Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Bream Size Distribution in Healthy Pond

Can anyone direct me to a thread or article on the size distribution of bream in a healthy pond? What % should be small, medium, & large. I am not interested in the monster bream pond but the balanced BG/LMB pond. I have read about proper size distribution of LMB.

Thanks for the help!

This is a very good question and the answer has many variables that will contribute to "balanced" or "normal" population for percentages of bluegill sizes present in a healthy BG-LMB pond. Since there can be many variables that contribute to the population structure of BG in a pond I am not sure there are any standard percentages - "It all depends". I am pretty sure there has not been any discussion thread on the PBoss Forum for this topic. I create an annual PBoss magazine contents and index for the articles. ATTENTION PB MAGAZINE EDITOR. There has never been an article written about this topic. Maybe because no two ponds or lakes are alike.
I think there is a good published study titled "Bluegill recruitment growth, population size structure and associated factors in Minnesota Lakes. NAJFM 25:171-179. I do not have access to this journal. I will check in with our Science and Cutting Edge PBoss writer ewest to look it up and report what he can find on this question.

I will provide my opinion of an answer as a best guess. First I will define sizes for the categories of small 1"-3", medium3.1"-5.9" and large 6"-9". Plus I will add extra large 9.1"-10" to the size groupings.
small 1.0" to 3.0" = 70%
medium 3.1" to 5.9" = 20%
large 6.0 " to 8.0" = 9%
X-large 8.1" to 10.0" =1%

Bill, I’m supposed to see the PB Magazine Editor today. I’ll show him this thread. Sounds like a good topic for the PB magazine.

BTW, I don’t have a good answer. I expect its another “It all depends.”,

I think this is a really great estimate. I haven't read any papers on this question in particular in the literature but Swingle's survey guidelines on balance are related. One thing I would mention is that the population numbers are very dynamic for the first two length categories and these numbers fluctuate considerably through time. The first two fall within consumable prey, the third is the core brood population, while the 4th are exceptional BG. For a total population of 6000 per acre ... this equates to 323 lbs BG/acre.

Below I hypothetically balance an LMB population with this BG population structure consistent with Anderson's population recommendations for LMB and Swingle's optimum range of consumable prey (in relation to LMB Biomass).



In the example above, LMB comprise 14% of the total biomass. I have seen this number recur as an average % of biomass in a few papers. The ratio of BG biomass to LMB biomass is ~ 7. Swingle considered 3.6 optimum but I will mention that he was very much focused on getting good growth from the BG. The reality is that populations and biomass ratios can vary pretty widely and still meet Swingle definition of balanced. Which is that a high proportion of the standing weight of both LMB and BG is of harvestable size. The example above fits Swingles definition of balanced (60%-85%) of harvestable size ... falling just below the middle of that range at 69%.

Swingle recommended that the Y/C biomass ratio range between 1 and 3. Y/C is short for Consumable Prey(Young) biomass over Carnivore biomass (consumable prey biomass / carnivore biomass). So the weight of consumable prey should exceed the weight of the LMB but be no more than 3 times the weight of the LMB in order for the BG:LMB to be balanced. In the example the ratio is right in the middle of the range at 1.9 to 1.

So here are my questions as I seek to understand population management.

1. For the first two tiers, the LMB are controlling the population recruited to >6" in length. After they achieve 6" the LMB can no longer control the population of these larger classes of BG. So what set of rules of management/harvest would ensure that >6" fish do not accumulate to excess to allow growth into the 8"-10" ranges?

2. For the LMB, what set of harvest rules would maintain the population structure recommended by Anderson? What is the best way to understand how many LMB are there? This to be sure that LMB are neither under-represented or over-represented in each respective size class.

While on the BG topic, if you put 100 fingerling 2” LMB in a pond along with 500 2” CNB, how long does it take before the LMB, grow enough to consume the CNB? I assume they will both grow at about the same rate for a while giving the CNB a chance to spawn ?

