Depends on what Zone you are fishing and wether you have the Sport licence or the Conservation licence.
If you go with the Sport licence you can pretty much keep any fish you catch. There are exceptions like Sturgeon that have a strict release only policy in certain zones, like 6 and 9.
Most regions you can keep everything except these exceptions, that includes:
Walleye, Sauger, large & small mouth bass, pike, musky, perch, crappie, sunfish, all the variets of trout(brown, rainbow, lake), pacific & atlantic salmon, whitefish and channel cats.
When in doubt check and adhere to the regs at all time.
Regs can be found here:
http://www.mnr.gov.on.ca/en/Business/Le ... 63615.html
Dirk....