Brachycentrus subnubilis - the Grannom

Phylum: Arthropoda - Class: Insecta - Order: Trichoptera - Family: Brachycentridae

In spring, the first sedge fly of real importance to river fishers is the Grannom, and it causes great excitement both on chalk streams and on rain-fed rivers. The Grannom appears in April and the main hatch usually lasts for ten days or so, with flies coming off the water from mid morning until late afternoon.

Trout tend to ignore small upwinged flies when the Grannom is on the water, but as other sedges are rare at that time a close imitation is probably unnecessary: any small sedge will do.

Fishing tips

This very popular and successful pattern was devised by Romsey flydresser Pat Russell, who fished with it extensively on the chalk streams of southern England. It is generally tied only on a size 14 hook.

On chalk streams, Grannom larvae are often to be found in greatest concentrations in and around weed beds, whereas on rocky spate rivers the swift, stony runs and glides are usually good places to fish during a Grannom hatch.

Although you may see lots of Grannom sedge flies in the air throughout the day, the main hatch (emergence from the water) often occurs in the morning, especially on southern rivers - sometimes as early as 10am - so morning fishing is often best.

References

O'Reilly, Pat. (1997; 8th reprint 2010) Matching the Hatch. Shrewsbury: Quiller Publishing.

Barnard, P & Ross, E. (2007) A Guide to the adult caddisflies or sedge flies (Trichoptera). Taunton: Field Studies Council.

Wallace, I. (2006) Simple Key to Caddis Larvae. Taunton: Field Studies Council.

Wallace, I.D., Wallace, B., & Philipson, G.M. (2003) Keys to the Case-bearing Caddis Larvae of Britain and Ireland. Ambleside: Freshwater Biological Association.

Macan, T.T. (1973) A Key to the Adults of the British Trichoptera. Ambleside: Freshwater Biological Association.