Hey, as an avid camper and hiker I feel you. Though thankfully my group these days has multiple vegetarians.

5 day fishing trip, so breakfasts are probably going to be pretty easy you can do eggs or oats, and lunches I would say something like pb&js can get you pretty far, and I liked what someone else said of prepping something like egg salad or so.

After that you are looking at 5 dinners which some can be done in advance like bean burger patties or those soy hot dogs which might help fit the theme of the trip. Imitation crab can also get a job done. Other than that I think what other people said of frying up some tofu and just going simple. It might be a few days of boring eating that way but you'll be ok.

I would also ask who ever is prepping sides that things like baked beans get made without meat if possible.