Many people are fascinated by snakes but turned off the idea of feeding them rodents.
One of the alternative foods that pet snakes can eat is fish—but only in small amounts, and only occasionally.
All pet snakes can eat fish.
The problem is that raw fish, especially decaying raw fish, can cause thiamine (vitamin B1) deficiency.
What’s Thiamine, and Why Is It Important to Snakes?
We all know that vitamins are vital to normal health. We don’t usually stop to think that snakes need vitamins, too.
Thiamine was the first B vitamin to be discovered, about a century ago. A snake’s body (and even a human’s body) can’t make it so it has to be obtained from food.
Thiamine is important for energy metabolism.
Because every cell in a snake’s body requires it, thiamine deficiency causes systemic symptoms, like confusion, malaise, and lack of energy.
But because snakes spend most of their lives quietly hiding, owners may not recognize symptoms of this vitamin deficiency before they are very advanced.
Many Fish Contain an Enzyme That Breaks Down Thiamine
OK, you may say, but what does this have to do with feeding my snake fish?
Many kinds of raw fish contain an enzyme that breaks down thiamine (which means that it can lead to a thiamine deficiency in your fish).
This enzyme, called thiaminase, becomes even more concentrated as fish decay.
People who consume fish sauce can develop thiamine deficiencies if they consume this concentrated form of uncooked fish.
People don’t develop thiamine deficiency, however, from eating sushi or sashimi.
In snakes, the effects of thiaminase are even more intense. Just eating one fresh raw fish can cause significant depletion of a snake’s thiamine.
Because thiaminase is also produced by the bacteria that live on decaying fish, feeding a snake a fish that has gone bad (or leaving a fish in your snake’s enclosure that it’s not immediately interested in eating) can make the problem worse.
A snake can compensate for the loss of thiamine with its next whole-animal meal, gaining thiamine from the kidneys and liver of the small mammals or birds it eats.
But regularly feeding your snake raw fish can provoke symptoms that are described as a snake’s version of the deadly disease beriberi.
Fish That You Should Never Feed Your Snake (in Raw form)
There are certain kinds of fish that always contain thiaminase.
You should never feed any of these kinds of fish to your snake without cooking the fish first.
- Atlantic menhaden
- Atlantic herring
- Baltic herring
- Broad-striped anchovy
- Brown bullhead
- California anchovy
- Channel catfish
- Common carp
- Chub mackerel / Pacific mackerel
- Gulf menhaden
- Lake whitefish
- Mediterranean mussel
- Rainbow smelt
- Round whitefish
- Ruby snapper
- Scaled sardine
- Skipjack tuna
- White bass
- Yellowfin tuna
Raw Fish That May Be OK to Feed Your Snake
Here is a list of fish that don’t contain thiaminase. They are safe to feed your snake if they are fresh.
But if they have begun to go bad, they also can generate the enzyme that in effect poisons your snake.
- Atlantic cod
- Atlantic hake / silver hake
- Atlantic halibut
- Atlantic mackerel
- Atlantic salmon
- Black crappie
- Black sea bass
- Brown trout
- Cisco/lake herring
- Coho salmon
- Hardhead catfish
- Lake trout
- Largemouth bass
- Lemon sole
- Northern pike
- Pond smelt
- Rainbow trout
- Redfish / Red perch / Rose fish
- Rock bass
- Silver seatrout
- Smallmouth bass
- Southern kingfish / King whiting
- Winter flounder
- Yellowtail flounder
- Yellow perch
- Yellow pike / Walleye
You should never give your snake any kind of fish that is native to tropical waters that has not been put on ice as soon as it is caught.
Barracuda and Tiger Fish can give snakes fatal infections with a different kind of bacteria that attacks the central nervous system.
Pet Snakes That Are More Tolerant of Fish than Other Snakes
There are three common kinds of pet snakes that are more tolerant of fish in their diets than other snakes: Garter Snakes, Ribbon Snakes, and Watersnakes.
These snakes eat a variety of aquatic organisms on a regular basis.
- Garter Snakes eat small rodents, worms, and small aquatic organisms like tadpoles, minnows, water bugs, and snails.
