Fish Vein or Worm

Fish Vein or Worm: How To Tell the Difference (Updated)

Last Updated on July 14, 2024 by Shari Mason

While enjoying your sushi and sashimi, you may come across something moving in the fish. It could be a normal fish vein or it might be a worm squirming in your salmon.

Here’s the thing. You’re possibly eating worms in your filleted fish, and you don’t realize it. But how to know if it’s just veins and not a worm?

Keep reading to know the difference and learn how to examine a fish to see if it has worms.

Comparing Fish Vein & Worm 

close up shot of raw fish fillet

Fish worms could be mistakenly seen as fish veins if you don’t know what it really looks like.

Fish veins are connected to every organ in the fish body, while worms are naturally occurring parasites found around open areas of the fish.

Also, fish veins aren’t coiled up and don’t move or wiggle inside the fish, unlike fish worms. 

Read: How Long Do Clams Live Out Of Water?

Main Difference


The veins could be visible in a fresh fish fillet, but it’s a worm if it starts to move. Veins in fish don’t move as worms do.


Fish worms are shorter than veins. A common worm found in fish could size roughly 2cm long when uncoiled, while veins are longer than in fish worms as it connects all the fish body parts.

Read: Can There Be Worms In Chicken Meat?


Fish veins might have a noticeable dark blue or purple appearance. Meanwhile, fish worms, like roundworms, are typically color red due to the presence of fish’s hemoglobin. [1]


Fish veins are connected to every organ and cell inside the fish body, while you might find fish worms mostly near the inside intestines of the fish.

“If you fish and catch nothing, you have still caught a lesson.”

– Matshona Dhliwayo, Author/Philosopher

How To Tell It’s Fish Worm or Vein 

Removing Worms from Fish

It Coils In The Flesh

Worm normally tends to coil themselves as part of their defense mechanism. On the other hand, veins are not naturally coiled and don’t have any coiled or twisted appearance. Find out how long cooked seafood can stay out here.

It Wiggles or Moves

If something is moving inside your fish, it’s a worm, not a vein. Fish veins don’t wiggle and can’t move from one place to another inside the fish.

It’s Near Open Surface

Fish worms are typically found mostly visible near open surfaces, like the belly of the fish, so they can get enough oxygen to live.

Will Fish Worms Get You Sick?

Yes. Fish worms can get you sick, particularly when you intake a worm in raw fish meat. 

In a worst-case scenario, eating infected fish could lead to severe abdominal pain resembling appendicitis that might lead to surgery. 

However, eating fish with worms will not make you sick when cooked. Worms in fish have no chance to live at high temperatures, and eating them cooked would cause nothing.

Read: Can You Eat Shrimp Shell?


Is it safe to eat fish with worms?

Yes, if it’s cooked, it’s safe to eat worms in fish. As the worms on fish are dead and have gone through the heat while cooking, nothing will happen if you eat one.

However, eating raw fish with worms could make you sick and lead to other health issues.

Do all fish have worms in them?

Almost all of the fish have worms in them. Finding a worm in fish is not a form of contamination. Most fish have naturally occurring worms like nematodes, also known as roundworms.

How do you inspect a fish for worms?

If you have a fillet from fish, you can carefully examine it by putting it over a transparent glass plate and running a flashlight underneath and check if there’s a worm.


When something unusual moves in your fish, check it twice; it’s a worm, not a vein. You can easily identify it by its movement, length, and color. Fish worms are shorter and is reddish, unlike fish veins.

In most cases, you don’t have to worry if you have eaten fish worms, especially when cooked. But if you experience abdominal pain or vomiting after eating a fish worm, you might want to see a doctor.


Shari Mason

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