"I estimate that on the low side (higher catch rates) that you went from 21 LMB/acre three years ago to 5 LMB/acre. That's a difference of 16 LMB/acre. So, have you removed around 48 LMB? " wrote jpsdad
You are some relation to Carnac the Magnificent? I would like to understand how you figured that out.
I have removed 50 LMB & 7 brown bullheads RWs also at 75%. During the past 3 years, the number of YOY LMB that I have seen or caught, I can count on one hand. I do believe in the 80/20 rule. My little corner of the pond has the most structure & it is where the BGs are fed. hence sooner or later the LMB more to this area. My gut says that there may be less than 5 LMB/acre now.
No, not related to the Magnificent Carnac, LOL. The chart ewest posted displays vulnerability to angling. The units are (catch/hour) per (LMB density). The density in the chart is number per hectare but I like to use number per acre and so the number is adjusted to acres. The parent generation is .033. Soooo, if you know the catch rate, and if the vulnerability is like the parent generation (the higher vulnerability to angling) .... to estimate the population ... divide the catch rate by .033 and it will be an estimate of the density per acre. Now it isn't fool proof. Some people are better at fishing than others for example. But it is a place to start for sure. What we did, was determine if the evidence of your total catch is consistent with the estimates (including our assumption of vulnerability). That feedback suggests that you may have decimated your LMB population following forum advice.
What I am now seeing & what is supposed to be happening, the two just don't make good sense. I have a much larger population of > 8" quality BGs than I ever had of quality LMB. Removing more LMB no longer made good sense as I began to wonder if there was no longer an abundance of LMB to remove. Something else appears wrong. After reading & re-reading PondDragon's post & the Must Read post I began to wonder if excessive large forage biomass is the problem.
You are on the right track now. You have figured it out.
It is important to understand your forage population and biomass. So that is what Ponddragon did. He also marked his LMB, and has good info on what he knows is in the pond. Estimating standing weights, he has a good understanding what he needs to take out on the forage side.
You should do something similar to make a good estimate of your standing weights (both Forage and LMB). Then we can make estimates of the poundage that needs to be removed. If you'll do what Ponddragon did, I can do more to help you. If you read the thread carefully, you'll see how the picture became clearer with more data. For example, in the beginning, I was off on the weight of forage the pond was supporting. When Ponddragon expressed doubt to that number, we decided to actually make an estimate with mark and recapture. A lesson there is that even though his pond probably mobilizes enough nutrients to carry higher standing weights ... the mix of veggies growing on that mobilization won't carry that weight. The profuse chara lowers the forage potential relative to a good bloom. It doesn't matter, he can manage the pond just like it is .... but he needed to understand what that "just like it is" ... actually is ... in terms of forage potential.
The biomass (LMB & BnBH) that I removed is now turned into BG Biomass?
Not exactly. A pond has a forage potential ... but ... a pond doesn't have an independent LMB potential. The standing weight of LMB DEPENDS on the consumable forage. And not what some forum participants think is consumable. It's what is actually consumed. The LMB don't care about our opinions. They eat what they can ... when they can ... and our opinions don't matter to them. If a pond appears to someone to be full of forage and LMB aren't in good condition and growing fast ... then someone has the wrong opinion about their forage. They are just wrong because the LMB are not in agreement with their assessment. The evidence says otherwise.
So LMB are the tail and the BG are the dog. LMB depend on BG ... but ... BG do not depend on LMB. BG are the horse and LMB are the cart. What determines the standing weight of LMB is the weight of BG they ate the prior 12 months. It is no more complicated than that.
Removing the LMB as you have been advised ...lessened the predation and what happened is that more BG grew past them and now they along with the others occupy more of the BG Potential. Since they are too large to be good consumable forage, they occupy potential that 3 years ago produced forage and the pond can now only carry the reduce number and biomass of LMB you now have. You know this because they have poor condition. You can't fix this problem by only adding LMB. You know that you must remove the forage fish that the LMB cannot eat so that there will be more forage produced that they can eat. Only then could you add LMB that could grow.
If I continue as I have I will have a BG only pond with few or no LMB?
I think this is possible, but I also think you have enough knowledge now to see that this does not happen.
What is the most effective size forage to remove? All BG caught >6" ? Males or females? Keep large Males for greater survival of fry & fingerlings. Stop when I am catching BGs 40% <6" & 60% > 6"?
I would not remove BG that have good profitability. Nothing under 25% of length of your average sized LMB. There are two aspects to balance. One is biomass while the other is population. So what you want to do is reduce the biomass of BG brood to less than 50% of the potential so that when they grow over the next 12 months they will occupy no more than 50% of the potential. To do this effectively, the population of brood should be restricted enough that they grow near their potential of annual growth. If there are too many brood, they will want to grow each at their potential if they can. So a 50/50 male/female mix wants to grow .37 lbs/year ... that means ... 200 brood fish want to grow 74 lbs but 1000 brood fish want to grow by 370 lbs. See the difference. With 200 brood fish, you need to maintain their weight 74 lbs below your target proportion of the potential but with a 1000 ... what happens ... is that it is untenable ... they can't grow at their potential but grow much more than the 74 lbs and so increase in proportion to the potential by much more ... which means ... they squeeze out consumable forage production and the LMB suffer for it.
