Yellowfin tuna are the benchmark of east coast offshore fishing. Fast, powerful, and unforgiving of gear weakness. An account of a two-day trip to the shelf break off Bermagui.
The Plan
The shelf break off Bermagui on the NSW South Coast sits about 35 nautical miles offshore, where the seafloor drops from a few hundred metres to over 2,000 metres in the space of a few kilometres. This abrupt depth change concentrates baitfish along the edge and draws the pelagic predators — yellowfin tuna, striped marlin, mahi-mahi, and wahoo — that follow them. In summer, when the East Australian Current pushes warm blue water close to the break, the fishing can be exceptional.
We were three anglers on a privately owned 7.5-metre centre console with twin 200hp outboards — capable of reaching the shelf comfortably in reasonable conditions and fast enough to run home if the weather changed. The forecast showed a two-day window between weather systems, which is about the best you get in summer on the South Coast. Success in this type of [offshore game fishing](https://wildrangelife.com/blog/offshore-game-fishing-port-stephens-marlin) depends on detailed weather analysis and proper timing. We left the harbour at 4am to reach the break at first light.
The Run Out
Two hours at 28 knots in the dark. The ocean outside the heads was a metre and a half with a 12-second interval — acceptable, if not comfortable. By the time the shelf change registered on the sounder and the water colour shifted from green to the deep blue of offshore water, the sun was just above the horizon and the conditions had laid down to near-flat.
The first sign of tuna was birds — gannets working a disturbance on the surface about two kilometres to the north. Gannets diving indicate baitfish being pushed up from below, which almost always means large predators underneath. We ran to them at speed, cutting the engines 300 metres out to avoid spooking the fish.
The First Strike
We rigged for casting — 6000-series spinning reels loaded with 50lb braid, 80lb fluorocarbon leader, and 60g knife jigs in chrome and blue. The bait school was visible from the surface — a dark, roiling mass of slender fish about the size of a hand being pushed up and decimated from below.
The first cast landed at the edge of the bait school and the jig had sunk perhaps three metres before the line went tight with a force that was not gentle. A yellowfin tuna in the 25-30kg range does not merely run — it accelerates with a sustained power that drains a reel at a speed you have to experience to believe. The first run took about 90 metres of line in under 10 seconds. The drag, set at 8kg of resistance, barely slowed it.
The fight lasted 22 minutes. The fish ran three times, sounded twice into water over 800 metres deep, and showed an endurance that was not declining when we finally got colour on it. A yellowfin of about 28kg, chrome-flanked and perfectly proportioned, alongside the boat. We gaffed it cleanly, brought it aboard, and killed it immediately.
The Day
We worked the shelf break for six hours that first day. The tuna school was present until around 10am, then dispersed as the sun rose high and the birds dispersed. In that window we boated four yellowfin between 18 and 32kg, lost three hookups to straightened hooks and one to a clean break of the leader at the boat — the result of a fish that turned back under the hull at boatside and got the leader over the transom corner.
The afternoon produced mahi-mahi on floating weed lines — three fish between two and four kilograms that hit surface poppers cast alongside floating kelp and timber. Mahi are different fish from tuna: faster to the surface, more acrobatic, easier to fight, and excellent eating. We kept all three.
The Second Day
Conditions deteriorated overnight. Two metres at nine seconds by dawn — workable but uncomfortable. We ran out anyway and found the shelf largely quiet. A single yellowfin school appeared mid-morning and produced two fish before disappearing. We were back in the harbour by 2pm ahead of the building swell.
Total across two days: six yellowfin tuna and three mahi-mahi. Approximately 100kg of fish. We kept what we could use and gave the remainder to other boats in the harbour who had not been out.
What It Requires
[Offshore fishing](https://wildrangelife.com/blog//blog/great-barrier-reef-fishing-gear-guide) at this scale requires a capable boat and an experienced operator who understands the weather, the mechanics, and the specific risks of offshore work on the NSW coast. The margin for equipment failure 35 miles offshore in a small boat is narrow. Everything needs to work reliably. EPIRB registered and activated, flares current, VHF radio operational, and a detailed float plan lodged with someone ashore are the non-negotiables before any offshore departure. This level of preparation is crucial when [planning remote fishing trips](https://wildrangelife.com/blog/how-to-plan-remote-fishing-trip-logistics) where you'll be far from assistance.
