I was the DNR Fisheries Manager for Columbia Co from 1968 to 1972. During that time we conducted a "chemical treatment project" (fish poisoning) of the upper Fox river, including the tributary streams, down to the dam at Montello. We drew down all the lakes and ponds we could, including Park Lake, but bypassed Swan lake because to try to poison it would have cost as much as the whole rest of the project. The project was not a total success.
Anyway, while Park Lake was drawn down, there was a lot of interest in dredging it. Remember that Park Lake was built in the 1800s as a shallow millpond impoundment on a low-gradient stream with a largely agricultural watershed. Over the years, a LOT of silt was deposited. The DNR lake map depicts conditions at the time - http://dnr.wi.gov/lakes/maps/DNR/0180300a.pdf.
When I worked there, it was very weedy and had a great crappie fishery. Wind drifting across it in my canoe while dragging a minnow on a weighted line produced a lot of meals.
There was also a good population of large bluegills. I used to fly fish for them by Sheep Isand during spawning.
There were some nice largemouth bass and a few Northern pike. There were some carp, but they weren't a problem.
When the lake was drawn down for treatment we had several public meetings to talk about what to do with Park Lake. There was a lot of interest by lake property owners to dredge the lake and get rid of the weeds. Since the majority of the lake is between 5 and 10 ft deep, that would have been a BIG project.
The local interest was to refill the lake as soon as possible, and then use a hydraulic dredge to pump the silt out. The main problems with that was that there was no vacant land near the lake to pump dredge spoils too. Locals wanted to pump into the wetlands on the south side of the lake, which would have destroyed the primary gamefish spawning habitat. We said no. Also the estimated cost of hydraulic dredging was astronomical.
Our suggestion was to leave the lake drained for at least 2 yrs to allow the loonsh_t bottom to dry out, then get a contractor with large earthmoving equipment to come in and haul the dirt out.
That wasn't acceptable to the property owners, so nothing was done until the power dam washed out in 2008. I assume that the main dam on the Fox River was rebuilt with an adequate emergency bypass spillway.
The 1980-90's stocking of walleye and muskellunge were approved based on public demand, not biologically sound management.
Park Lake could be a decent fishing lake for native species, but I'm guessing local politics will prevail...