Spate · Slate · North West Wales / Gwynedd

Mawddach

Mawddach terrain map
Terrain map

Small Snowdonia spate river with rapid response (3 hours) — quick to rise and quick to fall.

Species

Marginal — persistence required

River high but settled. Cover the water properly, fish each lie once.

40% confidence — limited data
Water temperature for sea trout
Cool — slow
6°C est.ideal 8–15°C
0°14°28°
Why this score · for sea trout
  • Temperature4028% weight
  • Flow3022% weight
  • Clarity4518% weight
  • Feeding Time5013% weight
  • Pressure857% weight
  • Prey Activity1112% weight
Conditions
Level
1.46 m
Water temp
5.7°C
Estimated
Clarity
Very coloured
Colouring up
Air temp
7°C
Wind
W 11 km/h
Light breeze
Pressure
1008 hPa
Rain · 48h
0.5 mm
No meaningful rain
Rain · ahead
26.8 mm
Heavy rain · next 48h

Live readings — water temperature is an estimate where the gauge does not record it.

How to fish it · for sea trout
When
June through September; July into August prime. Night fishing from full dark when water rises above 13°C. NRW classifies the sewin stock 'At Risk' across Wales — fish carefully if at all, treat C&R as a default. Fast 3-hour response means windows after rain are brief — book the river loosely and fish when it shapes up.
Where
Lower Mawddach pool tails through to the Barmouth tidal limit.
Method
Across-and-down on a floating line with small wets — Medicine, Teal Blue and Silver, Stoat's Tail. Steady swing through the tail-outs, never hurry.
Kit
10 ft #6/7, floating line, 8 to 10 lb fluoro tippet. Spare leader on a wrist spool. Headlamp sparingly; let your eyes adjust.
Why this works
Fair conditions. Pressure is favourable (85), Prey activity is weakest (11). ⏰ Sea trout become most active after dark, but this stretch closes at 20:53 — before that window fully opens. Fish hard in the last legal hour: overcast skies and warm evenings can bring fish on early even in fading light.
Through the year
0–3 scale · May highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Salmon runRun
1
2
2
2
2
2
2
1
Trout seasonSeason
1
2
2
2
2
2
1
March BrownHatch
2
3
2
GrannomHatch
2
2
Large StoneflyHatch
2
3
2
Yellow SallyHatch
2
3
2

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

Directions
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About this water

Small Snowdonia spate river with rapid response (3 hours) — quick to rise and quick to fall. Fish the window when water is in condition. Salmon and sea trout through season; brown trout in upper reaches. Fish sinking-tip with medium tubes for salmon, smaller wets for sea trout. Estuary near Barmouth concentrates migratory fish. Tight timing; wait for rain and be prepared.

  • Slate
Seasons & zones
  • Salmon20 March → 17 October
  • Trout3 March → 30 September

Sea trout: Variable seasonal (2026) — NRW At Risk classification. Small Snowdonia spate river where sea trout and salmon share the system. Fast response (3h) means windows after rain are brief but productive when they come. Stocks are down from historical levels.

Salmon: Negligible (2026) — NRW / EA 2024 Salmon Stocks Assessment classifies this Welsh principal salmon river 'at risk' — egg deposition below Conservation Limit. All Wales byelaws (in force 2020-2030) make catch & release mandatory. Conservation priority; not a salmon fishing destination. The Mawddach holds modest salmon runs but is classified at risk.

Other water nearby · 5
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