- Ribbon Snakes eat crickets, earthworms, mice, guppies, and tadpoles.
- Water Snakes eat insects, worms, rodents, small frogs, and small fish.
All of these snakes can tolerate fish, but they can’t tolerate every kind of fish.
It is especially important not to feed them goldfish, or fish that are closely related to goldfish, such as fathead minnows (the kind of minnow found in streams and ponds across the Eastern half of the United States) rosy reds, or tuffies.
Snakes should not be fed other “cyprinid” fish, such as carp or chub.
So, Does This Mean Fish Are Usually Bad for Snakes?
The problems from feeding fish to snakes arise when the fish are given to snakes raw.
Cooked fish don’t contain the thiaminase that can interfere with the B vitamin thiamine.
Cooking destroys other compounds in the fish that are beneficial to snakes, so it’s best not to give your snake any kind of cooked food on a regular basis.
Frequently Asked Questions About Feeding Fish to Snakes
Q. Is thiamine poisonous to snakes?
A. No. Thiamine is a vitamin. Thiamine is essential for snakes to survive. It’s the enzyme thiaminase (which is found in most fish) that breaks down thiamine. This can cause thiamine deficiency that is harmful to snakes.
Q. Would it kill my snake to give him a goldfish just once?
A. A single serving of raw fish, even if it contains thiaminase, is highly unlikely to kill your snake.
Thiamin (the vitamin) can deactivate thiaminase (the enzyme).
Your snake will get a dose of thiamine from its next feeding on a whole animal, including organ meat, especially liver and kidneys.
But because snakes digest food very slowly, it can take several days to several weeks for your snake to bounce back from the effects of eating even one goldfish.
Q. Would it be OK to give my snake wild-caught, organic fish?
A. No, wild-caught, natural ocean fish generate even more thiaminase than fish like tilapia and catfish that are raised in fish farms.
The higher the quality of the fish’s diet, the more thiaminase its body produces. Another problem with ocean-caught
Q. I just don’t want to feed my snake mice any more. I want to feed my snake, well, just about anything else. I have been offering my snake the “safe” fish on your list, but they don’t get eaten. What should I do?
A. Some snakes have strong preferences for a certain kind of food and just won’t eat until they are persuaded or forced to eat.
You may be able to persuade your snake to eat one of the kinds of fish that doesn’t contain thiaminase. Force-feeding your snake is something that has to be done by a vet.
To persuade your snake to try any kind of food it doesn’t usually eat, veterinarians recommend offering your snake food that has the scent of the kind of animal they usually prefer to eat.
If your snake normally eats birds, dip any food you want to feed them other than, say, chicken, in chicken broth so it has a bird scent.
You could also dip fish in chicken broth to give it a bird scent.
If you are weaning your snake off its frozen mice diet, you could try storing other foods in the package the mice were in to give it a scent with which your snake is familiar. Scents help snakes tolerate new foods.
Just be sure that you don’t overfeed your snake if it hasn’t eaten in a month or so. Snakes are vulnerable to a condition called an over-feeding syndrome.
When a snake gets a large meal of calorie-rich foods after a long period of fasting, its liver transforms excess amino acids from protein into sugar.
(Unlike humans, snakes make glucose from protein. Humans make most of their glucose from high-carb foods, which snakes don’t eat.)
The snake’s body moves excess glucose into cells along with potassium and phosphorus that ordinarily would be circulating in the bloodstream.
Low potassium and phosphorus levels can interfere with the snake’s nervous system so severely that it can die as a result of reseeding too much food too fast.
When you are trying to get your snake to eat a portion of new food, such as fish, start with small amounts.
You might feed a hognose snake just the amount of tuna fish you can put on your fingertip, for example. (Just don’t feed your snake your fingertip.) It’s better to feed a snake too little than too much, as long as you offer some food every day.
Fish is never the only food you should feed your snake, not even if you won a watersnake.
Be sure that you feed your snake cooked fish or raw fish from the “safe” list, and don’t make fish an everyday part of any snake’s diet.
Snakes thrive when they are fed a variety of familiar foods.
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