The Grose rises near Mount Victoria and Bell and runs east through the Grose Valley inside Blue Mountains National Park to the Hawkesbury-Nepean near Agnes Banks. The gradient chart shows the drop: steep through the upper and middle valley, then flattening as the river leaves the gorge. The bank cover chart shows how much of the river is under forest, which is most of it.

The gradient chart marks almost all of it as a bedrock gorge, and in a gorge like this you can expect a chain of pools joined by runs and rock bars. In our experience bass are pool fish. Expect them to hold deep against rock walls, under timber that has come down off the slopes and in the shade of the overhanging bank through the day, then to move to the pool tails and the edges to feed as the light goes. Where the river leaves the gorge it slows and the bed turns sandier, and the fish sit on whatever structure the lower river offers, which is mostly snags and the shade of the bank.

Rain is what changes the river. A rise after rain is what moves the bass and, in a wet summer, pushes a few of them well up the valley. It is also the thing on this river that will hurt you: the website’s warning is never to enter a flooded river, and on any gorge stream a storm on the tops is your signal to be out.

Australian bass are the fish of the Grose, and mainly a summer fish. The river also holds eels, eel-tailed catfish, a few Macquarie perch and, in the upper river, a remnant population of trout. Cox’s gudgeon have been recorded here too, and a small gudgeon is the kind of thing a gorge bass eats between surface meals, which makes a dark streamer a good bet through the day.

Read the surface food as a guide’s judgement rather than a survey. In summer a bass river like this runs on what falls out of the trees: cicadas, beetles, moths and the odd hopper, most of it landing at dusk and after rain. The website that covers the river gives the same pattern for the Grose as for the Colo next door: large dries at dusk and after rain, streamers and nymphs through the middle of the day.

For a fly box that means two things. A handful of big foam or deer-hair dries, a Chernobyl Ant, a cicada pattern or a large Stimulator, for the low-light sessions. Then a few black or olive Woolly Buggers and a couple of heavy nymphs for the daylight hours. The trout in the upper river are a different trip and a different box; a small dry and a bead-head nymph will cover them.

Beyond the broad season, the timing below is a guide’s judgement built on what the river is known for.

The lower river bass fishing is often excellent in spring and early summer. A good bet for a first trip is October through December, on the water for the last hour of light and again at dawn.

Through the summer proper the fish are there and the pattern holds, but the day is long and hot in the gorge, so the fishing compresses into the two ends of it. A rise after rain is the exception; the day or two after a fresh can fish through the day.

In a wet summer bass push far up the valley, almost to the Govetts Creek junction, and a walk-in that would be a trout trip in a dry year can turn into a bass trip.

The remnant trout of the upper river are best in the cooler months. Whether any closure applies to the river in autumn and winter is a question for the current NSW guide.

Fish a six-weight with a floating line and a short, stout leader; bass are not leader-shy and the water is full of rock and timber. In the evening tie on a big dry, cast it tight to the rock wall or the overhanging shade, let it sit, twitch it once and let it sit again. Most takes come on the pause. The dry-fly presentation that matters here is not the drift but the patience.

Through the day switch to a black or olive Woolly Bugger and fish it slow and deep. Count it down along the rock walls and the timber, strip it in short pulls with long pauses, and expect the take on the drop. A heavy nymph fished the same way, dead slow, will pick up fish that will not chase; streamer fishing a gorge pool is about getting the fly to the fish, not the fish to the fly.

Move. A gorge pool gives up its fish quickly or not at all, so cover the likely water in each pool and walk to the next rather than beating one pool to death. After rain, fish the pool heads and the edges where the new water is bringing food down.

Barbless hooks and a landing net make releasing a bass simple, and every bass in a river like this is worth putting back.

No angler access site is listed for the Grose. What follows is how the local website’s writers reach the river; they are not a statement that any route is open to you, and the gorge is inside a national park, so check with NSW National Parks for track conditions and closures before you drive up.

The simplest entry is Yarramundi Bridge on the lower river, described as easy. The middle reaches are reached from Faulconbridge Point by a steep, rough route into the gorge. The upper river is reached by the bushwalking tracks that descend through Blue Gum Forest to the junction with Govetts Creek, and there are several of them.

Two things will hurt you here. The first is the gorge itself: a steep, rough route in and a climb back out, often in summer heat. Assume you will have no phone coverage in the gorge; start early, carry more water than you think you need and tell someone your plan. The second is flood. The website’s warning is never to enter a flooded river, and on any gorge stream a storm on the tops is your signal to be out. There is no gauge reading to lean on here, so read the forecast and look at the river before you go down.

No water-specific rule was found for the Grose. Australian bass in New South Wales are managed by statewide rules that may include size and bag limits and a seasonal closure in rivers; which of those apply on the Grose, and when, is a question for the fishing department.

The local fishing website describes the Macquarie perch in the river as totally protected. That is not the authority’s word, so read the current guide for the rule, and release any you hook without delay regardless.

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.