A Guide to Feeding Cats Fish Safely and Beneficially for Their Health

1. Do Cats Eat Fish?

Cats undeniably have a strong affinity for fish. The mere smell of fish instantly drives them “crazy” with excitement. But is it safe for cats to eat fish? Let’s find out!

a. Can Cats Eat Fish?

The ancestors of cats did not consume fish. They lived in deserts and forests, relying on mice, rabbits, birds, and lizards for survival. Therefore, from an evolutionary perspective, fish are not part of a cat’s nutritional needs. However, domestic cats today go wild for fish and can consume it day after day without getting bored. There’s no denying that fish is packed with nutrients, but it also comes with potential downsides.

i. Benefits

Fish such as tuna, salmon, anchovies, sardines, mackerel, and trout are rich in nutrients. They provide high-quality protein with essential amino acids and taurine, as well as fats, omega-3 fatty acids, carbs, calcium, potassium, phosphorus, magnesium, iron, zinc, copper, selenium, vitamins B and E, iodine, phosphorus, and other vitamins and minerals.

ii. Drawbacks

Fish contains a high amount of histamine. But what is histamine? Histamine is a compound produced by white blood cells to prevent infection and inflammation. However, it can also cause allergic reactions such as nasal congestion and watery eyes.

Different individuals, including cats, react differently to histamine. Therefore, consuming fish high in histamine can trigger allergic reactions. In fact, after beef and dairy, fish is the third most common cause of protein allergies in cats.

Food allergies can lead to digestive disorders and skin problems, including itching, hair loss, and secondary infections. Allergic cats may exhibit symptoms such as diarrhea, vomiting, and digestive disorders.


– Contain Toxins

Fish living in rivers and oceans are often contaminated, and there is evidence that they may be exposed to serious pollutants in the water.

  • PCBs and preservatives are major concerns not only for cats but also for humans. These substances can cause skin problems, organ failure, and even cancer. Farmed fish have higher PCB levels than naturally caught fish, mainly due to their fishmeal-based diet.

  • Harmful pollutants such as Polybrominated Diphenyl Ethers (PBDEs) increase the risk of hyperthyroidism in cats.

  • Fish can be contaminated with heavy metals such as mercury and magnesium. When cats consume excessive amounts of fish, it negatively affects their lungs, kidneys, and brains. Meat-eating fish such as salmon, swordfish, and tuna are more likely to contain higher levels of mercury.

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  • Impact on Kidneys and Urinary Tract

According to Darwin’s Pets, cats that eat fish with bones, guts, or parts that humans do not consume have high levels of phosphorus and magnesium. This can cause problems for cats, especially those with urinary or kidney issues. In some cases, sensitive cats may experience bladder inflammation and even urinary blockage if they eat any type of fish.

To answer the question “Can cats eat fish?” – Yes! You can feed cats fish, but it must be done correctly.

2. How to Feed Cats Fish

a. Fish Should Only Make up a Small Portion of Their Diet

Fish is not an appropriate source of nutrition for cats. Meat is the main and essential food for cats, as it contains the necessary nutrients for their well-being. I recommend reading the guide on “What to Feed Cats” to ensure your furry friend eats appropriately.

In nature, cats do not commonly consume fish. Therefore, their development does not heavily rely on fish as a main food source. If you feed cats fish as the main course, they may end up consuming more ethoxyquin, mercury, and PCBs than usual.


Fish is abundant in beneficial Omega-3 and Omega-6 fatty acids for heart health. However, it does not provide sufficient amounts of other essential minerals for cats, such as calcium, sodium, and iron. It also contains excessive phosphorus levels. Therefore, feeding cats excessive amounts of fish is not beneficial for their growth and health.

Furthermore, fish is high in magnesium and iodine. Cats do not require a large amount of iodine, and some veterinary scientists believe it may contribute to the development of hyperthyroidism. High amounts of magnesium can lead to the formation of struvite crystals in a cat’s urine. This can result in urinary tract diseases and emergency urinary obstruction in male cats.

