Where To Find Them

When To Find Them

What To Look For

Hatches of LBD's can be very localised, one river may be swarming with them - and another close by, be completely devoid of them.
The Large Brook Dun adult does not hatch through the water column (it climbs up stones and backside vegetation), so the emerger is not applicable to the fly angler.
Lifecycle
The life cycle of the Large Brook Dun is exactly the same as the Stonefly (below). There is usually a single generation per year, with the transformation from egg to Dun taking exactly a year.
Large Brook Dun nymphs are small, thin and can be found clinging to stones (one of the many 'stone clinging nymphs') and vegetation around the riverbed where the trout can pick them off, sometimes they get washed off their stones and the trout hoover them up. The best imitation for these is the famous Sawyers Pheasant Tail Nymph (beaded when used in heavier flows). When imitating the LBD nymph, please take note of the body thickness (most commercially bought flies have far too much material in the body), the body should be very thin. LBD nymphs are roughly 12 to 15mm long and only 3 or 4mm wide (just about the same as a size 14 Pheasant Tail Nymph):
Once the nymph decides the time is right to hatch into a Dun (usually around mid-day) the nymph climbs up a rock or bankside vegetation and transforms into the dun (as shown in the stunning photo below - Thanks Dave).
It takes a few moments for its wings to unfold and dry out (it is at this point where it is able to fly and find its mate).
Once mated, the female LBD flies upstream and descends to the surface of the water to release a few eggs by dipping the tip of her abdomen on to the surface at intervals, or by actually settling on the surface for a short period. After several visits to the water, her egg supply of up to 8000 eggs is finished and the spent female falls on to the surface, ready to be eaten by the waiting fish.
From a fly fishing perspective the stages which we must try to imitate are:
- Adult/Spent Females; and
- Nymphs
Imitations
Adult Females
March Brown Upright
March Brown Jingler
Nymphs


Image Sources
Large Brook Dun images: Courtesy of Dave Southall (thanks Dave, you're a star).
Flies
This email is brought to you with the sole intent to spread the information around so we can all maybe learn something. If you would like to buy any of the flies contained within this email, we do hope that you will consider us and see what flies we have to offer. If you would like any further details on any of the above flies, they can be found using these links:
Emerger:
March Brown Upright
March Brown Jingler
Nymphs:
Red-Neck Pheasant Tail Nymph
Pheasant Tail Mary
Previous issues of Hatch Chat can be found on our Hatch Chat blog, here: https://www.barbless-flies.co.uk/blogs/hatch-chat