Given the size progression of 1 1b per annum with an ultimate weight of 9 lbs we might consider this ultimate weight to be achieved in the 11th or 12th year. So a suitable question is, "How many 3 lb LMB do I need to recruit every year?" It is equally suitable to ask the question, "How many 3lb bass must I limit recruitment to?" If you have a given number of LMB in each year's recruitment and assuming no cropping of LMB >3lbs will occur until they die in 11th year, one may construct a spreadsheet that provides an estimate of the annual forage needs of the 3lb+ trophy selected LMB. Below is a spreadsheet that outlines the demand that I think might work with tubguy's BOW.
In the spreadsheet you will find that if limited to 3 LMB/acre/year, in the seventh year, there will be 21 LMB/ACRE >3 lbs and averaging 6 LBS. A highly successful trophy BOW IMHO, particularly for a northern pond. These will require 675 lbs of forage annually for this segment of the population. The scenario assumes that one harvests 9 lb LMB or they die in that year without consuming a lot of forage.
Now the question of how many of the original stockers to harvest before the next growing season gets into full swing. Let's make an estimate of how much forage tubguy's BOW produced in the last year. To some degree, this is a WAG but not entirely WAG. We have the benefit that his BOW is two years old with a known number of LMB stocked at inception. We could use typical first year mortality to estimate the number of original stocked LMB surviving and from this number estimate the forage production required to grow the LMB to their current size. I will assume that that 80% of the original stocking survived the first year and since he has only harvested 5 of the original stocking ... I will ignore the harvest figures.
So the figure is 80 LMB/ACRE. I will assume 1.5 lb for first year growth and 1.5 lbs for second year growth. Tubguy chime in if this is wrong. So over the past year forage production is estimated:
LBS FORAGE= 80*1.5*5 + 80 *1.5*10 = 1800 lbs/acre
OK ... so this is a BIG number and it vastly exceeds the standing weight of bluegill. Even so it highlights how productive a heavily cropped BOW can be. Up to now there are no trophies and the majority of BG have been cropped at 2"-4". As these were cropped, more rapidly replaced them and indeed a multiple of BG carrying capacity was produced. This tells me the BOW could probably support the grow out in the spreadsheet below. Even so, it is important to recognize that the LMB of the projected grow out need 4" to 7" BG and the BOW cannot produce the same poundage of these annually. Right now, the BOW needs to produce BG in the 4" - 5" range. This need for larger BG will reduce the production in lbs of forage because BG also have maintenance requirements and convert food better when they are smaller. So what number to use? I don't know. But a smaller number should be used than the 1800 lbs produced this year and I will assume 80 percent of this year's production or 1440 lbs /acre.
Now to grow 80 LMB/ACRE from 3 lbs to 4 lbs, what will it take in forage?
LBS_FORAGE = 80*3*5 + 80*1*10 = 2000 lbs
If we take our estimate of forage production and divided it by that required we get .72 and if we multiply that number by the 80 we get 57 fish. Based on this combination of assumptions and evidence we can construct a plan that is an "educated guess" which may only be a little better than a WAG but it is a plan based on known principles and reasonable assumptions.
If it were me, I would be just a bit more aggressive to factor in the classes of LMB that are in the recruitment stage. I really do think an appropriate number to harvest would be 30 LMB per acre of the original stocking(assuming that ~ 80 LMB/acre still remain)
Last edited by jpsdad; 11/30/1811:42 AM.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
