What fish should I add to Raw Meow Mix?
None.. and I'll explain why that's not the answer most people expect.
When did you last see a lion fishing for his dinner?
Cats are obligate carnivores. Their ancestral diet is land prey.. small mammals, birds, the occasional reptile. Not fish. The idea that fish is a natural or appropriate protein base for a cat's diet is something the pet food industry built, not something biology supports.
A domestic cat's nutritional requirements were shaped by millions of years of hunting things that did not live in water.
Raw Meow Mix is designed to be paired with appropriate protein sources. Chicken, turkey, roo, pork, beef, lamb - land animal proteins that reflect what a cat's digestive system is actually built around. Fish is not the base. It never was.
"But I've seen videos of cats eating fish at the seaside in Greece."
Yes. Those cats are almost certainly feral, unfed, and eating what is immediately in front of them because that is how survival works.
Opportunistic feeding is not the same as optimal feeding. When an animal is hungry and food is available, it eats the food. That is not biology endorsing the food. That is an animal doing what it needs to do to stay alive.
A feral cat adjusting to a coastal environment and eating fish when nothing else is accessible tells you exactly nothing about what a domestic cat in your home should be eating. You would not look at footage of a stray dog eating from a bin and conclude that bin food is an appropriate diet for your dog. Same logic applies here.
Why is fish in almost every commercial cat product then?
Two reasons. It is cheap. And it is addictive.
Fish is one of the most cost-effective protein sources available to pet food manufacturers. It is also intensely aromatic, and cats respond powerfully to smell. A cat fed fish-flavoured food regularly becomes strongly conditioned to that flavour in a way that makes them reluctant to accept anything else.
That is not an accident. A cat that will only eat fish-flavoured food is a cat that keeps buying fish-flavoured food. Palatability that creates dependency is very good for a company's revenue. It is not particularly good for your cat.
The prevalence of fish in commercial cat food tells you about margins and market strategy. It does not tell you what cats are designed to eat.
So where does fish fit?
Fish has one specific job in your cat's diet: omega-3 fatty acids. EPA and DHA, the long-chain omega-3s that support skin, coat, brain function, and inflammation management. Cats cannot convert plant-based omega-3s like flaxseed into usable EPA and DHA, so we need an animal source.
That source is small oily fish - a few sardines per week, canned in spring water, no added salt - or green lipped mussel. Raw Meow Mix already contains this.
One note on older cats: seniors can benefit from a little extra omega-3 support, particularly for joints, coat condition, and cognitive function. If your cat is older and already eating a balanced diet, adding a few extra sardines is not going to cause a problem and may actually help.
Why not more, and why not raw?
These are two separate questions and both need answering clearly.
On raw fish: certain raw fish contain thiaminase, an enzyme that destroys Vitamin B1 before your cat can absorb it. Thiamine deficiency is serious - it causes neurological disease, seizures, and cardiac dysfunction, and it moves faster than most owners expect. It can be fatal. Thiaminase is deactivated by heat, which is why the form we use is canned in spring water, not raw fish tossed into the batch.
Worth knowing: the same destruction of B1 happens with sulphite preservatives 220 and 223, commonly found in supermarket pet mince. Different cause, same outcome. If you are buying raw mince for your cat, the preservative label matters.
On quantity: even with the thiaminase issue resolved by using canned, fish fed in large amounts over time creates its own problems. Fish is high in polyunsaturated fatty acids, and a diet heavily weighted toward fish will deplete Vitamin E over time, which can lead to steatitis - inflamed, painful fat tissue. It is a documented condition in cats fed fish-heavy diets. Tuna specifically bioaccumulates mercury across its long lifespan, which adds up in a small animal fed it regularly.
A few sardines a week, canned, as part of an already balanced diet: none of these risks apply. The volume simply is not there.
The bottom line
Fish is not a protein base. Your cat's diet needs to be built around land proteins. Fish has one role: contributing to the omega-3 requirement - a few canned sardines a week, or the GLM already in Raw Meow Mix.
If you are eating a tuna sandwich and your cat is staring at you with that look, a small piece is fine. A bit off your fish and chips, the occasional scrap from your plate. The difference is between a treat from your plate and making fish a structured part of their diet. One is fine. The other is where the problems live.