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Bite Compass
Pelagic / Offshore

Black Marlin

Istiompax indica

The 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.

Size
Up to 700kg+, commonly 30–150kg in WA
Peak season
Year-round in the north (best May–Oct off Ningaloo)
Minimum size (WA)
No minimum size
Bag limit (WA)
1 (tag-and-release is the standard practice)

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

Also known as 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

Best Baits

Rigged swimming gar or mullet, live yakkas, slimy mackerel or scad pitched to a raised fish, skip baits behind teasers

Lures

Skirted trolling lures (medium to large), Halco Laser Pro 190, large bibless minnows, switch-baiting with hookless teasers and a pitched bait

Rigs

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.

Technique

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.

Best Time

Juvenile black marlin are around the Ningaloo shelf year-round, and Recfishwest has them inshore in good numbers in the cooler months off Ningaloo — roughly May to October off Exmouth and Coral Bay. Broome and the Kimberley are more of a warmer-month proposition. Anglers rate run-out tides for concentrating bait along the drop-off; daylight is the window. Calm days with defined current lines make raising fish far easier.

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.

Last checked . Limits change — confirm with DPIRD before you fish.

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.

Where to Catch Black Marlin

Broome (Town Beach / Gantheaume Point / Roebuck Bay) Bundegi (Boat Ramp / Beach / Bundegi Reef) Coral Bay (South Ningaloo) Exmouth (North Ningaloo / North West Cape) Lighthouse Bay (Vlamingh Head Lighthouse / Surfers Beach / Limestone Platforms) Tantabiddi (Boat Ramp / Lagoon Gap / Outer Reef Drop-off)

Guides Featuring Black Marlin

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