PondDragon,
One of the things I noticed was that your recaptures did not match precisely fish in the list. So IF the recaptures were fish caught twice on the same day, there may have been variation in measurement(error introduced by the one taking measurements or problems with the measurement equipment). I questioned whether to say anything but now that you voice concern ... I would just say ... continue to practice with your measurements and isolate the cause if there is noticed variation measuring the same thing multiple times. Also, they make weights of a specific mass that you can use to calibrate with. Use your best judgment and experiment until you are satisfied that your measurements are consistent.
Were it me, I would focus on the PKS and manage around them. I don't think you need the GSF at all (with the addition of the right number and size of LMB), but that said, they are playing a predator's role in helping to control some of the recruitment of your desired panfish. Be mindful of that, If you have 30 lbs of GSF in your pond, they are consuming a non-neglible weight of small panfish. Try to gain an understanding (using minnow traps) of how many YOY you have presently in the pond (and their distributions of lengths). Is there a need for GSF predation of YOY over winter? If not, then I would still track the weight and number of the GSF that you remove.
As to the question can you remove only GSF?
IMHO, no. First, I wouldn't add nutrients to your pond to push growth. You've had winterkill before and I would opt to stimulate growth by reducing populations. Removing GSF will free some pond foods for the desired species. It's not going to add the small fish that GSF were consuming (that were too big for PKS gapes). But everything else is, in theory, freed for consumption by your desired species. Based on your initial survey, GSF may comprise around 25% of your adult panfish biomass. This adjustment of increasing foods (per PKS and YP mouth) by less than 25% will be TOO SMALL to get really good growth (if you don't cull PKS and YP too). It will likely also be insuffient to stimulate enough production of YOY for your newly stocked LMB. You need between 35%-45% annual mortalitly of the adult biomass to support superior growth. So the PKS and the YP should undergo that kind of mortality. You want this mortality focused in near quality or quality sizes (5 to 8" for PKS). Fish that are big enough to harvest but that will thereafter grow slow if they are not thinned. Each year, you get a new crop of harvestable fish in those sizes. Reserve some of them for grow out to larger sizes. Invariably, they will recruit more than what would be ideal for growth ... If you don't harvest some.
IMHO, you need to remove 60% of your adult panfish biomass to initiate good growth and good YOY production. So up to 25% of that biomass could be GSF but you also need to take 35% of the existing biomass of PKS and YP. Additionally, You need to add around 10% of your existing adult panfish biomass with LMB that will be large enough by next season's end to consume YOY that have grown all season. Ideally, some of your earlier stocked LMB will have approached 12" in length by season's end. By season's end, perhaps as much as half or more of the adult panfish biomass will be recovered. The pond will still be below its maintenance carry and fish will be growing. You wan't to maintain it in this condition where they have not maxed the carry. This will be done by your predators and yourself through thinning (which might also involve trapping given your weeds). In this state, your pond is more like a new pond (remember when growth was good?) After more discovery, lets discuss how you can manage for the population structure you desire most.
With regard to the species of predator, IMHO it doesn't matter so long as they are stocked at sizes that get you the growth you need this first summer. It may be difficult to source other species in the sizes you need. But whatever size they are going in, if it is working, they should be large enough that 3" PKS are still occasionally on the menu at the end of the growing season. So what I am saying is that there is no magic bullet species that works miracles. Any large gape predator stocking could work and it could fail to produce optimum results if their number and their lengths are not right or if they are ill timed. If your YOY get ahead of your predators, then I would consider that a failure for YOUR goals. You want your predators to stay ahead of your YOY until the predators reach around 11-12" in length. Ideally, they are balanced about there. There should be enough of them so that YOY that ultimately grow to survive predators of this length are not so numerous as to be manageable by harvesting quality panfish. That is probably the definition of balance. Where predators only allow enough recruitment to support a harvestable weight of panfish while restricting the population such that the growth of survivors is sufficient to meet goals and balance with the mortality (both harvest and natural mortality). This may seem overwhelmingly difficult, but balance is painted with a pretty broad brush in terms of acceptable. Good fishing doesn't necessarily mean that growth rates are maximumized. Good fishing can fall within a broad range population structures and harvestable fish sizes.
Let's at least see your second survey before discussing potential stocking rates of LMB. From my perspective, in my own pond, I wouldn't worry about LMB genetics where I am focused on growing panfish. I would go the path of least resistance and do what is the right balance of convenience and cost.