The LMB will never be big enough to consume any of the 500 2" CNBG (that were originally stocked). Cody note - Assuming adequate foods both would be growing "normally", thus those 500 CNBG will always be too big for those LMB that were stocked with the 500 CNBG to eat.

Cody: esshup had a good answer.

Thanks esshup!

I would have guessed that at some point the LMB would eventually gain a sufficient size advantage to eat the original BG stock.

Your post is a great example of the importance of getting the forage population established prior to the predator population!

About the only way the 2" CNBG would be eaten by some of the 100 fingerling LMB would be if the CNBG remained somewhat stunted due to lack of food and the fingerling LMB were able to utilize other types of foods not edible by the CNBG. In this case the LMB after several months were able to grow rapidly to the 7"-8" size group. Then these 7"-8" bass could eat some of the smaller slow growing individuals of 2" CNBG original stockers. As is often the case when a pond owner buys a certain size of fish there will be some smaller ones and larger ones in with the lot of the fish that was purchased. Example - when you buy 2" BG the measured sizes can often range from 1.5" to 3". Theoretically a 1.5" BG could be eaten by a 5" bass.

This topic of percentages of the BG sizes in a pond is interesting in regards to how many BG this would amount to for the carrying capacity of a pond.

Carrying capacity is usually determined by fertility of the water in terms of the amount of food produced within the entire pond system known as the food pyramid, food web, or food chain. For an infertile pond with low alkalinity and clear water the BG biomass in lbs/ac could be low as in 43-88 lbs/ac, medium of 100 -230 lbs/ac or high for a ‘reasonably’ fertile “backyard” pond that could have 270-660 lbs/ac.

The number of BG that would compose the percentage of BG in each size category would have a lot to do with the number, size and specie of the predators present to eat representatives of each BG (forage) size group. Also having a measurable influence on the BG numbers present would be the amount of harvest and natural mortality. Predation, mortality and harvest. If I understand jpsdad correctly, he has aptly pointed out from his review of published literature, that growth and carrying capacity does not significantly increase until the fish numbers are reduced that are causing or creating the carrying capacity (system fullness). Reduced numbers are from things such as predation or various forms of mortality. Then there is more room or space for fish growth to occur.

The fertile pond category does not necessarily have to be nutrient rich due to chemical fertilizer added directly to the water. The BG(fish) pounds could be grown to higher capacity using fish food pellets as now used by many pond owners. Using fish pellets to grow fish, the total pounds grown as carrying capacity can be very high or dangerously high and in the range of 1000 -2000 lbs per acre that are often achieved by the commercial farms that grow fish for the food market. These are places that produce very carrying capacities of high pounds of fish, as these places constantly live on the brink of fish kills due to low water quality due mainly to too much fish manure. These high fish pounds per acre require special types of artificial aeration and very close constant attention to water quality and some luck to reduce but not prevent fish kills due to conditions of too much “unhappy water”.

"While on the BG topic, if you put 100 fingerling 2” LMB in a pond along with 500 2” CNB, how long does it take before the LMB, grow enough to consume the CNB?"


Probably not. Given the question, the parameters and not reading anything else into it here's my reasoning.

2" BG and 2" LMB. The LMB would have to (basically) at that size be limited to zooplankton and other invertebrates. Same as the BG. Since the LMB wouldn't have a huge food supply (because the BG would be competing for the same food) the LMB wouldn't be fast growing. Sure, some might be able to eat their roommates (other LMB) but there wouldn't be any other fish for them to eat that they could fit in their mouths.

Now not knowing what the other food sources and quantity are in the pond, NOR the time of the year that the fish were stocked, one could assume that the CNBG wouldn't pull off a spawn until the following year. The LMB wouldn't be able to pull off a spawn until year 3 because a 2" LMB had to be hatched that Spring, so that means stocking in late June or July. To be 2" the CNBG might have been hatched that spring or they are runts from the previous year.

