Fly Fishing Devon: Instruction & Guiding on Dartmoor Rivers

Natural and Artificial Trout Flies of the River Yealm

The Yealm is a relatively short (12 miles long) river representative of several rivers running off the southern slopes of the Dartmoor National Park in South Devon (UK).
It carries a good head of brown trout, a run of sea trout in summer months and salmon in the autumn (November and December).

In 2011 the environmental consultancy firm APEMcarried out invertebrate surveys at seven sites using the kick sampling procedure.

Samples were collected on 25/26th May, 2011 (Spring Survey), 19 August 2011(Summer Survey), and during the week of the 19-23rd September 2011(Autumn Survey).

This page summarizes the survey results and lists the most frequently found insects. It may be of interest to fly fishers visiting the Upper Yealm Fishery and other similar rivers in South Devon.

The survey sites were very similar to these images of the Upper Yealm Fishery beat. The main flow types were run and riffle, with sand and pebbles/gravels dominating the substrate. The wide variety of river flies found in the River Yealm is typical of clean, fast flowing, stony rivers.

NOTE: The scientific names for insects are shown in italicson this page. The associated link opens a new window / tabbed page showing the results of a Google search for images of that particular insect. Anglers names for insects are shown in normal typeface and the associated link also opens a new window / tabbed page showing the results of a Google search for images of the range of fly patterns used by anglers to represent that particular insect.

Invertebrate survey results: Spring 2011

Invertebrate survey results: Summer 2011


Beetles were abundant.
But many of the species noted in the spring survey were either much reduced in abundance or absent.
  • Abundances of Olives (Baetidae) especially Large Dark Olive (B. rhodani), Olive Upright (R.semicolorata,and Blue Winged Olive (S. ignitus) and Stoneflies (L. geniculata) and Blue Winged Olive (S. ignitus)were much reduced in summer, or were absent - Small Yellow Sally(S. torrentium)- perhaps reflecting the less energetic flow environment present during the summer months
  • Beetles( Elmidae) abundance was increased in summer
  • Freshwater Shrimp (Gammurus pulex) abundances were much reduced in summer
  • a stonefly species of the highest conservation value Early Brown( Protonemouri meyeri) could be considered common on the Yealm

Invertebrate survey results: Autumn 2011


Food for thought?

  1. Finding beetles in the summer kick samples highlights the importance of considering terrestrial insects as a source of trout food that can be imitated by the angler
  2. The results show that midges (chironomids) are an abumdant source of food throughout the year. There is increasing awareness of the impotance of these insects to fly fishers which is reflected by several recent excellent books and videos on this subject listed in the Further Reading section below.

Further reading/viewing

  1. Aquatic Ecology Surveys of the River Yealm, 2011.
    FINAL REPORT December 2011APEM REF: SLR 411662.
    APEM Ltd. Aquatic Ecology laboratories
    FBA East Stoke
    Wareham
    Dorset,
    BH20 6BB
    Tel: 01929 405430
    Website: www.apemltd.co.uk
  2. Ed Engle's bookson tying and fishing small flies including midges (chironomids)
  3. Mike Lawson's video on midge fishing
  4. There is much food for thought in this (long) YouTube videothat highlights the importance of terrestrials as trout food; there are tying instructions after the fishing section
  5. "Small but perfectly formed": Some lesser-known westcountry river flies. This page explores some of the lesser-known species of insects which can be found if you examine the stones in the rivers of Dartmoor and South Devon.

Fly tying videos

  1. Tying the Black midge/gnat
  2. Craig Matthews shows how to tie the Improved Baetis Sparkle Dun
  3. Craig Matthews shows how to tie the X-Caddis
  4. Davie McPhail tying the Cruncher
  5. Detailed instructions for tying Craig Mathews's Zelon Midge