Pond Boss Forums Thread Like Summary - Fish holding capacity

This ties into a previous post I had about a 1.3 acre pond ond overpopulated with crappie and bluegill. It now does have a few larger bass( one is 4 lbs), but I need to add more. We have been removing crappie and bluegill by angling. Several of us and our kids have worked hard at it and removed an estimated 800 BG and Crappie this spring so far. We have weighed a bucket full of these fish and estimated we have removed 200 lbs of fish. How do we know when enough is enough? I assume this weight will be replaced by something over the summer and fall? If I add 10, 12 to 15 inch bass, it should increase the bass size and the bluegill and crappie size? Or does it just get replaced by smaller fish? Or does it not have to get replaced?

My concern is we take every bluegill and crappie out that we can catch. At what point do we need to throw the slightly bigger bluegill and crappie back to get bigger bluegill and crappies? Or if only removing by angling is this not a concern because we could never catch them all?

Can we make a decent estimate of the population knowing what they weigh and using Iowa DNR guidelines for weight per acre of average farm ponds in our area? For example, can I assume if said pond's holding capacity of bluegill is 500 lbs, it will have roughly 500 lbs of 1 lb bluegill, or 2000 1/4 lb bluegills? Or if overpopulated and stunted, the weight of bluegills in the pond is actually higher and therefore hard to guess the total population?
Thanks for any advice

I don't know of any particular research documenting this for BG, but I do know of research pertaining to LMB and the yes feed trained bass tend to rely on feed. We must keep in mind, however, that BG do not need to be trained and have already developed the skills required to survive in the absence of feed. But then there are other variables. If feeding intensifies the natural bloom it will provide alternatives to fry and also reduce the visibility providing some level of cover. Whether, more or less fry are consumed by BG & BCP is a tough call and I don't know the answer. Even so, I do think it is probable that feeding will allow more YOY to survive due to the enhancement of bloom and fertility.


Just an anecdote but I have caught 2" BG on 1/2" Gams.

I would think that by the time BG reach 1" in size they are cannibalizing younger BG fry and other things bigger than typical zooplankton. Just keep in mind that millions upon millions of fry will swim up and there can be several peaks in spawning and BG can spawn more than once in a season. Feeding will help to boost zooplankton for the BG fry to feed on. A slaughter must take place and it does. Very few fry survive but this doesn't necessarily mean that BG are not able to over reproduce themselves. Buck & Thoits studied BG in monoculture and they attain individual counts into the 10s of thousands per acre without a predator like LMB. On their own, they cannot control their numbers except by mass mortality events where it may be said they were the cause of their own destruction.

A simple trick to improve your entire fishery would be to put maximum harvest pressure on the female bluegill. Take out every single one that you can. Be relentless. This way you can never harvest over 50% of the adult fish. There will be enough males left to occupy all of the key spawning grounds which means that the smaller males will continue to add weight in order to compete next year. In a pond that is over an acre, if you keep every crappie that is under 10 inches you’ll eventually establish a small population of larger fish. I’m sure catching an 11 incher every once in a while would be a treat. Two years from now would you prefer to be catching high numbers of small bass or small numbers of big bass?

The 18" LMB was probably standard weight pre-spawn.

OK. So based on these numbers and those that you posted in the other thread we have the beginnings of a fall forecast. Lets work the assumption that the weight harvested with be replaced through growth of the existing population. Truth be told, it should be greater than that and it is very likely that last fall's standing weight was greater than this spring's. Even so, there will be recruitment and so with a little luck the existing fish get the harvest gain and the recruits get the fall minus spring gain.

Lets convert the harvest to acres (where the gross acreage = 1.3)

225 lbs / 1.3 = 173 lbs per acre

60% BG = 103 lbs BG/acre

40% BC = 69 lbs BC/acre

Given you are in fertile farm country lets assume 500 lbs/acre for carrying capacity. This could be high or low but it is reasonable for an older bow in northern MO or southern IA. To be sure, the standing weight for LMB will probably sustainably max at 100 lbs/acre but the standing weight may be much smaller as a legacy of the fish kill earlier experienced. The 8" crappie are helping with the BG predation and so many of your BG are big enough to harvest(though smaller than you would like to have to harvest them). You should keep this in mind because at this point harvesting BC without increasing the LMB could remove some much needed BG predation.

