Batter & fry will help with the flavour of old fish.

Even something like Mrs. Dash will help.

How 'bout expanding your table fare to include other species if you can't seem to catch any small walleye?  Not a lecture, just a question. 

The only time I am going to eat a walleye over 3-3.5 lb is if (s)he is not going to survive the landing/dehooking.  Walleye and lakers are by far my preferred forage though I do like to limit my impact on the brood stock as much as I can.  But that's my personal preference.  As Wally will tell you, you can keep anything and everything you wish that's within the legal limits.

Bass and Pike are very tasty from clean lakes.  Learning to remove the y-bones from pike is a valuable skill though it can just as easily be done as you eat it if you know the trick to exposing them.  In my mind, pike from these waters are every bit as tasty as walleye and I challenge anyone to tell the difference in a blind taste test. I cook them exactly as I would a walleye.

Here is how to de-bone a pike as you eat it.  I've been doing it this way for 40+ years and you'll be an expert after just a fillet or two:

(You need to Login or Register to view media files and links)

Bass are essentially overgrown panfish.  If you keep the size reasonably small on the bass (usually not a problem on most any lake  ) it's almost identical to eating crappie.  Very tasty bronzed or breaded.

Again, not a lecture, just hoping to broaden your gustatory horizons.

I've heard chowders are good for the bigger tougher fish. i've never tried this method but hope to report positive results come mid September Otherwise I think maybe fish tacos would be a good choice for tougher fish or maybe breaking it up and making ceviche?

I agree that tough fish usually means overcooked fish.
Sometimes people describe big/old fish(meat) as being tough when what they really mean is that it has a stronger flavor( gamey)?

Poaching in a seasoned liquid is a good way to handle toughness/gamey issues.
You don't want to overdo it though or you'll end up with fish/meat that resembles a rubber tire.
Poach until fork slides in with little resistance and call it good.

Kinda like cooking huge pike. Nail it to a board, roast over fire, remove fish. Eat the board!