Local lake fish
Shaw's should still have fresh Great Lakes seafood. www.shawscrabhouse.com
Another place serving fresh Great Lakes seafood, a bit closer to your hotel, is Hugo's. www.hugosfrogbar.com
Whitefish from Lake Superior is perhaps the most common Great Lakes fish served in Chicago; the perch and walleye you mention are also usually on the menu.
I would stay away from Great Lakes walleye. PCB and Mercury levels can be high.
Whitefish from Lake Superior is safe and very good. Perch is good too when you can find it.
I would stay away from any fish that comes out of Michigan or Huron unless they are pretty small.
Can you provide a source for your claims? In the meantime, I would refer people to the following:
It is VERY conservative in its recommendations. Note that none of the contamination issues have to do with mercury. This site also states that contaminant levels in fish have decreased in the past few years.
I do agree that Lake Michigan has the biggest problem with contaminants. Huron and Erie have much less of a problem because they are shallow and the water turns over quickly. Michigan is a deep lake and will hold contaminants much longer than Huron or Erie. Superior and Ontario, also deep lakes, were never polluted to the level of Michigan and do not have its problems.
I was referencing the reports from the Michigan DNR (http://www.michigan.gov/documents/Fis...). Mercury is an issue with Walleye, especially in the southern parts of Lake Michigan that have been heavily polluted by industry.
If I am catching the fish myself so I know the size and where it was caught then I might be more likely to eat it. But in general I like to err on the side of caution and I don't eat local fish.