Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations This paper is an absolute must read

I appreciate this "burning" question esshup, as clever as you may think it to be, and I understand that you might be a little confused. I am often confused by your statements and advice as well. For example, I wondered how you could measure (with that accuracy level) the length of a 8.5" BG inside a 20" LMB just by looking at the tail extending from its throat? But in particular, I wondered how you knew to advise PondDragon to stock 75 6" LMB in his 3/4 acre? I mean, how did you measure (with any degree of accuracy) that the pond could supply the consumption biomass of forage needed to maintain/grow those 75 6" LMB? Conversely, its fair to wonder how I could know (with any degree of accuracy) that PondDragon's pond could potentially have a standing weight of 300 lbs/acre of his various forage species? The short answer is I couldn't AND you couldn't either. Although (adding 75 6" LMB - esshup) or (marking 150 GSF/panfish and harvesting until the 100 fish lookback was 50% - jpsdad) is not perfect advice, I assure you and everyone else, that my advice had the least potential to do harm and the most potential to do good.

So let's use PondDragon's (journey/example of good management) as lesson on how to get a grip on the biomass of fish in a pond.

There is truly no work around to understanding one's fish population structure and populations. This is essential knowledge and PondDragon employed the method of mark and recapture to gain a better understanding of what is in his pond, how the population is structured, and made scientific estimates of population numbers from which reasonable estimates of biomass could be made. He followed a path of discovery to understand the CURRENT BALANCE his pond was in. We were able to estimate an adult panfish population between 574 and 750 and estimate a forage brood weight of ~115 lbs. In addition, he made considerable progress on censusing his LMB population identifying two modes of sizes ~7.5" and 13" where the smaller LMB numbered 10 and the larger LMB 2. The sum of the weights is 4.2 lbs of LMB. Although it is not probably all the LMB of these larger sizes sampled, there is a good chance it is a very high proportion of them. He spent a good deal of time censusing fish and if we had knowledge of the fishing effort for the LMB, we could make an estimate of population from that as well and see how it compares with the known number and biomass of LMB.

Is this perfect? No, let me rephrase that. Is this better than knowing nothing at all? Like our combined level of knowledge when you "closed on buy 75 6" LMB" or when I said "mark 150 and remove unmarked until the 100 fish lookback is 50/50? You bet it is better to know something of the demographics than nothing at all. A lot of useful information was discovered by PondDragon. First, we discovered, there is no way on Earth his pond would support an influx of 75 6" LMB. There is just not enough of the right sized forage for them because we learned the pond is already supporting 12 fish larger than that and they are not getting enough forage to grow well. Might have been a good transaction for you, but esshup, there is no way it would have worked out well for Ponddragon. We discovered that his forage brood biomass is more than 20 times greater than this his LMB biomass. And this ... is really all we need to know ... to know that the only solution that will work is dramatically reducing the brood forage weight to increase production of YOY for LMB consumption. Before, commencing harvest of his forage brood fish, his balance looked like this:




Knowing the average weight of PKS and YP is a little over .17 lbs and that PKS can grow .15 lbs/year in his climate, he knows that he can reduce the population by 1/2 and that they have the growth potential to recover that weight over the next 12 months. Knowing that YP can grow faster than that, he knows that removing 1/2 of them will not be excessive either. So PondDragon understands that he can remove ~ 58 lbs of forage brood fish without harming the standing weight potential of his pond AND he knows the brood probably won't recover that biomass next year because there will be much more YOY production and consumption by LMB. This is something Ponddragon wants, he wants larger LMB and faster growth rates for his panfish. This action alone will not permanently fix his pond and it will be an ongoing effort. I think he understands that, but what he is doing is going to influence the next 12 months with effects that support his goal. As a result of his discovery, we learned that his pond could support somewhere in the neighborhood of 140-150 lbs of panfish in the absence of LMB. We also learned that his known population of LMB is probably sufficient to control PKS and YP. We learned, however, they are probably too small to effectively control the production of panfish YOY next year. We explored using an FHM supplement to grow his LMB over the cool months to grow the LMB to sizes that they could control larger sizes of panfish YOY next year. The FHM supplement is conditional to no more than the weight of panfish removed AND as an option ... no more than an additional 15 lbs of FHM. So knowing the pond can support at least 140 lbs of forage fish, we know the standing weights of forage fish going into winter will be below the capacity of the water to carry. So IF PondDragon is successful in meeting his harvest goal and forage supplement goal he will have transformed the estimated balance above into this:



As the surviving fish consume FHM over the winter they will grow. Particularly the LMB will grow which have significantly greater growth potential than the panfish. They will consume greater proportions of their body weight than the panfish and log proportionately better growth. If in the end the split of FHM go 50/50 to panfish and LMB and if they combined consume all the FHM by May 1st next year ... the balance on May 1st will look a little more like this:





So if he succeeds in meeting his harvest and supplement goals, he has a pond completely transformed from one with very poor balance to one of remarkably better balance next spring. His metrics next year at this time will be remarkably better than they were this year. Of course, it does depend, it depends entirely on making the adjustments and surviving the winter without winterkill. Going forward ...he will still need to be taking actions to maintain good balance and fortunately he has the tools ... and knowledge ... to continue to mold his fish populations to balance goaled growth with the pond's productivity.


So how important is the accuracy of the biomass estimates? Less important than not having the biomass estimates at all. Having discovery and making best effort estimates is BY FAR much better than "willy nilly" stocking 75 6" LMB. It's not clear to me if you are trying to declare fault with making estimates of biomass (or their accuracy) to suggest such efforts are a waste of time. If that is what you are trying to do, esshup ... it's just a strawman ... with an alterior motive. Do you have a "burning" need to convince people they can't make useful estimates of biomass and populations? How would it benefit you? I mean particularly you? If on the other hand ... you agree that effective/useful estimates of populations and biomass can be made and that they are more useful than knowing nothing at all ... I would appreciate some support on what I've been sharing about population and biomass management strategy.