Spate · Peat · Outer Hebrides / Lewis, GB-SCT

Grimersta River & Loch System

Grimersta River - geograph.org.uk - 2639590

Scotland's most famous island salmon fishery — a short, fast spate river draining a chain of lochs on the west side of Lewis.

Today · Closed season
Claret Bumble
Forecast · Today
Closed season
Out of season. File this water for the right month.
40% projected
Today's fly
Claret Bumble
Claret Bumble
Conditions on the water · Today
Proxy gauge
Level
Rising
Proxy
via River Ewe / Loch Maree
Water temp7.9°C
ClarityUnfishable
Weather7°C
WindN 42 km/h
Pressure1000 hPa
Rain · recent5.7 mm
Rain · ahead3.4 mm

No gauge on this water — conditions are inferred from River Ewe / Loch Maree. The trend transfers, the absolute level does not.

Water temperature for Atlantic Salmon
Cool — slow
8°C est.ideal 10–16°C
0°14°28°
How to fish it · for Atlantic Salmon
When
All day — lough fishing is best in a good wave. Early morning and evening can produce in calm conditions.
Where
Work the drift lanes from the upwind shore across the productive zones. Cover bay edges, underwater reefs, and any areas where the bottom shoals.
Method
Fish a sensible line-and-fly combination for the height and pace of water.
Kit
10 ft #7/8 single-hander, floating line, 10–12 lb fluoro leader. Boat seat and waterproofs for the drift.
Likely species
Stoneflies
Chironomids
Hatch timeline · todayPeak at 10am

12pm(now) — Black Midge

Stage: On emergersApproach: Emerger or dryActivity: 22%

Peak activity at 10am — Black Midge

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 4 guilds as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Supporters see what else is on the menu.

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Evidence
Survey-backed · regionalHigh confidence

Backed by regional invertebrate surveys; no sampling on this exact reach yet.

Through the year
0–3 scale · November highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Salmon runRun
1
2
2
2
2
2
2
2
1
Heather FlyHatch
2
2
Daddy Long LegsHatch
2
3
3
2
Claret DunHatch
2
3
2
Murrough (Great Red Sedge)Hatch
2
3
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Atlantic Salmon fly box

Rougher, darker and more traditional. Stronger weighting on dark wets, bushy bob flies and commotion-making patterns.

Permits & access
Permit required — see local rules.
  • Premium managed fishery — advance booking through Grimersta Estate
  • Very limited availability
  • Fly only.
What's coming
Plan ahead
5-day outlook
Other water nearby · 3
Loch Morsgail
9.0 km
0
Brown trout · Salmon · Sea trout
Loch Langavat (Lewis)
15 km
0
Brown trout · Char · Salmon
Loch Roag System
5.0 km
Brown trout · Salmon · Sea trout
Gallery · 3
  1. Grimersta River - geograph.org.uk - 2639590
  2. Loch Grimersta on the Isle of Lewis, a chain loch of the Grimersta salmon fishery system, with hills in the distance.
    Loch Griomarstadh (Loch Grimersta), part of the Grimersta river and loch system, Isle of Lewis.
  3. Terrain map of the venue
    Terrain map
About this water

The Grimersta is extraordinary: in a good spate it can produce salmon catches that rival any river in Scotland, despite being barely a mile long. The system's magic lies in its chain of lochs which act as holding pools, and the short river which fish run through in hours rather than days after rain. Sea trout also run the system in good numbers. The fishing is managed as a premium let and commands high prices, but when it fires after a summer spate, there is nothing else quite like it in Scottish salmon fishing. Peat-stained moorland water defines this river. Atlantic salmon stocks are Category 3 (declining) — all salmon must be released.

Sea trout here

Summer-autumn runs, seasonal patterns vary by region

  • Loch
  • Peat
Why this score · for Atlantic Salmon
  • Temperature5230% weight
  • Flow6025% weight
  • Clarity8520% weight
  • Feeding Time1015% weight
  • Pressure8510% weight
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Salmon 11 February → 31 October

Sea trout: Variable seasonal (2026) — Grimersta — the most celebrated sea trout system in the British Isles historically. Lewis loch chain with a legendary record for very large sea trout. Stocks have collapsed under sea-lice pressure from west-coast salmon farms; catches are a fraction of their 1970s–80s peak. Still worth fishing carefully when conditions align, but the days of double-figure fish in numbers are gone. Catch-and-release mandatory under contemporary estate management.

Related guides
Scotland Playbookloch & river fishingThermal Layers & Troutreading depth and temperatureAtlantic Salmonsalmon tactics
Booking & contacts
At a glance

Grimersta River & Loch System is a spate river in Outer Hebrides / Lewis, Scotland. Its recorded elevation is about 44 m above sea level and the catchment geology is peat. The river is described as roughly 2 km long. Our data lists brown trout, salmon and sea trout here. It is classed as a salmon river. The salmon season is recorded as running from 11 February to 31 October. Best window recorded for anglers: June-September; best after summer spates. Core methods listed: short-line wet fly on the river; loch-style drift on the chain lochs; spate fishing with single-handed rod. Nearby waters in our listings include Loch Roag System at 5.0 km, Loch Morsgail at 9.0 km and Loch Langavat (Lewis) at 15 km.