Southern Bluefin Tuna
This species guide has been written by Black Magic Pro Team member and Tuna Champions Scientific Ambassador, Jonah Yick. Jonah is an experienced angler who specialises in game and deep drop fishing, particularly off the east and south coasts of Tasmania (Australia). Jonah has worked in the fisheries field for over 15 years, on both freshwater and marine fish.
Some information in this article has been sourced from the following document: Tracey, S., Lyle, J. M., Stark, K., Gray, S., Moore, A., Twiname, S., & Wotherspoon, S. (2020). National Survey of Recreational Fishing for Southern Bluefin Tuna in Australia 2018/19
There are 3 types of bluefin tuna – Atlantic (the largest and most endangered), Pacific and Southern. Fish around 70-100kg or more are called jumbo or barrels. Fish in the 10-40kg range are called schoolies, in the 45-60kg range, they’re called kegs.
SIZE AND WEIGHT
They can grow to 160kg and over 2m in fork length. However, they are commonly caught in the 10 to 25kg size range, with the big fish ranging in size from 80 to 140kg.
Any fish over 120kg+ is an exceptional fish.
Officially, the largest SBT ever caught was 167.5kg, caught in Tathra on the South Coast of NSW, Australia in 2009. However, there was a large bluefin tuna caught recreationally from South Australia which was in excess of 170kg.
DESCRIPTION
Southern bluefin tuna are a sleek, impressively streamlined looking fish. All their fins slot into small grooves so they are essentially the perfect torpedo/bullet shape. Their back is jet black, with a turquoise blue shade down their side, transitioning to a silver belly. When looking at them in the water, their bright yellow finlets and yellow caudal keel are distinctive and eye catching.
Generally speaking, adult SBT have proportionally smaller eyes than adult big eye tuna and are less deep bodied/fat. Adult yellowfin tuna have distinctively longer second dorsal fins, while the second dorsal fins of SBT are relatively short. It's difficult to tell adult SBT apart from adult Pacific bluefin tuna, so genetic analysis is usually required.
Southern bluefin tuna, like other pelagic tuna species, can maintain their body core temperature up to 10°C (18°F) above the ambient temperature. This enables them to maintain high metabolic output for predation and migrating large distances.
The southern bluefin tuna is an opportunistic feeder, preying on a wide variety of fish, crustaceans, cephalopods and other marine animals.
WHEN AND WHERE TO FISH
Southern bluefin tuna are found in southern Hemisphere waters, mainly between 30°S and 50°S. Their only known breeding area is in the Indian Ocean, south-east of Java, Indonesia. Mature females (over the age of 8) can produce several million eggs in a single spawning season. Breeding takes place from September to April. Juveniles (aged between 1 – 4 years) then migrate south down the west coast of Australia and spend the winter in deeper, cooler oceanic waters.
SBT can be found pretty much anywhere oceanic, where their favourite schooling prey items congregate – generally redbait, mackerel, or squid. This is usually inshore over deep reef structures from as shallow as 10m to 150m deep.
SBT can also be caught over the continental shelf in depths from 150 to 600m. SBT usually use the shelf as more of a highway, and travel with the currents and associated bait abundances. As a result, they may not hold in particular areas for long periods of time.
In Tasmania, SBT are now almost a year round proposition, however traditionally the season is from March to June. Once again traditionally they were mainly targeted off the east and south coasts of Tasmania, both inside the continental shelf inshore as well as over. But these days SBT are also found on the west and north coasts of Tasmania. Big jumbo or barrel sized SBT are generally caught by trolling lures around offshore islands or reef structures. For some reason the larger fish are not often caught over the continental shelf by trolling, but instead are caught regularly as bycatch by anglers chasing swordfish dropping down baits to the seas floor. The SBT hot spots in Tasmania are the ports of St Helens and Eaglehawk Neck on the east coast, and the offshore islands Pedra Branca and the Maatsuyker Island group off the south coast.
The SBT fishery in Victoria and South Australia has also seen similar changes to their tuna season, where they can now be caught in almost every month of the year.
The peak period for bluefin in Victoria is generally from February to July, however this can extend through until October and November.
The tuna season in South Australia generally kicks off early in December and can also extend through until October/November. In South Australia, SBT can be caught all along the ocean coastline, from Ceduna in the west all the way through to the Victorian border in the east. The main ports where SBT fishing is undertaken are Port MacDonnell, Victor Harbour, and the Eyre Peninsula.
The SBT fishery around the Victorian border is very closely linked, where gamefishers will regularly travel from Victoria to fish in South Australia if the bite is on, and at times boats will launch from Victoria but travel across the border by water to reach the fish. Traditionally in Victoria, the fishery has mainly been focused on the western coastline, with the main ports and access points being Portland, Apollo Bay, and Port Fairy. However, in the last few years (as seen in Tasmania), big numbers of bluefin have continued to push further east and are now caught regularly around the entrances of Port Phillip Bay and Western Port Bay, in Bass Strait.
In NSW, the season for SBT is generally much shorter, and the fish are found much further offshore than the other states, typically many kilometres over the continental shelf. Anglers will routinely travel up to 100km offshore to reach the fishing grounds.
The mains areas to target SBT are along the southern half of the state, from Eden through to Newcastle. The season can range for a few weeks or a month, usually in June or July. Although the season is comparatively much shorter compared to other states, the average size of the tuna is much larger, making them worth the gamble to travel further!
The main technique to target SBT in NSW is to troll lures, however at times cubing can also be very effective.
The SBT fishery for Western Australia is also quite different to the other states, in that the fish targeted are small juveniles, which are migrating back from the spawning grounds in the Java Sea. The average size of fish caught are usually 5kg or under.
