Fly Fishing Crai Reservoir: A Hidden Gem in the Brecon Beacons

Tucked away in a quiet corner of the Bannau Brycheiniog (Brecon Beacons National Park) Crai Reservoir is a truly special fishery — the kind of place that still feels wild, despite being relatively easy to access.

It’s green hued banks, clear waters, and a brooding landscape make this an ideal destination for the traditional fly angler in search of genuine Welsh wild brown trout.

While perhaps overshadowed by the more famous waters of the Usk reservoir or Talybont, Crai remains one of the Beacons’ best-kept secrets, offering solitude and a chance to connect with nature in its rawest form.

Crai Reservoir (Anglicised as Cray) lies to the north of the Western Black Mountain range, just a few miles from the village of Crai and just off the A4067. Although owned by Welsh Water, as a drinking water supply resource for Swansea, the reservoir is managed by the Cnewr Estate, who own the surrounding land and fishing rights.

A day ticket is available, currently at £15, using the honesty box located in the Cnewr Estate farm yard (what3words: ///machine.terribly.blink ). From there you’ll use an access gate just down the road, to a parking area just off the dam wall. You can then access the reservoir banks on foot.

Be prepared for a bit of a walk in places, especially if you want to reach the more remote western shores, which will involve dropping down below the dam, then following a rough path above the far bank.

Crai stretches to around 100 acres, with steeply shelving banks and depths of up to 28 metres near the dam, but also plenty of shallower margins perfect for the wading ‘cast and walk’ fly fisher. With a fair amount of shrub and stunted tree cover on the banks, it fishes best when the water level has dropped down a bit, otherwise you can fish in the many gaps along the tree dotted shore.

Wading is generally safe but can be tricky where the banks shelve steeply — wading boots fitted with studs are a wise choice.

Despite its size, Crai fishes like a small wild hill loch, and that’s exactly how you should approach it. It is not stocked — every trout here is wild, born and bred in the many feeder streams. As such, the fish are wily, stunningly marked, and incredibly quick on the take.

Don’t expect monsters – pretty free rising fish of 8 oz to 1lb are typical, with the odd surprise to 2lb. There have been tales of some very large fish caught here, but as always this is hard to substantiate.

Tactics and Fly Patterns

Crai’s trout are no pushovers. These aren’t stockies — you’ll need stealth, good presentation, and a dose of patience. Long leaders (think 18 foot in total) are often the key to success, especially on calm days. Usually fished as a team of two wet flies, on 6lb flourocarbon tippet.

A Bibio, Black Pennell, or Mallard & Claret fished with fairly fast strip retrieve can produce some surprisingly violent pulls. For the deeper drop-offs or when fish are sulking low in the many river-beds, a Black Tadpole or Humongous lure fished on an intermediate line can be a good searching method.

Dry fly fishing can be phenomenal when conditions allow on calmer overcast days. Keep your eyes peeled for rises to terrestrial insects coming off the hills, such as cow dung flies, hawthorns, bibio fly and beetles. Patterns such as Black hopper, Daddy long legs, Foam beetles or Black Klinkhammer’s can tempt fish that are patrolling the surface.

An important to is to keep mobile — don’t flog the same bit of water all day. Covering ground ‘walk and cast’ is often the best approach. Fan cast the water, including the shallow marginal edges. Look for points, bays, wind lanes or submerged structures, while keeping an eye out for insect activity and rising fish. Crai rewards observation.

Rod wise, bring something from 9 to 10 foot in length, rated from #5 to #7. The optimum rod would be a 10′ #6 weight in my opinion, a good balance between finesse and capability with the wind. A floating line, with an intermediate polyleader is a solid choice, bring an intermediate line along as well, for the sunnier and windier days.

Seasons and Conditions

The season runs from April 1st to September 30th on Crai, with the early months often being the most productive. As with many upland waters, the fishing is heavily weather-dependent.

A mild cloudy spring day, or overcast early summers day with a good ripple can bring phenomenal sport, while flat calm, hot days will often see the trout sulking in deeper water, only coming to life in the very late evenings. April, May and June are the prime months, then again come the end of September.

Fly fishing on Crai Reservoir is not about catching big numbers or big fish…. although on the right day you might well experience lots of action. It’s all about the challenge, the scenery, and the joy of connecting with truly wild fish in a Welsh landscape that still feels untouched.

Words: Ceri Thomas
Images: Alan Parfitt & Ceri Thomas