Some ingredients that Franklin needs requires you giving fish to villagers that have a chef's outfit. Will villagers be wearing that shirt or do you actually have to have a villager wearing a chef shirt to get those ingredients?
They will be wearing the shirt on the Harvest Festival day. You do not have to mail them one, give them to one, or have them wear one or display it or even just have it in their possession in order to get ingredients from those villagers. Hope that answers your question.
Thonky's Guide has a list of all the fish you need for the recipes.
Missing from the list are river fish your villager might ask for.
Black bass,Dace,carp,crucian carp and rainbow trout are a few that they ask for.
Last time I played I forgot to catch Dace ahead of time. The villagers kept asking for a Dace. And it took forever to catch one.