They are somewhat similar to a herring only bigger.
They fight really hard and taste really good.
Almost all the lakes in my neck of the woods have whitefish in them.
Further south you will find Whitefish in almost all lakes that have Lake Trout.
I have caught Lake Whitefish just over 10 pounds but they average 2 pounds or so.
http://en.wikipedia.org/wiki/Lake_whitefish