In New Zealand, SBT are most commonly found off the east coast of the North Island. The peak fishing season is between June and August, but they can also be found as early as March, and as late as September/October.
The bluefin run through Waihau Bay and along the East Cape of the North Island happens around June/July each year, and anglers will travel from all over New Zealand to try their luck on recreational boats or with the many charter companies that run in the area.
The larger pacific bluefin are also found in New Zealand off the west coast of the South Island.
HOW TO FISH
TROLLING
Trolling is by far the most common way to catch SBT. The best way to troll for tuna is with a spread of skirted lures, which can range from 6 to 15 inches long. Generally, you have five lure positions in which you stagger the distances of each lure behind the boat, so they don’t get tangled when you make tight turns and circles.
These positions in order of distance away from the boat are: short corner, long corner, short rigger, long rigger, shotgun.
Troll lures around structure which hold bait, in locations where SBT follow currents, or around bust-ups and surface activity which involves birds or marine predators.
Jonah fishes with our Flea XT, Maggot XT, Liquid lunch XT, and Jetsetter Maxi lures, which he rigs with 200lb Tough Trace and a 9/0 or 10/0 game hook. He sets up his overhead reels with braid backing and a mono topshot to increase his line capacity to the maximum. This is because big bluefin can take a 400m run at times. Either 50lb to 80b Rainbow Elite 8x Braid backing combined with the associated line class of IGFA monofilament (24kg or 37kg).
CASTING
Casting for bluefin is especially effective if they’re focused on small bait and are wary to take a trolled lure. Approach upwind of the bust up so you can turn the motors off and drift down onto them quietly.
The Ocean Born poppers and stick baits work very well for this, which Jonah rigs on 100lb Supple Trace with either 30lb or 50b Inferno Elite 8x Braid or Rainbow Elite 8x Braid.
Our Gladius® SW Spin rod is ideal for casting at school sized bluefin. Although light in action, it makes for a very sporting and fun fight, but you can still stay in control and dictate terms throughout the fight!
LIVE BAITS
Live baiting can be a deadly technique when the bluefin are being fussy and are not interested in taking a lure. Hook a small baitfish (redbait or mackerel) through the nose on a 6/0 or 9/0 LB Series hook. These are small hooks that allow the baitfish to swim, but are heavy gauge and very strong. They’re also carbon hooks so they can rust out if you plan to release the SBT and can’t remove the hook.
Rig the hook on 80lb – 130lb Tough Fluorocarbon which is hard to see in the water but very tough and abrasion resistant.
DEAD BAITS
Rig up a dead bait the same as you would a live bait. They can be cast into a bust up or simply floated down the water column if you can mark fish on your sounder.
Something which has evolved recently is catching big bluefin tuna as bycatch while targeting swordfish in 400m to 600m of water on the bottom. At times this can be quite a consistent technique. For this rig, Jonah uses 400lb Tough Trace, combined with a marlin live bait circle hook with a bridled bait, usually squid or a whole mackerel. He sets this up on an overhead game reel with Rainbow Elite 8x Braid and a 37kg IGFA monofilament top shot.
CUBING
This is similar to deadbaiting, but instead, you are berleying by chopping up small baitfish into cubes, but putting a hook in one of the cubes and sending it out through the water column. Jonah sets this up the same as he would for live or dead baits, and this style of fishing can be done either over the inshore reefs, or in deep water over the continental shelf.
JIGGING
When SBT are marking up on your sounder at depth, jigging can be an effective method for catching them. For example, if they are anywhere from 20 to 60m under the boat, dropping a jig down to them may get the bite.
Jonah uses 60lb to 100lb Supple Trace with our Knife Jigs for this style of fishing, matching the weight of the jig to the depth of the fish he is targeting. For example, 100gm jig or heavier for fishing 100m depth.
TIPS AND TRICKS
- If you plan to keep your fish, learn how to handle it correctly to maintain the quality of the meat. Little things like making sure everything the fish touches is wet with seawater (including your hands) can make a real difference
- Make sure you know how to dispatch, bleed, gill gut and cool your fish if you intend to keep it – find out more here
- If you intend to release your fish, limiting how much you touch the fish, or preferably keeping it boat side will reduce the amount of stress and damage to the fish, giving them the best chance of survival
- Tagging and releasing helps researchers gather useful data about SBT. There are tagging programmes available all over the world, so find out about your local programme if you’d like to contribute to this valuable research
- Using equipment like an Equalizer® gimbal and harness set can make all the difference when landing a big tuna. Our specially designed gimbal and harness set, allows you to apply maximum pressure to your fish without applying maximum pressure to your body.
- Learn how to reduce your fight time with bluefin tuna
- A brag mat is great for measuring fish quickly
TUNA CHAMPIONS
Tuna Champions is an initiative of the Australian Recreational Fishing Foundation in collaboration with the Institute for Marine and Aquatic Studies at the University of Tasmania. It is funded by the Australian Government and is focused on encouraging recreational anglers to fish responsibly and ethically for southern bluefin and yellowfin tuna and reducing wastage. The SBT population is still recovering, but with continued careful management and good recreational fishing practices. the fishery will continue to improve in the coming years.
SBT are fantastic eating fish so look after the meat carefully, but if you don’t want to eat them, consider tagging and releasing them. They have a great post-release survival rate if handled correctly and carefully.
Check out the Tuna Champions website for more great information and tips.
GEAR GUIDE
EQUALIZER® GIMBAL AND HARNESS
Using equipment like an Equalizer® gimbal and harness set can make all the difference when landing a big tuna. Our specially designed gimbal and harness set, allows you to apply maximum pressure to your fish without applying maximum pressure to your body.