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Hence, it is advisable to feed cats fish only a few times a week and ensure that fish accounts for no more than 10% of their total food intake.

b. Remove Fish Bones

Can cats eat fish bones? Is it safe to feed them whole fish with bones? It is strictly forbidden to feed cats fish with bones. Bones can damage or block the throat and gastrointestinal tract of cats. This can lead to blockages and internal bleeding. Even if you have removed the bones from the fish, small bones may still cause harm to your cat. It is important to carefully remove all bones to ensure your cat does not consume them.

c. Do Not Feed Cats Raw Fish

Can cats eat raw fish? Raw fish contains an enzyme called thiaminase that breaks down vitamin B1 (thiamine). Thiamine deficiency can cause cats to lose their appetite, experience vestibular disorders, seizures, aggression, and even death. Most cats diagnosed with thiamine deficiency have consumed significant amounts of raw fish such as carp, catfish, snowfish, tilapia, and other types of fish.

Thiamine can also be destroyed by heat, but it is usually added to cat food after processing to ensure cats do not suffer from thiamine deficiency. Additionally, feeding cats raw fish is a common reason for parasitic infections and allergies. This can result in diarrhea, vomiting, and other gastrointestinal issues in cats.

d. Avoid Oil-Soaked Fish

Oil-soaked fish (such as canned fish) contains a large amount of unhealthy saturated fats. This can cause common joint inflammation in cats. Symptoms may include loss of appetite, depression, poor coat condition, hypersensitivity, abdominal pain, and even death.

However, feeding cats fish oil is beneficial. Fish oil is commonly found in supplements and helps reduce intestinal inflammation, slow tumor growth, and prevent infections.


3. What Fish Should Cats Eat?

a. Fish Cats Should Eat

  • Fatty Fish: Provides cats with healthy fats such as Omega-3 and Omega-6. These fats are beneficial for a cat’s heart and even their vision. Fish oil is also ideal for older cats and can help alleviate some pain if they have inflammation. However, fatty fish can contain high levels of mercury. Feeding cats excessive amounts can lead to mercury poisoning.
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Below are some types of fatty fish that cats can eat:

  • Tuna

  • Salmon

  • Anchovies

  • Sardines

  • Mackerel

  • Trout

  • Other Types of Fish: Although non-fatty fish do not provide the same healthy fats and fish oil, they are still safe for cats:

  • Tilapia

  • Snowfish

  • Hake

  • Catfish

  • Carp

  • Catfish

b. Fish Cats Should Not Eat

  • Tuna: Do not be surprised to find tuna on both the safe and unsafe fish lists for cats. While it is good for cats, tuna contains more mercury than other types of fish. Additionally, it contains high amounts of fat and very little vitamin E, which can make cats extremely fond of it. Some cats may even refuse anything other than tuna once they are accustomed to its taste. This can be a dangerous dietary habit for any cat. Vitamin E deficiency can cause a severe and painful condition called yellow fat disease, where fat tissues become inflamed.

  • Tilapia: It tends to be heavily contaminated with lead.


  • Dried Fish: Usually contains a high amount of salt and is not good for cats, especially those with kidney or urinary tract issues. If not salted, fish is often preserved with additives to extend its shelf life. Therefore, it is best to avoid feeding cats dried fish.

  • Canned Fish: Many canned cat foods have a “fish” flavor, but they often include a variety of fish and by-products such as bones and scales. If you choose to feed cats canned fish, opt for single-ingredient products.

Canned fish is processed and treated with various spices and ingredients. They are often soaked in oil (olive oil, sunflower oil, soybean oil, etc.). Therefore, it is best not to feed cats canned fish.


Can cats eat fish? Can you feed cats fish? As long as cats are not allergic to fish and the fish constitutes only a small portion of their well-balanced diet, you can safely feed cats fish. Fish is a rich source of protein. However, be cautious of creating a fish addiction in cats, as they may refuse to eat other types of food. Therefore, avoid introducing excessive amounts of fish into their diet from the beginning. If your cat predominantly eats fish, you may need to gradually incorporate non-fish foods and reduce the amount of fish.

Remember to always prioritize the well-being of your feline friend and ensure a balanced, nutritious diet.

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