Fish for dogs: benefits, risks and sensible portions

Reading time: about 8 min

Faddy and Oscar happily eat raw Baltic herring. Irene’s Fenton has so far declined the offer, and Peku, who would usually try almost anything, did not want fish either. Süsi learned to eat it, although he spat it out on his first attempts too. Remembering this story, it is easy to think that dogs who eat fish gain better health and those who refuse it miss out. The reality is more nuanced. Fish can be valuable in a dog’s diet, but it is not compulsory and not every form suits every animal.

I am a great believer in dietary variety, but an equally important question is what a particular fish provides and what risks its preparation involves. Once that is clear, owners can decide whether to offer occasional pieces, choose a complete fish-based diet or consider an omega-3 supplement instead.

What makes fish nutritionally interesting?

Fish can provide easily digestible protein, vitamins B12 and D, selenium and, depending on the species, iodine and zinc. Most attention goes to the long-chain omega-3 fatty acids EPA and DHA. They contribute to cell membranes and the regulation of signalling substances in the body. EPA and DHA are why oily fish can be a justified nutritional addition in some clinical situations.

There is an important distinction: omega-3 fatty acids may help reduce inflammatory responses, but this does not mean that all omega-6 fatty acids cause disease. Omega-6 fatty acids are essential too. No single universally correct omega-3-to-omega-6 ratio has been clinically established for assessing every dog’s health. Many integrative veterinarians nevertheless discuss a ratio of one part omega-3 to five parts omega-6. The composition of the whole diet and the actual EPA and DHA amounts matter more.

Why can a whole fish offer more than a fillet?

A small whole fish provides more than muscle tissue. The head, eyes, brain, skin, skeleton and organs may provide nutrients that occur in smaller amounts or different proportions in a fillet. Bones contain calcium and phosphorus; the liver and other organs contain various vitamins and trace elements; fattier tissues may contain EPA and DHA. This is why I like to see a whole fish as a more varied food rather than simply a piece of protein.

However, having many different tissues does not mean that every fish species, or a fish-only menu, meets all a dog’s long-term nutritional requirements. Nutrient content depends on species, size and whether the fish really is whole. Bones, microbes, parasites and thiaminase in some raw fish also need consideration. Whole fish can be a valuable part of a menu, but is not automatically a balanced complete food.

When can fish genuinely help?

Skin and coat

Studies in dogs with atopic dermatitis have found that adding essential fatty acids can reduce itching and, in some cases, the need for concurrent medication. The effect is generally neither rapid nor equivalent to treatment. The 2026 ICADA guideline recommends considering fatty acids as an additional measure, rather than the sole treatment for a severe flare. Fish itself can also be an allergen for some dogs: no species is automatically hypoallergenic.

Joints and movement

Nutritional support with EPA and DHA may help alleviate some problems associated with chronic inflammation in dogs with osteoarthritis. It remains one part of a plan that includes body weight, appropriate exercise, muscle work and veterinary pain relief when necessary. A limping dog’s problem does not become merely a nutritional issue because fish is added.

Puppies, the nervous system and the heart

DHA plays a role in nervous-system and visual development, which is why it receives attention in growing dogs’ diets. Heart disease and abnormal rhythms are more complicated: omega-3 preparations have been studied, but it is incorrect to promise that fish prevents arrhythmias or treats heart disease. Particularly for an unwell dog, discuss supplements, total fat intake and medication interactions with a veterinarian.

How long should fish be frozen?

Specific freezing figures are useful, but parasites and bacteria must first be distinguished. The US FDA fish-products guidance describes three controlled freezing regimens for parasite control:

• −20°C or below for at least seven days;
• −35°C or below until solid, followed by storage at that temperature for at least 15 hours;
• freezing at −35°C until solid, followed by storage at −20°C or below for at least 24 hours.

These are technical food-safety conditions for reducing particular parasite hazards, rather than a general instruction that makes every fish safe. Actual temperature throughout the process, fish thickness and the time needed to freeze solid all matter. An ordinary domestic freezer at −18°C cannot automatically be assumed to meet these requirements. Parasites and other hazards also differ.

Bacteria are another matter. Freezing may reduce some bacteria, but does not reliably destroy most of them; survivors can multiply again during thawing. Freezing time alone therefore cannot establish bacterial safety. Thorough cooking is a safer option. If you choose raw fish, origin, the cold chain, clean equipment and understanding exactly which risk freezing reduces are especially important.

Is raw fish safe for dogs?

