Okay, so my daughter has a half Dogo/AM Bully who is white and pink and has horrific allergies to everything except Fish and Rice and Fish and Sweet Potato, so she winds up buying a specialty feed from the vet that has these two examples. He's good on them, but it is expensive.
Some here would suggest feeding raw, which is a huge investment in time and effort and a steep learning curve. (Also for me the "ick factor.")
I suggest a visit to the dogfoodadvisor.com and look for something along the fish line for protein and of a high rating. 4 out of 5 stars, 5 out of 5 stars.... Personally, I feed Acana and the Beef/Pork/Lamb (?) mixture, BUT, I also cook her meat for her: she gets both. There's a lot to the science to creating a good dog food, especially, how the production is done...low heat production stops the production of acrylamides which are toxic to dogs. Orijen also creates a great dog food, and they have a very good fish formulation.
We tried Bailey out on a lot of them, but she prefers mammal-type meats, so we are presently using the one listed above.
It is expensive, BUT, it isn't full of fillers and undesirable ingredients of dubious sourcing, so you end up feeding less. Less if definitely more with this one, you are getting great nutrition. Of course, this is just my humble opinion based on a four-year-old Mastiff and she only ever got itchy with chicken-based kibble; however, she never gets itchy on real BBQ-style chicken. We get one from Metro every Tuesday and she gets several feeds from it. Loves, Loves, Loves to get her Cluck On!
I should mention, before I get kneecapped about it from the membership, that we do not advocate for any particular food maker. We do suggest a visit to dogfoodadvisor.com, but again, with a stipulation. There are two levels there (I haven't visited in quite awhile, but I've been told), one level is open to the public, there is a more specific or premium level available for a fee, which supposedly gives you the company's owner's best bet or best opinion. Don't know, haven't checked it out. I don't know if "He" responds to particular inquiries, but....who knows. Give it a go, it's a great place to start.