A Guide to Caring for Bluefin Tuna after Spearing

It’s no secret that spearing a Southern Bluefin Tuna is no easy feat and requires preparation, time, hard work, technique and teamwork. Imagine after a long day on the water, spearing your trophy tuna, that you get home ready to cook up your fish only to discover it’s inedible and rotten. 

To stop this from happening, it’s important to understand and know the appropriate steps to take so you can dish up some fresh fish. 

Out of all the pelagic species, none require as much care as tuna - or in this case Southern Bluefin Tuna. In fact, Southern Bluefin Tuna can raise their body temperature the highest out of all tuna species - sitting at a hot 24-35°. It’s a tuna’s body heat that requires us to take care and properly cool down the fish so that the meat does not spoil. 

Below we’ve provided a step-by-step guide on how to properly care for your tuna.  Gear you’ll need to care for your tuna:

• 3 - 6 bags of ice 
• Boat hose - if available
• Spike / Ike or a small, sharp knife
• Monofilament or wire
• Large Esky or Fish Bag
• Thermometer
• To check out what we recommend when hunting Bluefin, visit our Spear Gear guide here. 

Step 1. Spike the Tuna

If this isn’t something you’ve already done in the water, the first thing you should do is spike the Tuna by inserting a thin metal spike or blade into its brain. 

Most tuna have a whiteish spot on their heads in-between their eyes, this is the best place to insert the spike. This kills the fish instantly and stops the majority of nerve activity or spasms. 

Step 2. Sever the Tuna’s Spine

In some cases, the fish’s muscle fibres will still cause unseen twitching along its spine - this can ruin the eating quality. 

Running a thin monofilament, or wire along the core of the tuna’s spine can reduce this risk and help all the muscles to relax. Typically you can run this from this by inserting the wire into the fish’s brain and pushing it through and along the spine to the tail. 

Step 3. Bleed the Tuna

The next step is to bleed the fish. This not only improves the flesh’s appearance but helps to cool the tuna’s core body temperature.  To bleed the fish insert and twist a small knife just behind its pectoral fins. Repeat this process on both sides. Only a small knife needs to be used, so you can preserve as much flesh as possible for eating. 

If you don’t get much blood from this process, then there are two other options to bleed the fish. This is to either rake the gill arc, by inserting the knife up and severing the membrane connecting the gills to the fish. And finally, the last option is to create a small lateral cut at the end of the tuna’s tail, which can help to further flush out any blood. 

Step 4. Gut / Gill the Tuna

To prepare your tuna for cooling, make a cut all the way around the gill membrane, severing all the gill attachments to the head. 

Next, make a cut along the anal opening, you should be able to fit your hand into there so you can dislodge the stomach and guts from the fish.

Be careful not to cut near the tuna’s belly - as this again could spoil the meat’s eating quality. You should be able to remove the tuna’s gills and guts, pulling them all through the gill cover in one piece.

From the gill cavity, give the fish a good wash out with a hose before you proceed to the next steps. This reduces the risk of the fish carrying any bacteria within the blood, loose tissue, or gill membrane that might spoil the fish. 

Step 5. Cool the Tuna

This is where it’s very important to ensure your boat is adequately equipped with all the supplies you’ll need to correctly chill your tuna. It’s best to have a large fish bag or esky to mix up ice and water, creating a nice slurry where you can completely submerge your fish. Make this a mixture of two parts water, to one part ice.

It’s handy to have a thermometer so that you can measure the temperature of the fish. Once the fish is cooler, pack it with all ice. 

If you do not have a fish bag or esky big enough, pack the gill and gut cavity with ice to try and bring down the core temperature of the fish. 

Step 6. Freezing your Tuna 

As bluefin tuna can be an especially large fish, we recommend cutting the fish into lions and sealing them individually in airtight bags so that you can store it properly in your freezer once at home. 

If you’re interested in learning more about targeting Southern Bluefin Tuna, check out our comprehensive species guide here.