fingerling or adolescents). A smaller LMB can grow at a density of prey that the larger LMB cannot. Keep in mind that as a cohort of prey grow, their population density declines. So, as an LMB grows larger, the availability of consumable prey eventually falls below the density required to maintain its weight.

I think this is in part why fast growers die younger. They stop growing earlier than the slow growers do. Perhaps, something internal accelerates end of life when growth stops. To be sure, such fish forage more frequently without success and undergo more stress than fish that are growing. Don't know for sure but growth seems to be an important contributor to the rate of survival.

jpsdad - for clarity of understanding for all readers please define and usage of - 'length increment' as used in your post/s.
".... the marking of length increment is important for survival."

A fish should grow longer each year, even if it doesn't gain weight. A length increment is an increase in length over the course of year. If a fish is not consuming enough to grow a little longer, it is probably losing weight over the course of a year and is at higher risk of mortality. Like I said, just a theory, but maybe life is over for LMB when the prospects are no longer looking good for growth. Time to hand off the baton so to speak.

Cody Note - thanks for the explanation of length increment and enhanced information. Helpful to all fish growers.