There are lots of great substitutes for tuna:
-Canned salmon
-Canned herring
-Canned sardines
(all in my stash :-) )
I’m going to try largemouth bass (out of good water) and rainbow trout in Tuna Helper. Bluegill if big enough should work too.
(Chicken will also work in every version of Tuna Helper I’ve tried it in. Although it’s not quite as lean, I prefer boneless thighs for such mixes, instead of breast meat.)