I am renovating a ~three acre fish pond in far southern Georgia. After it's initial construction and stocking ~30 years ago, it was decent fishing for several years, but then it seemed like we started catching fewer and generally older/larger fish. I have always had the sense that it held fish alright - the water is on the acidic side of things, which is typical for this area, but invertebrate and minnow populations always seemed healthy - but that they simply were not reproducing. This was reinforced when, about seven to ten years after the pond was built, we had to drain another pond and we transferred a good number of ~1 to 5 pound bass to this pond. We continued to catch what I suspect were these same fish for years afterwards (increasing in size, but decreasing in number as time went on), but very rarely caught any smaller fish. Ultimately, the quantity of fish declined so significantly it really wasn't worth fishing. The last successful fishing outing that I heard of was for catfish

I attribute this to a mucky bottom. When the pond was built, a small "valley" was simply dammed, and while I was not involved, I believe the sides were cleared of vegetation below the water line, but otherwise basically left as is - forest soil. I get the sense that over time, the soil from the sides has slumped - this is fairly readily observable in a couple spots, and I assume present elsewhere less dramatically. Additionally, over the past 10-15 years, water hyacinth overtook the pond and then was killed off sporadically, contributing to a build-up of organic muck. Wading, prodding and generally mucking about was enough to convince me that there was virtually no exposed clay or sand on the bottom - only a layer of muck and fine silt from 6" to 1'+ deep. We've now drained the pond, and confirmed this. So I have a number of questions:

1) Does my theory that a mucky bottom has essentially prevented reproduction hold water?

2) Assuming we scrape the bottom to remove the existing muck, are the sides going to continue to slump, or would the new slumping likely decrease significantly given that the area has been submerged for thirty years (i.e. would most of what would slump have already slumped)?
Would cutting the sides back to clay prevent this (this being south Georgia, it's there somewhere, and often not very deep)?
Building up and and compacting the edges?
Lining the areas where slumping is most significant with 1'-2' chunks of limestone?

3) If preventing the slumping isn't feasible, could raised mounds within the pond basin or concrete culverts scattered around possibly provide adequate bedding? How many and what size? How much bedding area is needed to make a three acre pond productive?

4) What would you expect in terms of cost? This is ~2 acres with ~0.5'-1.5' of muck that would need to be removed (so worst case ~4,800 cubic yards), plus we would like to excavate another ~3/4 - 1 acre that is too shallow by about 2'-3' (so again worst case ~4,800 cubic yards of sand/clay soil). There is little place to put any of this material within the contours of the pond or around the edges, so it will have to be hauled ~200 yards under conditions that would likely require off-road dump trucks (up what passes for a steep hill around here, without a proper road).

5) Any suggestions on execution? How best to dry out the muck prior to getting heavy equipment in? Would slurrying and pumping it out possibly be a viable option, less expensive than excavators and dump trucks?

6) What is minimum recommended depth for south Georgia? I can find pretty specific figures for other areas, but not here. (This is not generally an issue for most of the pond, just potentially one small section).

A lot of questions, I know, and any insight is appreciated.