Texas,

I doubt I'm the expert advise your looking because this is only an interest and what I tell you is what I have read or learned from others experience. But, I will give you some feedback on you ideas.

First, Is your goal to make a trophy bass lake? If not, what are your plans?

...Idea: I want to draw down the water level about 4 feet to add structure, dock repair, kill off vegetation, clean shorelines dig out some deeper channels...

...Question: During the winter there are roughly 700 ducks come in. Along with cormorants, pelicans and various other birds. I also have a high turtle population. With consolidation of fish in a smaller area will they kill most of the fish?...

Ducks are not your problem. Cormorants are and many posters recommend the boom, boom option. They are protected so your call. One guy has trained his dog to bark when any type of water bird drops by the pond. It's my understanding that turtles are not an issue for your fish. If you don't like "em, do a little target practice. I have a buddy that has access to a very large property with a lot of water on it. It's bottomland, so swampy, with river and lakes. Riding the four-wheeler and taking long-range shots at turtles with an assault rifle is highly entertaining for someone who likes to shoot.

...Question: What makes better structure (trees, tires, etc.)?...

That depends on what you are attracting. Minnows and small fry like Christmas trees, which in turn bring in the minnow predators. I'm think white perch/crappie here. Bass like vertical structure near deeper water, say tree stumps, your pier posts, fallen trees etc. Bottom line most structure is good, but take care in the amount and location. Don't overdo it.

...Question: Is dropping the water level that much too much? It would expose roughly 35%...

The question from me is how deep is your lake? If its only averages say 6 ft you may get more than 35% exposure. This is probably OK and your bass will have a good opportunity to chow down of the feeder fish that they are bunched up with in the bowl. It does bring the issue of cormorants back into the picture.

...Currently I have high population of LMB, a small population of perch, about 5 carp, and have seen a couple of catfish. I have only been doing a catch and release this year to record everything. The bass are under weight due to what I believe is lack of food. I am correcting that and supplemental feeding the perch...

If you have the budget to survey this lake by a professional, you should do it. You will be told what shape your fish population is in and how to fix it to meet whatever your personal goals happen to be. Short of that, buy the “Raising Trophy Bass” book from the Pond Boss, I did and it makes reference to every question you've posted here. It is very informative.

I assume that you mean bluegill when you say perch. If you want to help the bass consider adding, adult feed trained bluegills and threadfin shad. I have another buddy with a 50-acre lake in SW Mississippi. It was an older lake when he got it and had an existing population of channel cats, bluegills, and scrawny bass. He stocked big numbers of fish, including adult bluegills, fingerling bluegills, thousands of shad, fingerling bass, and approx. 1000 8-inch Florida yearling bass. That was 6 to 7 years ago and 10+ pounders are now routine.

After all of that: Hire a professional survey. Bob Lusk may even be able to do it for you.

gw