Compare them on four axes: fat level, fatty acid profile, novelty for your dog, and smell. Fish recipes tend to be leaner and richer in the long chain omega 3 fats EPA and DHA. Poultry recipes are usually milder, cheaper and more familiar. Both can be complete and balanced, so neither is inherently the better buy.
The axes that actually differ
Most fish versus poultry comparisons collapse into vague talk about which is healthier. That question has no answer, because both are complete diets when formulated properly and the protein source is only one variable among many.
The differences that genuinely affect your purchase are narrower and more practical. Fat content and calorie density differ, because white fish is typically lean while poultry varies a great deal depending on whether skin and dark meat are included. Fatty acid profile differs sharply. Novelty differs, which matters if your dog has been eating chicken for years. And smell differs, which decides more meals than owners like to admit.
Price differs too, and usually in the same direction: fish costs more, both in the sea and on the shelf.
Fat and fatty acids
This is the real distinction. Poultry fat is dominated by omega 6 fatty acids, chiefly linoleic acid. Fish brings the long chain omega 3 fats, EPA and DHA, which dogs cannot manufacture efficiently from plant sources.
Those fats are why fish recipes get talked about for skin and coat condition, and why fish oil turns up as an added ingredient in recipes built on other proteins. It is worth being precise here: EPA and DHA are also used therapeutically at doses set by veterinarians for specific conditions, and that is a clinical decision, not a reason to pick a recipe off a website. If a vet has recommended omega 3 supplementation for your dog, ask them what dose they want and how a diet change interacts with it.
White fish such as pollock, haddock and cod is lean, so a white fish recipe tends to be lower in fat than a poultry recipe with skin included. Oily fish such as salmon sits at the other end and carries considerably more fat and more EPA and DHA. Reading which fish is named matters more than reading the word fish.
Novelty, rotation and fussiness
Chicken and turkey are the two most commonly fed proteins in dog food, which means most dogs arrive at a fresh diet having eaten poultry for their entire lives. Fish is comparatively novel for a lot of dogs, and novelty is useful in two separate ways.
For a dog who has become bored, an unfamiliar protein often restores interest in the bowl on its own. For a dog under investigation for a food reaction, a protein they have never eaten is a necessary component of a proper elimination trial, although that trial has to be designed and supervised by a veterinarian rather than improvised from a product page.
Novelty cuts both ways. Some dogs dislike fish outright, and a strong smelling recipe is a harder sell to a cautious eater than a mild one. Buy the smallest quantity you can the first time.
Smell, and who has to live with it
Fish recipes smell like fish. That is a feature for the dog and a cost for the household, and it is the most common reason owners abandon an otherwise successful fish recipe.
Poultry recipes are mild, which suits shared kitchens and owners who are sensitive to the smell of thawing food. If several people feed the dog, this is worth asking about before you commit to a large order.
Setting the two side by side
Some recipes refuse the choice. The My Perfect Pet Turkey and Wild Salmon Blend lists both turkey and salmon in its live product data, along with added fish oil, cranberries, green beans, potatoes, spinach and sweet potatoes. That combination gives you a poultry base with the fatty acid contribution of fish, which is a reasonable answer for a dog who likes poultry but whose coat you want to support. Exact fat and calorie figures are not published in the description and sit on the pack and in the nutrition facts sheet instead.
Whichever direction you go, the claim that settles adequacy is the same for both. The FDA's explanation of complete and balanced pet food is a short read and worth doing once.
Frequently asked questions
Is fish better than chicken for dogs?
Neither is better as a category. Fish contributes more EPA and DHA and is usually leaner, while poultry is milder, cheaper and more widely accepted. A complete and balanced recipe built on either will meet a dog's nutritional requirements. Choose on your dog's diet history, your budget and what your dog will actually eat.
Which fish is used in fresh dog food?
Most commonly Alaska pollock, cod, haddock, whiting and salmon. The first four are lean white fish with mild flavour; salmon is an oily fish with substantially more fat and more omega 3 fatty acids. A recipe naming its species is giving you more information than one that simply says fish or ocean fish.
Can I feed fish to a dog with a chicken allergy?
Fish is a common choice in that situation because it is unrelated to poultry, but a suspected food allergy should be confirmed through a supervised elimination trial rather than assumed. Cross reactivity is not the issue with fish; the issue is that most owners have not actually established which ingredient is responsible.
Does my dog need a fish recipe for omega 3?
No. Many poultry based recipes include added fish oil or algal oil to supply EPA and DHA, which achieves the same thing without a fish flavoured meal. Check the ingredient list for an added oil source rather than assuming the main protein determines the fatty acid profile.
Will a fish recipe make my dog smell?
The food smells noticeably of fish, and some owners report a faint fishy note on the breath. It does not generally change body odour. If the kitchen smell is the objection, a poultry recipe with added fish oil gives you most of the nutritional benefit without it.
Related reading: Pollock for Dogs: The White Fish Behind Many Fresh Recipes and Single Protein or Blended Recipe: Which to Buy First.