The Grannom is a member of the Beraeidae family (Brachycentrus subnubilus) - consisting of around 30 distinct Caddis/Sedge species found throughout the UK, Europe and Russia. These Caddis flies are known as "humpless case-maker Caddis flies". These flies are easily identified in April as they will generally be the only Caddis fly on the water. The Grannom Caddis can be identified by its smokey grey coloured wings, which can have a slight yellowish tinge to them.

Please Note: You will often see these flies referred to as either Caddis or Sedge; they are both the same and are interchangeable as far as the fly angler is concerned.

Where To Find Them

Grannom can be found in every part of the British Isles. They can be especially prolific in Central, Southern and South West England; in Wales and Northern England (Ribble and Eden), and in parts of Scotland.

As with most Caddis flies, the Grannom is only found in running water. Grannom prefer gently running water, so you do not usually find them in very fast-flowing water.

When To Find Them

Grannom usually start hatching at the beginning of April and continue through until the end of the month.

What To Look For

Grannom are well known for their prolific hatches; just take a look at these photographs as a classic example (kindly supplied to us by David Southall, taken on an early afternoon on the river Tay):

Trout will take Grannom in any one of its three stages (nymph, emerger and dry). Grannom will generally hatch during the warmest part of the day (anytime between 11am and 3pm), so this is when to try an emerger pattern. Grannom usually hatch from shallower water and don't give the trout much of a chance to intercept them on their way to the surface. This is why fishing the emerger is your best bet, as the emerging Grannom is easy prey for a trout.

A favourite of the trout is to take the adult females, in the evening when returning to the water to deposit her eggs - time to give your Winged Grannom dry flies a try. The dry fly imitations you see for Grannom usually have a green tail section, as this represents the female's egg sack. 


Grannom Caddis nymphs start life as a cased nymph anchored to stones on the riverbed. Grannom nymphs build cases around themselves from vegetation found on the riverbed; you will often see them referred to as cased Caddis. These cases are roughly 12mm long and only 2 to 3mm wide (just about the same as a size 14 Pheasant Tail Nymph):

The nymph then pupates inside its case and exits the case to rise through the water column and emerge on the surface. This is the point that trout usually take them (either just below the surface or as they emerge), so don't be too quick to retrieve your fly if it should start to sink!

Female Grannom return to the water in an evening to lay their eggs, and this is when the trout take them as dry flies; rise forms can sometimes be very splashy and sometimes a generic "head and tail", but if you ever see Grannom in the air, then it's always worth tying on an imitation, especially in late evenings.

From a fly fishing perspective the stages which we must try to imitate are:

  • Adult Females
  • Emergers
  • Cased Nymphs


The most popular imitations for adult female Grannom are either of the dry flies below. Don't worry if you don't have these exact patterns, as anything which has the same general colour, profile and size will do. These flies should be fished as you would any other dry fly, and they should be used as soon as you start to see the females return to the water to lay their eggs; this can be anytime from about 18:00 until after dark.

Adult Females

Grannom Winged Dry


If you are fishing during the day, then nymphs are the way to go. Just make sure you are fishing near the bottom, remember: "if you're not getting snagged every now and then you're not fishing deep enough". Take a look at these for some inspiration:

Grannom Emerger



Grannom Caddis Pupa

Always keep in mind how deep and how fast the water is when nymphing in the early season, that will tell you how heavy a nymph you need to use. All you need to remember when fishing caddis nymphs in the early season is that you need to be very near (or on) the bottom, if you're not getting snagged up every so often, you're not fishing deep enough.

Image Sources

Header image, Cloud of Grannom & Grannom on Waders: Courtesy of David Southall

Caddis Lifecycle image: Courtesy of Cabelas (Dave Whitlock - Guide to Aquatic Trout Foods)

Cased Caddis Nymph: Courtesy of (Jan Hamrsky)


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:

Adult Female Dry Fly: Grannom Winged Dry

Emerger: Grannom Emerger

Nymph: Grannom Caddis Pupa

The next issue of Hatch Chat will cover the Large Dark Olive.