How to Bleed a Tuna

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If you’ve ever been out at sea tuna fishing with some experienced anglers or fishermen, you may have noticed them cutting some parts of the tuna and letting it bleed. This is a technique to keep the meat clean. Impress your fellow anglers on your next tuna fishing trip by learning how to bleed a tuna.

How to Bleed a Tuna

Fishermen generally bleed tuna to get rid of bacteria that may be present in the blood. It also helps cool down the tuna faster so it can last longer. Fishermen have different ways of bleeding their tuna while they’re tuna fishing.

Shimmering gray with black specks colored tuna being cut inside its head by a man holding a knife on a white boat

All of these methods produce the same result of bleeding the tuna. However, what method to use varies depending on the species or size of the tuna. Generally, people cut the gills of the tuna to make them bleed faster.

All you need for bleeding is a sharp knife and probably some bucket or mop to clean off the blood on your boat. The blood of tuna is generally not useful, so they are either spilled out at sea or collected for exotic tuna blood recipes.

Pectoral Cut

This cut is probably the easiest and best way to bleed tuna. All you have to do is make a small cut along the pectoral using a knife. Although be prepared to get messy as blood will spill out so fast.

Fishermen usually just let the blood flow in the boat and out at the salt water. If you find a use for tuna’s blood you can collect it in a bucket. Usually, anglers and fishermen just let it flow out. It will get messy so best to bleed out all your catch in one spot of the boat.

To do this cut:

  1. Lay the tuna on its side.
  2. Measure the width of two fingers from the base of the pectoral fin along the lateral line.
  3. With the same knife, make a clean cut through the lateral line of the tuna. The cut shouldn’t be too wide or too deep so you won’t damage the usable flesh.
  4. Flip the tuna onto the other side and repeat the same cut.

That’s how simple this cut is. That’s why most people prefer using this for tuna.

Gill Arch Cut

Another method for bleeding is by cutting the arch. The gill is like the throat of a fish so there are many blood veins there. Hence when it is cut, lots of blood will gush out. You can do the arch cut by following these steps:

  1. Lay the tuna on its side.
  2. Lift up the gill cover and cut the arch of the gill.
  3. Using a knife, insert it behind the gill. Run through the gill membrane.
  4. Afterward, cut up towards the spine. This will cut the blood vessel atop the gills and still leave the throat latch intact.
  5. Cut away the perimeter of the gill membrane.
  6. Check and make sure that you cut all of the attachments that keep the gills connected to the head of the tuna.
  7. Slowly remove the gills to start the bleeding.

That’s how you bleed the tuna using the gill cut method. It’s also a way to get rid of the gills right away after catch.

Combination Tail Sever and Gill Cut

This method is only applicable for very large tuna and is generally used by commercial fishermen. Some experienced anglers also do this and take out the innards of the tuna.

Shimmering grey with black specks tuna is being bled in a boat by a fisherman holding an orange knife

It is rarely done by anglers since the other methods are more simple and they catch only fairly large tuna.

To do this:

  1. Sever the two arteries located in the tail. It can be found near the anal fin of the tuna.
  2. Then, cut out the gills of the tuna, much like you do in the arch.
  3. Once done, hang the tuna by its tail so the blood flows down and drains out.

Hence why you often see tuna hanging by its tail when you see commercial tuna fishing boats or in tuna hunting on television. Sometimes, fishermen just cut the tail off, let it bleed, and store it in a cooler.

Generally, they just let the blood flow on the deck or have a bucket under the tuna to collect the blood. It’s the most optimal way to drain blood fast and reduce the weight of the tuna.

Reasons for Bleeding a Tuna

Bleeding a tuna has been a common practice all over the world. The Japanese refer to it as “Ikejime.” Most reasons for bleeding is for preserving the quality of the meat so it can sell for a higher price. Here are some other reasons why fishermen and anglers bleed tuna:

Eliminate Bacteria

The main reason most fishermen bleed the tuna is to get rid of various bacteria that the blood may contain. Some of these bacteria can be deadly to your health. Most fishermen also eat raw fish when they are tuna fishing, the need to bleed the tuna. 

Blood is also a great place for bacteria to multiply. Hence, it’s not advisable to leave blood inside your tuna or it could already be harboring bacteria or cultivating bacteria growth.

Cool the Tuna

Another reason why you should bleed your tuna is to help it cool. Blood is generally warm and a large tuna can contain gallons of it that will keep it warm for some time. When it is warm, the faster it will spoil.

Hence, bleeding helps cool down the tuna. In turn, the tuna won’t spoil faster. This is particularly useful if you don’t have a cooler and are planning for several days of tuna fishing.

Reduce the Buildup of Lactic Acid

If blood stays in the tuna, it could facilitate the build-up of lactic acid in the blood. Lactic acid builds up in the blood and muscles during strenuous exercise. This also applies to tuna.

When you catch a tuna, it’s gonna put up a fight which therefore makes it do some “strenuous exercise”. If you take a long time catching it, the muscles of the tuna could be stressed and tired and it will surely have a lot of lactic acid.

Red blood splattered across a newly bled tuna on a white fishing boat

Hence, that’s why you need to bleed it. Lactic acid can change the taste of the meat and also its texture into something unappealing. If you bleed the tuna, you reduce the chance of lactic acid buildup. You want to preserve the flavor and texture of tuna meat as much as possible.

Make it Look Appealing

A tuna will likely have discolored meat or dark spots in it. A bit of discoloration might not be that bad. However, it is important for commercial tuna fishing. Some buyers can call you out on the discoloration and ask for a lower price.

Easier Time Cleaning

If you plan to make use of the meat for the filet, then draining the blood will make your job easier. You don’t want blood spilling as you filet the fish. This will make your kitchen messy.

Blood is also slippery and sticky, which can be dangerous when handling a knife. Coagulated blood will produce more problems when you filet a tuna. Hence, the tuna should be drained of blood.

Reduce Weight

Weight is a frequent concern for commercial fishermen. A large tuna can contain several pounds of blood that can significantly add to the weight of the boat. This can mean less fish capacity.

This might also help recreational fishermen, especially if their boat is too small and needs all the available weight it can have.

Frequently Asked Questions

Do You Have to Bleed Tuna?

Bleeding the fish as quickly as possible helps make the flesh of the uncooked tuna look good. It also helps to get rid of bacteria and takes longer to spoil.

Where Do You Cut Tuna for Bleeding?

Tuna is usually cut near the pectoral fins, arch, and tail to bleed out. You can do a single part or a combination of parts.

Why Do They Cut the Tail Off Tuna?

The tail is the first part of chilling down. It is also the first part to be checked for grading, so they are cut and bleed first to make it the best-looking part.


Bleeding a tuna is a common practice when catching tuna. It has a lot of benefits, especially for keeping the meat of the tuna good and healthy. Bleeding the fish is an essential part of tuna fishing.