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Can Fish Be Harmful to Cats?

Fish as a Part of a Cat’s Diet

Fish is not a natural part of a cat’s diet, and yet, due to the large variety of fish-based foods offered by pet food manufacturers, many cat parents believe they are providing an appropriate meal for their feline charges. While cats may enjoy the taste of fish, it is not always good for their health and can even be harmful in some cases.

A Look at Cats and Fish Through History

Cats and fish have had a long relationship that dates back to ancient Egypt, when fishermen took cats on boats with them to control rodent infestations. It is likely that fishermen would toss fish to the cats as a way to provide them with food.

While fish is not a natural prey for cats, there is one feline species that thrives on a diet of fish: the Asian Fishing Cat. Native to Southern Asia, these cats have partially webbed front toes and their claws protrude slightly even when retracted, which facilitates the capture of prey, especially while underwater.

Health Concerns with Fish and Cats

One of the main concerns with feeding cats fish is the mercury content in some fish. Mercury is a toxic metal that can accumulate in the body and cause damage to the nervous system, heart, and brain. Feeding cats fish with a high mercury content on a regular basis could potentially harm their health.

In addition, some cats may experience digestive issues when consuming large amounts of fish. Fish bones can also pose a choking hazard if a cat tries to swallow them whole.

While tempting to indulge your cat’s taste for fish, it is important to consider the potential health risks associated with feeding them a large amount of fish-based food. It is recommended to feed cats a balanced diet that includes a variety of proteins and nutrients to ensure their overall health and well-being.

The primary types of fish used in cat food are salmon, tuna, and tilefish (identified on labels as ocean whitefish). Each type of fish comes with its own set of issues.


Most salmon used in commercial cat food is farm-raised, rather than caught in the wild. These fish are kept in crowded pens and tanks in coastal fish farms. These waters are often polluted with PCB’s, pesticides, and other chemicals. To keep the fish healthy, they are often given antibiotics, and to make their meat look more like wild salmon, they may be dyed.


Tuna are predatory fish, which means they often accumulate high levels of heavy metals (including mercury) as well as PCB’s, pesticides, and other toxins from the smaller fish they eat. Mercury levels in tuna are such a big concern that the FDA recommends that people limit their intake of albacore tuna to only one serving per week. Additionally, tuna is very addictive to cats. If your cat is fed tuna on a regular basis, they may refuse to eat anything else.

Tilefish (Ocean Whitefish)

Tilefish, often labeled as ocean whitefish, are some of the most contaminated fish. They are so toxic that the FDA advises women of child-bearing age and young children to avoid eating them entirely.

How to safely feed fish

If you must feed your cat fish-based foods, it is best to limit their intake. Feeding them an occasional treat is acceptable, but too much can be harmful. If you choose to feed your cat commercial cat food containing fish, look for brands with low levels of heavy metals and other toxins. It is also important to rotate the type of fish your cat is fed to help balance out any negative effects from any one type of fish.