So I think it is useful to attempt to gain a sense of what percentage of weight you harvest from each species. In the case of BC, I think you harvested a remarkable percentage of your existing fish. BC standing weights are typically less than 100 lbs but they can be as high as 170 lbs. I have never seen anything documenting standing weights greater than this though I suppose it is possible albeit unlikely. We will make an estimate and use this as a base line for forecast. Now we are going to be wrong but it is worthwhile anyway. The reason it is worthwhile is because the growth this fall will help us to estimate how much we were wrong and that will guide us to better numbers. I am going to assume a spring standing weight of 140 lbs BC/acre. If so, you removed half of the crappie! Well done!

Now this leaves 70 lbs of growing space and your remaining BC have the potential to double in weight. To double in weight will take them from 8" to approximately 10". Maybe a little less because they will be filling out too OR maybe a little more because the harvest will help secondary trophic organisms to be more numerous. But 10" is a good base line to look for this fall for your BC. If they exceed, then maybe the carrying capacity is less than I estimated, if they fail to achieve the 10", then maybe the carrying capacity is greater.

Now to the BG. If we assume 500 total weight/acre and that the BOW carried 50 lbs LMB and 140 lbs BC going into spring then the BG carrying capacity is 310 lbs/acre (with BC also present otherwise would be greater). So it looks like you may have harvested 1/3 of the spring standing weight of BG. Again ... Well done! Assuming your present standing weight averages 6" in length you can expect a 50% gain in individual weight and an increase to an average length of 7". What is clear is that there is much more room for you to harvest BG. And so I think you can grow the BG to an average length > than 7" (this year) if you continue harvesting through the summer. I think you could harvest an additional 100 lbs of ~ 6" most of which (weight) will be replaced anyways by Fall. Clearly, in your particular pond, the BC or more easily managed and require less harvest than the BG.

Now this takes us to Fall. Guess what? The harvest isn't over. You could harvest potentially another 90 lbs of BC still having 90 lbs to grow into impressive specimens and another 130 lbs of BG. This would take your pond into winter with 273 lbs BG, 90 lbs BC, and 65 lbs LMB(assumes 50 lbsLMB/acre) . So you would be going into winter with 329 lbs/acre in a pond that can carry 500 lbs/acre. There should be better survival and even some growth through winter under these conditions. Next year, your harvest should be easier to implement and the fish much larger than they have been.

Pond - Black Swann events are very difficult to anticipate and or plan for by definition . Buffering space is one concept that helps. If you have room in your pond for all factors you are way ahead. By buffering space I mean - Something that lessens or absorbs the shock of an impact or one that protects by intercepting or moderating adverse pressures or influences.

Absent an unknown water quality issue I have from the outset thought Tracy's event was a carrying capacity issue.

Quantifying things is doable even if it is estimated based on tools we understand like RW , RC , water quality measures , plankton densities , seine surveys , electrofishing, etc. . The most important concept to keep in mind is that we are always working behind the curve. That is, those tools give us a point of reference in time that will change rapidly in advance of our management actions (delayed effect). The real gift , the "art" part of fisheries management - is the ability to foresee/anticipate future results from current info and management actions and be able to adjust to changing (unanticipated) conditions , often in mid-stream.

Hind sight is 20/20. Yes I agree fish weight per acre was to high. But remember the bushy pond weed covered 75% of the pond. That and the weather in combination killed the fish. I should have harvested more of the hsb. In my opinion, I did not have to many lmb. Here is why. The pond never had many yoy of lmb. Using fishing, and e survey never showed any numbers of small lmb. I'm talking lmb under 14" . You could not thin or cull those lmb because you almost never caught one. I removed 7 the year of the kill. That is all I caught. And almost never saw one in the pond. Never shocked one up except that first year when we shocked 10 months after stocking. We shocked up 5 in that size range so we restocked using 1 to 1/2lb legacy lmb from Overtons. As I said earlier, the pond was never in the norm. None or little lmb reproduction or yoy lmb survival the first 3 yrs. Since the fish kill, I am seeing some yoy lmb this year.

Eric, I forgot to mention those Blk Swann (Cormants) events along with all those other fish eating birds that I delt with at the pond. Did I mention those fish eating gators?