@mdwest the reason Wisconsin buys Cod and Walleye for fish fries is because of their consumption levels. In some counties, 80-90% of all living souls go out for Friday night fish fry, every Friday, 52 weeks a year.
Absolutely, fresh line caught Walleye, Crappie, Bluegill, Burbot, and Whitefish are absolutely classic fish to "Fry up" at deer camp if someone brings some they caught earlier in the year. But "frying up" fish with shore lunch is linguistically a bit different than a "fish fry" or "friday night fish fry". The latter are almost always a light and fluffy beer batter and the fish is 90% of the time Atlantic Cod, 10% of the time commercially harvested Walleye.
If it wasn't for all the world's oceans, Wisconsin would run out of fish every Friday.
My county in WI is one of the most rural and smallest population centers, about 14,000 people and most of those are students at a State university. Nonetheless, in my sleepy county I can think of 20 bars and restaurants that have "Friday night fish fry".
But anyway, if anyone wants a light and fluffy batter for any fish, it is really hard to beat a simple google search for "Alton Brown's Beer Battered Fish". If you want that airy batter that fluffs up, that's the one.