I think you can start YP harvest when you are seeing presence or good YP recruitment of 4"-6" perch. Those fish will take the place of the 8"+ that are harvested. Number to harvest is dependent on several things and assuming a good hatch of eggs each spring. 1. Relative number of YP you want in the pond, sparse, medium, or dense easy to catch harvestable sized YP. 2. Number of WE. Obviously the 'stronger' the WE population the fewer YP will be present due primarily to lower recruitment of 6" YP from predation by WE. I prefer the dense easy to catch YP thus for this the WE should be stocked at the lower rate <30/ac. 3. Productivity. The more productive the pond the more YP will be present and the more that can be harvested. Pellet feeding really helps boost the YP harvest rate to around 50-70 lbs /ac per yr. No pellet feeding then the harvest rate drops to almost one half. First harvest from 300 stockers after they reach 8"-12" can easily be 30 fish. Heavy first harvest would be 50-80 YP. Again number to harvest depends on strength of the 5"-8" class of YP.
I harvest about 50 lbs of YP/ac per year and the harvest could be heavier (70-80lb/yr), but I prefer higher numbers of larger YP to be catchable.
WE are much easier to add than to remove. Plan on each WE to eat at least 200 small fish per yr. Half or more of them could be YP. If you are mainly interestred in YP, I would start with lower numbers of WE and then add a few every other year based on how many WE are harvested once they get to 15"-16". I would harvest any WE over 15" and then replace them with restockers (7"-9").
Watch your catch rates of YP - keep records of angling success, sizes, and numbers caught per hour of angling. Data will show trends. Visually watching what size YP are coming to pellet feed is a pretty good indication of population structure. If catching of smaller YP is increasing for a couple years, then more harvest or predation pressure is needed for younger YP. If angling results in usually catching YP larger than 8" then things are IMO balanced. Watch these things annually and make adjustments as appropriate. You will see differences in catch rates from year to year. Compare your records. While working with it you will get a good 'feel' for a proper balance. Generally inbalance does not 'go south' all at once, it is a gradual thing over a couple years and generally shows up in catch records if one has good records and good control of who fishes and what is harvested.
With lower WE numbers in 3/4 ac (10-20), I try to annually trap and remove some smaller 3"-6" YP, if the traps catch good numbers of this size of YP. Build or buy at least a couple fish traps, one with 1/4 mesh and one with 1/2" mesh as described here on the forum. I have about 10 fish traps of various sizes. Maybe remove the largest GS when caught in traps or by angling with small hooks (#12-14) and small pieces of worm. You may also catch small YP this way which can indicate their relative numbers. I annually do this around early July but since you have pesky GS this technique is a little more difficult, frustruating and tedious.
Last edited by Bill Cody; 06/27/11 08:40 AM. Reason: Minor fixes and clean-up
