River Blackfish
River blackfish are one of south-eastern Australia's most distinctive native freshwater fish — nocturnal, secretive, and tied tightly to clean upland streams.
They're a genuine target species in Victoria and Tasmania, where southern populations grow considerably larger than their Murray-Darling counterparts.
Catching one after dark in a forest creek is a different kind of fishing: slow, deliberate, and deeply satisfying.
Scientific Name: Gadopsis marmoratus
Also known as Slippery, Slimy, Muddy, Greasy, Blackfish, Nikki long cod
- Elongated body with rounded fins, a large head, and a rounded snout that slightly overhangs the wide mouth — unmistakable once you've seen one.
- Colour ranges from pale yellow-green or olive-brown through to near-black, usually with a dark marbled or blotchy pattern; belly is pale yellow, blue, or purple-grey.
- Pelvic fins reduced to a single branched ray positioned under the gill openings — a quick ID feature that separates this species from most other natives.
- Murray-Darling fish typically top out around 30 cm and under 0.8 kg; southern Victorian and coastal fish can reach 60 cm and over 5 kg in the best systems.
What to know
Habitat Distribution
- Endemic to south-eastern Australia — found from southern Queensland down through NSW and the ACT, widely across Victoria, into south-eastern South Australia, and across northern Tasmania (with introduced populations in some southern Tasmanian rivers).
- In the Murray-Darling Basin, mostly restricted to upper reaches and tributaries above 600–900 m elevation; more broadly distributed in south-flowing Victorian coastal rivers.
- Prefers clear, gently flowing streams with abundant in-stream cover — logs, snags, woody debris, and boulders. Rarely found over bare, open substrate.
- Distribution has contracted significantly due to siltation from agriculture and habitat degradation; many lowland and midland populations are now remnant or gone.
Key Locations
- Yarra River system (Victoria) — fishable blackfish habitat extends through forested and farmland reaches upstream of Yarra Glen, with good numbers in upper tributaries.
- Gellibrand River (Victoria, Otway Ranges) — a smaller, pristine system known for producing larger-than-average fish from its upper reaches.
- Upper Murray-Darling tributaries (NSW/ACT) — westerly-flowing upland streams above 600–900 m still hold populations where habitat remains intact.
- Northern Tasmania — rivers across the north of the state hold native populations; unsanctioned introductions have also established fish in the Derwent and Huon systems.
Specific Spots
- Dark, deep pools in small forest creeks — slower water with overhead cover concentrates fish, especially at night when they move out to feed.
- Submerged logs, root tangles, and large woody debris are core holding structure; fish tuck tight underneath and rarely stray far from cover during daylight.
- Rocky undercuts and boulder piles in upland streams provide both shelter and ambush points — work lures or bait right along the edge of the structure.
- Current breaks where fast water meets a deep, slow pool; fish hold in the calmer water and intercept food washing in from upstream.
River Blackfish FAQ
Answers from onWater's species guide.
What are the best lures and bait for River Blackfish?
Small soft-plastic grubs and curl-tail lures in natural colours (brown, olive, black) worked slowly along the bottom near structure are a consistent producer, especially at night.
What flies work for River Blackfish?
Small bead-head nymphs, Hare's Ear or Pheasant Tail patterns (which imitate mayfly and stonefly nymphs) dead-drifted near the bottom close to woody debris account for plenty of fish.
When is the best time to fish for River Blackfish?
Autumn and winter (March–August) are the most productive periods in Victoria, when fish are actively feeding and not subject to spawning-related closed seasons. Victoria imposes a closed season running through spring into early summer to protect spawning fish, check current VFA rules before fishing during this period.
How do you catch River Blackfish?
Most anglers target river blackfish after dark, working small lures or bait tight to submerged timber and rocky structure in forest creeks and upland rivers. Stealth matters, wading quietly and approaching pools from downstream reduces disturbance in the shallow, clear water these fish favour.
What do River Blackfish eat?
Crayfish and freshwater shrimp are a primary food source, soft-plastic lures in crawfish colours or small hard-bodied lures worked slowly along the bottom imitate this well.
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