Don't feed fish to your cats and dogs!

Last November, I posted a warning about made-in-China chicken jerky treats that are killing our dogs. Now, here’s another word-of-caution.
If you love your cats and dogs, don’t feed them fish — excepting sardines and salmon — because they’re loaded with toxic metals like mercury. In this video, veterinarian Dr. Karen Becker explains why.

Here are the reasons for not feeding fish to our pets:

1. Many types of fish are contaminated with toxic metals like mercury, industrial chemicals like PCBs and dioxins, and pesticides like DDT.
These toxins are absorbed by the smallest ocean plants and animals at the low end of the food chain. As larger ocean dwellers come along and consume these contaminated plants and prey, the toxins accumulate and become more concentrated in the bodies of the bigger fish. This includes tuna, which many people regularly feed their cats and some dogs.
2. Pet food containing fish has a potentially deadly preservative, ethoxyquin.
The fish in pet food is heavily preserved during the manufacturing process using a chemical preservative called ethoxyquin, which is known to be a cancer-causing agent. Ethoxyquin is banned from use in human food except in very small quantities allowed as preservatives in spices.
Dr. Becker had experienced first-hand the heartache of ethoxyquin poisoning with her Rottweiler, Gemini. When Becker was in her sophomore year of vet school, 7-year-old Gemini went into liver failure after consuming food containing ethoxyquin. Becker got the food for free from a major pet food manufacturer who was giving away the stuff to vet students. It was then and there that Becker committed herself not to feed processed pet food ever again and began her quest for clean, healthy, pure foods in the pet food supply chain.
Unfortunately, ethoxyquin is still being used in many pet foods currently available on the market. It is used to preserve the fat in almost all fish meals – fat that is made from waste products.
If the label on the pet food doesn’t list exact ingredients, including the exact meat source, you have absolutely no idea what’s in that food. And because ethoxyquin is added before the raw ingredients are shipped to the pet food manufacturers, it doesn’t get listed or disclosed on the product label. In other words, the pet food company you purchase your cat’s or dog’s food from may not be adding ethoxyquin, but that doesn’t mean it isn’t in the fish meal in that food.
Don’t make the mistake of assuming if the fish meal product label doesn’t list ethoxyquin, it’s not in there. Unless the label specifically states the formula is ethoxyquin-free, or you call the manufacturer’s 1-800 number and are told it’s not in the raw materials they purchase nor added during their own manufacturing process, you should assume the formula contains ethoxyquin.
Fish meal also happens to be one of the main pet food ingredients also contaminated with mycotoxins.
3. Fish is not the natural food of cats.
While our cats seem to love seafood meals, fish was not the natural diet of cats’ ancient ancestors who came from the deserts of Africa. Cats’ natural prey are small furry land dwellers like mice. But even though the natural diet of cats isn’t seafood, they can get addicted to fish. In fact, kitties tend to become addicted to any protein they consume exclusively. Pet food companies are acutely aware of this phenomenon, which is why most cat food formulas are either fish or chicken based. These are the proteins cats most often form addictions to.
4. Fish is one of the most highly allergenic foods for cats.
We need to rotate proteins in our pet’s diet because any food that is over-consumed can create an allergy over time. Alas, it turns out fish is one of the most highly allergenic foods for felines. Allergies cause systemic inflammation. Cats that eat allergenic foods over and over can end up with lung inflammation that can also lead to asthma,  one of the more commonly diagnosed inflammatory conditions in cats. There also appears to be a link between asthma and two contaminants found in fish — mercury and ethoxyquin.
5. Other effects from long-term ingestion of fish

  • Fish fed in high amounts can also lead to thiamine deficiency, which can cause loss of appetite, seizures, and even death.
  • Long-term ingestion of fish in cat food can also deplete vitamin E resources. Vitamin E deficiency can also cause a really painful condition called steatitis, which is yellow fat disease. If left untreated, steatitis can also be life-threatening.
  • Seafood is a very rich source of iodine, but cats aren’t designed to process a lot of iodine. Many animal nutritionists, including me, believe there’s a link between cats consuming too many iodine-rich foods and hyperthyroidism. There’s also been a link established between pop-top cans or canned cat food and hyperthyroidism.
  • The magnesium content in fish has been linked to urinary tract diseases in cats because a diet overloaded with the mineral magnesium can predispose your kitty to magnesium ammonium phosphate crystals, also known as MAP crystals or struvite crystals. Crystals are a big problem for many, many cats.

Is There Any Safe Fish to Feed Pets?

Fish are a rich source of omega-3 fatty acids, which are essential to your pet’s well-being. You can supplement your pet’s diet with certain fish:

  • Sardines packed in water. Sardines don’t live long enough to store toxins in their bodies, and they’re a terrific source of omega-3s.
  • Wild caught salmon.

If you choose not to feed any fish to your pet, Dr. Becker recommends adding krill oil or another omega-3 fatty acid to their food.

H/t our beloved Joseph!

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lowtechgrannie lowtechgrannie

Good advice! Thanks for the tip


And for people who fish for salmon in the Pacific Northwest – look up salmon poisoning. It’s deadly.


Thank you Joseph and Dr. Eowyn for this most informative post. Sardines and wild-caught salmon are already on my shopping list!


Dang, if it’s like this, should we be eating it either?


Thanks for this information. I have two sweet cats and didin’t realize I was probably poisoning them. There are only two kinds of canned food they willl eat. Friskies, Chicken and Salmon and a couple of the the chicken ones. Theyeat Cat Naturals purina dry food too; but my vet says they need more than dry food. Can anyone give me some ideas what to feed my cats instead of these canned foods? I am sure that they are not good for them now. Maybe I should just cook them fresh chicken . They won’t eat beef or lamb. Let… Read more »

About Dogs and Cats

Very good source for education on pet care.


Excellent post. I will be dealing with some of these issues as well..


interesting email from the makers of Weruva and BFF. My 2 cats ate these 2 brands almost exclusively and mainly the fish flavors, the shrimp and rice, sardines, salmon etc. One developed hyperthyroidism and needed I-131 and it was a truly horrible year for her. My other cat developed IBD which set him up for gastric lymphoma. He is not on chemo and dying. After I began cooking all their meals, there was dramatic improvement in my female, hyper t cat but it was too late for my boy. These lines are poison. The dr is right about al of… Read more »


I meant my cat IS on chemo and dying. I knew it was the food so I started searching and found this article. I had taken all the flavors of the cans to two vets and asked if they were safe, one told me he sees obese cats who have never seen a can so I shouldn’t worry and the other told me it was too dangerous to cook myself as I am not a chemist. I never felt comfortable with these foods, I should have listened to my intuition. I then asked a 3rd vet and he told me… Read more »


weruva people are snakes and liars. their subpar cat food killed hundreds of cats this year in Australia.