If the CNBG were to grow to 6" by year 2 in the pond, the LMB wouldn't be big enough to eat them. Once they pulled off a spawn, then the LMB could eat the offspring, but so would the CNBG be eating their offspring as well. So while the LMB would be growing at a faster rate in year two, so would the CNBG because of the YOY in the pond and having a larger mouth means that they can eat a larger variety of food.

Remember a LMB has to be roughly at least 66% to 75% longer than the CNBG to be able to eat them, and the way the OP phrased the question I took it as to mean the stocker CNBG.

That's why I say that the LMLB wouldn't be able to eat the original stocker CNBG - they'd grow too big for the LMB to be able to eat them.

Now Bill Cody is correct that some of the original stocked CNBG might stunt because of a limited food source, but I don't think enough of the original stocked CNBG would stunt to furnish enough calories to be a main food source of the LMB, allowing them to grow large enough, fast enough to be able to eat the stocked CNBG.

Since it takes roughly 10# of fish to put 1# of weight on a single LMB, and a 2" BG would weigh around 3.18 grams I don't think that there would be enough 2" originally stocked CNBG in the pond to make a significant change in the stocked LMB size.

Good comments - my reasoning is the LMB would be able to eat larger invertebrates compared to 2" BG who would be limited to mostly eating zooplankton. . Thus the LMB would eat larger foods and obtain more food volume using less energy to grow more compared to 2" BG.

A little more data, there were 75# of FHM stocked in early May, they pulled off numerous spawns. The BG and LMB were stocked mid September, Late October 55 of Snipes SMB and 8 lbs of GSH. Were stocked. This in approximately a 5 acre pond. We also added crawfish

With the new data then there is a possibility that the LMB could eat some of the 2" stocked CNBG next year.

I’ve posted this before. I have a spring fed creek. Now dry due to our continuing 3 year drought.

About 25 years ago, I decided to introduce bass. I had previously stocked fathead minnows and bluegills. I purchased some 1.5 to 2 inch bass fingerlings. I floated the bag to acclimate them. Then gently released them. I noticed 2 bass minnows side by side. Then there was one with its brother or sisters tail sticking out of its mouth. Cannibalism? Survival of the fittest opportunist? Yep!

The idea in common stocking arrangements (small BG followed by small LMB) is that the originally stocked BG and LMB will not be eaten by fish and will live out their lives populating the pond. It is all the subsequent generations that are managed.

There are many articles with lots of possible variants. This is a cold Minn subset. See end for another text on BG growth.


Bluegill Recruitment, Growth, Population Size Structure, and Associated Factors in Minnesota Lakes
Lakes
Cynthia M. Tomcko & Rodney B. Pierce
Pages 171-179 | Received 08 Apr 2004, Accepted 27 May 2004, Published online: 09 Jan 2


Abstract
To better understand the differences among populations of bluegill Lepomis macrochirus, we analyzed the relationships between bluegill recruitment, growth, population size structure, and associated factors from approximately 2,600 Minnesota lakes. Potential explanatory variables for our models included bluegill year-class strength, growth, population size structure, the relative abundance and mean weight of predator species, physical and chemical characteristics of lakes, summer air temperature, and season. Bluegill year-class strength, growth, and population size structure were more strongly related to each other than to predator and lake characteristics, temperature, or season. Growth of age-6 bluegills was positively associated with population size structure and inversely related to year-class strength, suggesting density-dependent growth effects for adult bluegills. Growth of age-3 bluegills was inversely related to Secchi depth, so early growth and productivity may be linked. Bluegill population size structure was positively associated with length at age 5, as expected from the analysis of growth, and was inversely associated with mean year-class strength. Bluegill year-class strength was negatively associated with population size structure, length at ages 4 and 5, and lake area. Although predator variables were not included in one- or two-variable regression models, bluegill growth was positively related to the relative abundance of yellow perch Perca flavescens, walleye Sander vitreus (formerly Stizostedion vitreum), black bullhead Ameiurus melas, and brown bullhead A. nebulosus and negatively related to that of largemouth bass Micropterus salmoides and yellow bullhead A. natalis. The results suggest that management strategies for improving bluegill growth and population size structure should focus on bluegill recruitment and growth rather than on external environmental factors.

ewest - thanks a lot for taking time to find and for posting the abstract relating to this thread. I was hoping for a different type of information.

