White cat in front of a plate with fish
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Can cats eat fish?

By Ashley Murphy Content Writer

Updated on the

Cats love a bit of fish, but is it good for them? How much fish can a cat eat? And what happens if they eat too much? Here’s what you need to know about your cat eating fish.

Although they really like the taste of it,  Fish is not part of a cat's natural diet. With the exception of a few species, wild cats don't eat fish at all; nor did their evolutionary ancestors. This doesn't mean that fish is "bad" for your cat. Rather, it's just not very "good" for them. It lacks many of the essential nutrients your cat needs, like calcium, sodium and iron. 

So can I give my cat fish?

But this doesn't mean you need to put your kitty on a complete fish ban; you just need to limit the amount they consume. Most fish is OK for an occasional treat, but it shouldn't make up more than 10% of your cat's diet.

Remove those fish Bones

When it's time for a fishy treat, make sure you remove all the bones, including the tiny ones. Even these can get stuck in your cat's throat or digestive system. This will be very uncomfortable for the cat, but it can also lead to health complication like internal bleeding. 

Can I give my cat some raw fish as a little treat? 

Not really. Raw fish contains lots of bacteria which can lead to food poisoning and even parasites. It also has certain enzymes which will destroy your cat's vitamin B levels. A lack of vitamin B can cause all kinds of health problems, including neurological issues and convulsions. The majority of cats suffering from a  B vitamin deficiency have been fed a diet high in raw fish, with the main culprits being cod, herring, carp, and pike. Again, it's important to reiterate that fish should be a small part of your cat's diet and that it should always be cooked before it’s being served.

Is there any fish that my cat shouldn't eat? 

Try and avoid tinned tuna or other canned fish. They have high levels of polyunsaturated fats and too much of this can lead to a common medical condition called pansteatitis. Also known as the yellow fat disease, pansteatitis is a physiological condition in which the body's fat stores become irritated and inflamed. The fat reserves then start to harden and stop helping the body metabolise food and energy sources. The symptoms of pansteatitis include rapid weight loss, depression, skin and coat problems, abdominal pain, and extreme sensitivity to touch.

Mercury poisoning

Some canned fish are very high in mercury, a naturally occurring element that is harmless in small doses. However, too much mercury can create a build-up of a  toxic substance called methylmercury. Exposure to high levels of mercury can harm the brain and other major organs. Other symptoms of mercury poisoning include:

  • Tremors
  • Weakness
  • Muscle atrophy
  • Twitching

Fish that are particularly high in mercury include marlin, swordfish, and shark. But more importantly for your cat, tinned tuna and mackerel have a very high mercury content. 

But don't worry if you've been feeding your cat small amounts of tinned mackerel or tuna. Again, the occasional fishy treat is fine; just make sure it stays occasional! 

The benefits of a little bit of fish 

Cats are obligate carnivores, which means they get most of their nutrition from high protein sources. Given that fish is high in protein, introducing a small amount into your cat’s diet is actually good for them. It gives them an important protein boost, but it also introduces a bit of variety into their diet. Cats are fussy eaters who can quickly get bored of eating the same foods every day. Plus, fish has high levels of omega-3 fatty acids. Your cat can't produce these naturally and so needs to get them from natural food sources. Omega 3 is important for brain and eye function. It also contributes to clear and healthy skin.

Fish is OK for your cat, but only in moderation. In fact, a small amount of cooked fish can actually improve your cat's overall health. Just stick to the 10% rule, and make sure the rest of your cat's diet is made up of high-quality pet food.  And remember: never feed them raw fish, and go extra easy on tinned fish!

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