Understanding ocean conditions extends beyond weather forecasts to [reading tides](https://wildrangelife.com/blog/tidal-fishing-australia-how-to-read-tides) and current movements, which directly affect baitfish positioning and predator behaviour. UV protection for a full day on open water is essential. Browse our offshore fishing clothing range — long-sleeve UPF 50+ shirts, broad-brim hats, and polarised glasses for open water.
bait and immediately picked up a fish. The rod bent hard and line peeled off the reel in that characteristic tuna run — long, steady, and determined. The fight lasted twenty minutes on the spinning gear, with the fish making three substantial runs before coming to colour. A solid 15kg yellowfin, chrome-bright and built for speed. Landing that first fish confirmed what the bird activity had suggested — we were in the right place at the right time. The school moved off after the disturbance, but the GPS mark was locked in. Around the shelf break, tuna schools often return to productive areas within hours, following the baitfish movements and current lines that concentrate their food. For this style of fishing, your spinning gear needs to handle sustained pressure. The **Shimano Stella SW 6000** remains the benchmark for serious offshore work, though at $1,200+ it's not for everyone. The **Penn Slammer III 6500** at around $350 offers similar strength with a sealed body that handles salt water punishment [Check price on Amazon](AMAZON_LINK). Load either with quality braid — **PowerPro Spectra** or **Sufix 832** in 50-65lb test provides the casting distance and strengt enough for the 70-mile round trip and stable enough to handle the inevitable South Coast chop. We'd timed our departure for a 4am launch, giving us first light on the shelf break and maximum fishing time before afternoon winds picked up. ## Gear Selection for Deep Water Pelagics Targeting yellowfin in 2,000+ metres requires gear that can handle blistering runs and sustained pressure. We rigged four rods: two trolling setups with [Penn International 50VSW Reels](AMAZON_LINK) spooled with 80lb braid, and two casting rods with 6000-size spinning reels for when we marked schools. The trolling spread consisted of medium-size skirted lures in pink, blue, and black combinations. Yellowfin respond well to lures that mimic flying fish and small tuna — we had success with 6-8 inch models running 50-100 metres behind the boat. Wire leaders are essential; 80lb single-strand wire crimped to 9/0 circle hooks gave us the durability needed for multiple fish. For casting, we carried a selection of metal jigs from 80-150 grams. The [Shimano Coltsniper Jigs](AMAZON_LINK) in blue and silver proved deadly when schools surfaced. Having jigs ready meant we could capitalise on feeding frenzies that might last only minutes. ## Reading the Water and Finding Fish The continental shelf break creates a highway of nutrients and baitfish. We focused on areas where the sounder showed dramatic depth changes — from 300 metres to 800+ metres within a few hundred metres of travel. Temperature breaks were equally important; finding where cooler green water met the warm blue current often held concentrations of yellowtail and smaller tuna that attracted the larger predators. Bird activity remains one of the most reliable indicators. Gannets diving in tight formations, shearwaters wheeling and dipping, or the distinctive sight of frigate birds harassing other seabirds all signal feeding activity below. We'd motor towards any bird concentration and idle nearby while deploying the sounder to look for baitfish schools. ## The Fight and the Reward When a 30-40kg yellowfin takes off on its initial run, it's unlike any other fish. The reel screams for what feels like minutes as hundreds of metres of line disappear. These fish can sustain speeds of 60+ kilometres per hour, and their stamina is legendary. A proper yellowfin fight involves multiple long runs, often lasting 45 minutes to over an hour. The key is maintaining steady pressure without over-doing the drag. Set your drag at about 30% of your line's breaking strain and resist the urge to tighten it during the fight. [Quality fighting belts](AMAZON_LINK) and gimbal harnesses become essential for longer battles, distributing the load across your body rather than relying solely on arm strength. Once boated, yellowfin reward the effort with some of Australia's finest eating. The deep red flesh is perfect for sashimi when properly bled and iced, or can be seared rare for magnificent steaks. A single fish provides enough premium protein for multiple meals, making the offshore expedition worthwhile beyond the sporting aspect. ## Weather Windows and Safety Considerations South Coast conditions change rapidly, and being 35+ nautical miles offshore demands respect for weather forecasts. We always carried [EPIRB beacons](AMAZON_LINK), multiple VHF radios, and enough fuel for the return trip plus 30% extra. Morning starts are crucial — afternoon southerlies can create dangerous conditions for smaller boats on the return journey.