The information in the abstract did not tell me what I expected it to provide for percentage of each size group of BG in a population. Nor did it provide an answer to JE Craig's question. I got very little useful practical information from that research project unless I missed something.

I think jpsdad's post was more helpful compared to what Tomcko & Pierce provided in their abstract that to me was too much science, and striving to be scholarly and not enough of a practical summary of all their work.

Bill I emailed you the study.

Look for an article in an upcoming (March/April) PB mag on the topic of BG size distribution.

Timely!

Are you sure you don't have a crystal ball?

Yes, population structure is independent of carrying capacity. If a person looks above, there is a variable for total population. This variable multiplied by the percentage computed the physical number of fish. Average standard weights multiplied by the number of fish in each category determines biomass. Using a total population of 6000 in combo with the total LMB population of 35 determined the biomass. The standing weight/carrying capacity is independent of population structure but highly dependent on natural fertility, habitat diversity, and supplemental feeding.

I appreciate the JE Craig's question and Bill's estimate because it spurred me to analyze balance based on this parameter in ways I never have before. I feel enriched by it because I have more confidence in my understanding than before. (PSD Proportional Stock Density as created by Anderson) I integrated PSD recs for various strategies for similar standing weights (305 lbs fish/acre) to gain an understanding of population limits and population relationships. Under PSD, there are three strategies, Big LMB, Balanced, and Big BG. The numbers are contingent on 305 lbs carry capacity but a ratio can be made of them and this number can be multiplied by the estimated carry in order to understand the population. Percentages can be adjusted based on creel results that estimate population numbers where one has a good understanding of carry capacity (eg understands his water's natural fertility and feed inputs). Below are tables and graphs depicting class populations of a 305 lb total population managed under the different strategies.





The PSDs used to construct the hypothetical populations were taken from this paper and a table from the publication showing different strategies is below.



After all that, those are population structures that are consistent with their respective strategies. The first piece to establishing such strategic populations is the initial stocking. This supports what we already know ... 35 LMB and 1500 BG is a recipe for BIG bass, 70 LMB and 1500 BG can support LMB up to 19" in the first 3 to 5 years. 100 LMB and 500 BG can result in good fishing for panfish. All these for a pond with a carrying capacity of 305 lbs.

The difficult question is how to maintain these population structure into the next decade optimizing recruitment, growth, and harvest.

Initial stocking results in a new water based on common plans (which you noted) are generally successful with good growth in the first stocked generation.

You are absolutely correct that it is always about how you manage the successive generations.

Nice work. Noted as it is for a fixed point in time. After that it is a nightmare to try and measure all the variables in real time. See the upcoming PB article.

Very good discussion. Numbers can be easily manipulated on paper.
Managing fish to where they are in the balance for ones goals is not as easy as managing animals in the barn, in the field or on the pasture. It definitely is not the same as growing backyard chickens. Knowing what fish species and how many of each that are present in the murky depths of a pond are the BIG unknowns that makes fish management very 'tricky' and often performed as a best guess attempt.

Many fishery research studies have been conducted to try to better estimate or calculate how many and what species are present in the unknown depths or zones of a pond or lake. Most often I think the estimates are far less than accurate. The other important factor to keep in mind is that the numbers of the populations are always changing due to hatchings, recruitments and mortalities. Changes are always constant with what is going on under the surface. Good management of the fishery to keep it having high quality fishes is something very worthy to be proud to have and achieve.

Give an iPhone to each one of your fish.

Apple will track exactly what they are doing for every single minute of the day. Problem solved!

That will be a distinct possibility as some form of tiny inserted Apple AirTag sensor at least for some fish in the not to distant future based on the pace of advancing technology.