The Colo forms where the Wolgan and Capertee rivers meet north of Lithgow and runs east through a deep gorge in Wollemi National Park to join the Hawkesbury. Two more rivers, the Wollangambe and Wollemi Creek, come in along the way and are its other main feeders. It sits almost entirely in rugged country, and the only road access is on the lower reaches.

Over its 86 kilometre course the river falls 214 metres, which is a gentle gradient for a gorge river. The gradient chart on this page shows the shape: a long, steady descent rather than a staircase, which is why the Colo is a river of long pools separated by short rapids and sand bars rather than pocket water. Bass sit at the heads and tails of those pools, along the shaded rock walls and under overhanging trees, and they move to the edges to feed at dusk and after rain.

The bank cover chart shows how much of the river runs through forest and sandstone rather than cleared land. That is the reason it fishes as it does: the water tends to run low and clear through summer, the fish are shy in bright light, and a rise after rain that colours the water is what brings them onto the feed.

Cox’s gudgeon and sea mullet are the two species recorded here, which tells you the lower river has an estuarine reach and that the small native gudgeon bass and everything else eat is present.

Australian bass are the fish. The river is described mainly as a summer bass fishery, so plan around the warm months. Bass here feed at dusk and dawn and after rain, take surface flies readily in the warm months, and hold in the deeper pools through the middle of the day.

Also present, according to the local fishing website, are eels, eel-tailed catfish, a few trout and some estuary species in the lower river, and Macquarie perch. The website names Macquarie perch as totally protected; that is a matter for the fishing department, so treat any Macquarie perch as a fish to release straight away and confirm its status in the current NSW rules before you go.

Cox’s gudgeon, a small native fish, and sea mullet are the species recorded here with high confidence. The gudgeon is the baitfish to copy: a small, dark streamer stripped along the bottom of a pool through the middle of the day is a gudgeon as far as a bass is concerned.

The surface forage in summer is terrestrial. Christmas beetles and grasshoppers fall from the trees and banks on hot days, and a bass that has heard a beetle land will move a long way to get it. That is why the surface fishing is a dusk and dawn affair on the shaded edges, and why a big dry or a popper worked along the trees is the fly of the season.

The Colo is mainly a summer fishery, and the local website’s advice on timing is specific: dusk and dawn, or just after heavy rain or during minor flooding. The calendar months follow from that, as a guide’s read.

From late spring through summer, fish the last hour of light and the first with a surface fly and the middle of the day with a streamer or a nymph in the deep pools. The hottest, brightest days are the ones when the dusk bite is strongest and the midday fishing is slowest.

A fresh after rain is the best fishing of the year. When the river rises a little and takes some colour the bass move onto the edges and feed hard, and that is the day to be on the water. A flood is a different thing. Never enter flood water; a gorge river in flood is not fishable and not safe to be near, and treat any creek crossing on a walk-in the same way.

Australian bass carry statewide seasonal rules, and the river is quiet in the cold months in any case. Read the current NSW fishing guide before you plan a trip outside summer.

Fish a six- or seven-weight with a floating line and a short, strong leader for the surface work. At dusk and after rain tie on a surface popper, a big hopper or a Christmas beetle pattern and work it along the shaded edges, under the overhanging trees and along the rock walls. Cast tight to cover, let the fly sit, twitch it, and let it sit again; a bass usually takes on the pause. Keep the rod low and strip-strike, then hold the fish away from the snags it will run for.

Through the middle of the day switch to streamer fishing in the deep pools. A weighted Woolly Bugger or a small dark gudgeon pattern on a sink-tip, counted down and stripped slowly along the bottom of the pool, will find fish that would never look up in bright light. A weighted nymph fished the same way is the other option the website names.

On the walk-in water, travel light: one rod, one small box with poppers, hoppers, beetles, a few streamers and a few nymphs, and a spare leader. Fish each pool from the tail up so you do not push fish ahead of you, and give the shaded side of the pool your first casts.

Bass are strong fish in a snaggy river, so fish a leader you trust and a net you can land them in. Support the fish in the water while you unhook it and let it swim off under its own power.

The access card on this page shows the ways in and the boat ramp on the lower river. Vehicle access is on the lower reaches off the Putty Road and nowhere else; the local fishing website names it as the only drive-in water on the river.

The walk-ins the website names are the Bob Turner Track, Canoe Creek and Wollemi Creek, all described as for experienced bushwalkers. Those are the website’s routes, not a statement that any of them is open to you; check the current national park track conditions and closures before you go. There is no mobile phone reception on those walk-ins, so carry a personal locator beacon, tell someone your plan and your return time, and pack for a night out even on a day trip.

Flood water is the hazard that will kill you here. The website’s own warning is never to enter flood water, and it applies to wading, to canoes and to vehicles at creek crossings. Treat any creek crossing on a walk-in the same way after rain. There is no gauge reading to lean on here, so read the forecast and the river yourself, and if it is rising, stay out.

Summer in the gorge is hot. Carry more water than you think you need, wear boots as you would on any gorge walk, and fish the edges of the day for your own sake as much as the fishing.

No water-specific rule was found for the Colo. Australian bass are covered by statewide NSW rules for size, bag and season, and those rules change; read the current NSW guide before you go.

A local fishing website names Macquarie perch in the river as totally protected. That is what the website states, and the fishing department is the authority; confirm it in the current NSW rules, and until you have, release any Macquarie perch immediately.

Before you fish, read the current NSW fishing rules and regulations, the freshwater bag and size limits and the general freshwater closures, and confirm the fishing fee.