Black Marlin
Pelagic / OffshoreThe heavyweight billfish of WA's tropical north and the headline gamefish target out of Exmouth and Broome. Black marlin range the bluewater along the continental shelf from the Gascoyne through the Pilbara and Kimberley, with juvenile fish accessible to small boats and giants taken offshore. Tag-and-release is the universal ethic — these are a trophy to raise, fight and let go, not a fish for the esky.
Overview
Black marlin are the apex gamefish of WA's tropical coast — fast, powerful, and capable of spectacular greyhounding leaps that define a season for the anglers who tangle with them. The continental shelf runs close to the coast at Exmouth, putting billfish water within reach of Tantabiddi boat ramp, while Broome and the wider Kimberley produce fish over the warmer months. WA waters hold everything from accessible 'rats' of 20–40kg up to genuine grander-class fish offshore. Black marlin are raised on bait schools and current lines along the shelf edge, and the Exmouth and Broome game fishing clubs run active tag-and-release programmes — the overwhelming majority of fish are tagged and released to fight again.
Identification
Blacks, silver marlin, 'rats' (small fish)
The one diagnostic mark is the pectoral fins: on a black marlin they are rigid and cannot be folded flat against the body, even on a dead fish. Everything else follows from that check. Blue marlin have flexible pectorals, a pointed front dorsal roughly as tall as the body is deep, and cobalt bars; striped marlin are slimmer with a tall dorsal and obvious pale stripes; sailfish carry the unmistakable sail. Black marlin are the heaviest-bodied of the group, with a lower, round-tipped dorsal and a shorter, thicker bill. Small fish are 'rats' in gamefishing shorthand.
How to Catch
Rigged swimming gar or mullet, live yakkas, slimy mackerel or scad pitched to a raised fish, skip baits behind teasers
Skirted trolling lures (medium to large), Halco Laser Pro 190, large bibless minnows, switch-baiting with hookless teasers and a pitched bait
Gamefishing tackle — 15–37kg overhead or heavy stand-up spin, 130–400lb mono or fluorocarbon leader, 8/0–10/0 circle hook for bait (mandatory under most tagging programmes). Run teasers to raise fish, then pitch a circle-hook bait or stickbait. Quality ball-bearing swivels and a sound drag setting are essential — the first run is brutal.
Troll skirted lures and rigged baits at 6–9 knots along the shelf edge, current lines and bait schools, watching for tailing fish, free-jumpers and working birds. When a marlin lights up in the spread, drop a bait back or pitch a live bait and let the fish turn before loading the circle hook with a steady lift — don't strike. Clear the deck on hook-up and let the fish run; black marlin jump early and often. Release boat-side without lifting the fish from the water, leadering and tagging alongside the boat.
October through April is the productive window in northern WA, with summer into early autumn the most consistent at Exmouth and Broome. Some fish are around the shelf year-round. Run-out tides concentrate bait along the drop-off; mornings and the change of light tend to fire best. Calm days with defined current lines make raising fish far easier.
Up to 700kg+, commonly 30–150kg in WA
Oct–Apr (Exmouth/Broome summer–autumn)
Size & Growth
Exmouth and Broome produce everything from rat blacks of 20–40 kg, which small boats can handle on lighter gear, up through the 80–150 kg fish that make up most of the tagged captures. Genuine giants of several hundred kilos exist along the shelf and are occasionally raised, but they are not the everyday fish. Females grow far larger than males, so any very big black marlin is a female. They grow quickly in their early years, which is what makes the juvenile fishery so accessible, and that same growth is why releasing a rat is worth far more than boating one.
Diet & Habitat
Black marlin hunt schooling baitfish and small tuna — mackerel scad, bonito, mackerel, squid — usually high in the water column along the edges where blue water meets structure or current. In WA the continental shelf swings unusually close inshore at Exmouth, which puts billfish water within half an hour of Tantabiddi ramp and makes the fishery reachable by trailer boat. Broome, the Kimberley and the Gascoyne shelf produce fish over the warmer months. Look for bait schools, temperature and colour changes, working birds and free-jumping fish along the drop-off rather than trolling empty blue water.
WA Size & Bag Limits
| Minimum size | No minimum size |
|---|---|
| Bag limit | 1 (tag-and-release is the standard practice) |
| Counts toward | Counts within the statewide mixed daily bag limit of 3 for large pelagic finfish. |
Billfish (marlins, sailfish and spearfish, Family Istiophoridae) sit within the statewide mixed daily bag limit of 3 for large pelagic finfish, with an individual species daily bag limit of 1. No minimum size applies. In practice, tag-and-release is the recreational and tournament standard for black marlin in WA and retention is strongly discouraged — the game fishing clubs at Exmouth and Broome run tagging programmes.
Eating Quality
Black marlin are not an eating fish in WA, and there is no good reason to make one. The recreational and tournament standard is tag-and-release, the fish are worth vastly more alive to a fishery that runs on repeat captures, and the flesh itself is unremarkable — dark, coarse and strongly flavoured, nothing like the tuna it swims with. Large tropical billfish also carry a ciguatera risk, and as a long-lived apex predator marlin accumulate mercury, putting them among the species Australian food-safety advice says to limit sharply. The right outcome for a black marlin is a tag, a photo taken with the fish still in the water, and a clean release beside the boat. Retention is legal within the bag limit, but almost nobody does it and the clubs actively discourage it.
Perth Tips
Tantabiddi boat ramp at Exmouth puts you within thirty minutes of marlin water — exceptional access for a billfish fishery. Broome and the Kimberley produce fish over the wet-season build-up. Use circle hooks, fish single-strand fluorocarbon leader, and have a tag pole, gloves and a plan for a clean boat-side release before you ever raise a fish. Don't lift a marlin out of the water for photos — keep it in or beside the boat, revive it, and let it swim off strong.