Feeding my own dogs raw Baltic herring has been my practical choice. It does not mean there is no risk. Raw fish can contain bacteria and parasites. Some species also contain thiaminase, an enzyme that breaks down vitamin B1. A diet consisting predominantly of raw fish over a long period can therefore cause serious imbalances. Cooking helps reduce both microbial risks and the thiaminase problem; freezing alone neither kills all bacteria nor automatically makes raw food safe.

A warning often encountered is that salmon causes salmon poisoning in dogs. Geography matters here. Salmon poisoning disease is linked to the bacterium Neorickettsia helminthoeca, carried by certain parasites in fish in the Pacific Northwest of the United States. This is serious, but does not mean that the same parasite cycle is common in Estonian Baltic herring. Here, raw-fish assessment should focus on species, catch location, handling and general bacterial and parasite risks, rather than applying one region’s disease pattern to the entire world.

An important distinction

If you choose raw fish, its safety cannot be guaranteed solely by freezing time. Parasites vary in susceptibility, and freezing does not replace bacterial food safety. FendaF’s more cautious practical choice is thoroughly cooked, unseasoned fish with hazardous bones removed.

Which fish should you choose and how should you serve it?

Smaller species with lower mercury levels and good-quality, thoroughly cooked fish are usually sensible starting points. Sardines, Baltic herring, trout and salmon may be suitable when their origin and preparation are safe. Large, long-lived predators such as swordfish and some tuna species pose a greater risk of mercury accumulation. FDA and EPA fish advice is designed for people rather than dogs, but helps explain differences in contaminants between species.

Remove bones that could harm the dog, and do not add salt, onion, garlic, spicy sauces or butter. Canned fish may also be suitable if it has simple ingredients, no added salt and is packed in water rather than oil; always check bones and other ingredients. Smoked and salted fish are not good everyday dog treats.

Start with a small portion, especially if your dog has not eaten fish before. When fish is simply an addition to a complete diet, all treats and other unbalanced additions should generally stay within about 10% of daily energy. The rest of the diet must provide daily nutrient requirements. If fish is to become a substantial everyday staple, balance the entire ration instead of replacing a large piece of meat with an arbitrary amount of fish.

Is fish suitable for a dog with food allergies?

Sometimes. If the dog has never eaten a particular fish, it may serve as a novel protein in a controlled elimination diet. But novel means new to that individual dog, rather than new in advertising. A dog that has long eaten fish-flavoured food and salmon treats may not be a suitable candidate for a fish-based diagnostic elimination diet. The trial must be precise, exclude other protein sources and follow the veterinarian’s plan. Fish does not itself cure atopic dermatitis or pancreatic disease.

What if the dog simply does not want fish?

There is no need to argue about it. Fenton and Peku remind us that preferences differ. You can try a different texture, an unseasoned cooked piece or a balanced complete fish-based food. If the dog still refuses, assess essential fatty acids in the existing diet. For some dogs, a separate omega-3 supplement is more sensible than experimenting with fish; check its EPA/DHA content, fat amount and quality. Fish oil can also spoil, cause digestive upset and add excess calories.

FendaF’s practical recommendation

Check three things on a fish product: the species and origin; how much EPA and DHA it actually contains; and whether it suits the dog’s overall diet and health. A prominent “1,000 mg fish oil” label does not tell you how much EPA and DHA your dog receives. Raw fish and pieces with large bones are not safe default choices.

Conclusion

Fish is valuable without being a miracle food. It offers EPA and DHA, good protein and certain micronutrients that some other foods provide in smaller amounts. The sensible approach is to look at the individual dog and the whole diet. Fish is one option for Faddy and Ossu. Fenton’s refusal does not itself harm his health. What matters is a balanced diet and safe choices, rather than the idea of eating fish.

Sources

• AVMA: raw animal protein safety in pet food
• UC Davis (2025): salmon poisoning disease in dogs
• FDA and EPA: mercury differences between fish species
• 2017 review: thiamine deficiency in dogs and cats
• Lenox and Bauer (2013): possible adverse effects of omega-3 fatty acids
• ICADA (2026): updated canine atopic dermatitis treatment guideline
• Schäfer et al. (2024): omega-3 and oclacitinib requirements in atopic dogs
• FDA: Fish and Fishery Products Hazards and Controls Guidance, Chapter 5, Parasites; freezing temperatures and times.
• FDA: Are You Storing Food Safely? Freezing does not destroy most bacteria.
• FDA: Selecting and Serving Fresh and Frozen Seafood Safely; parasites, bacteria and cooking.

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