Spate · Slate · North Wales / Gwynedd

Seiont

No photos yet for this water.

Short, sharp river out of Llyn Padarn under Yr Wyddfa, through Caernarfon and into the Menai Strait.

Species

A good day — worth the effort

Low and clear — careful approach country. Small and bright, long leader, careful approach.

50% confidence in this read
Water temperature for atlantic salmon
Ideal
10°C est.ideal 10–14°C
0°14°28°
Why this score · for atlantic salmon
  • Temperature10030% weight
  • Flow6025% weight
  • Clarity9520% weight
  • Feeding Time1015% weight
  • Pressure8510% weight
Conditions
Level
Dry recently
No gauge reading
Water temp
10.4°C
Estimated
Clarity
Clear
Air temp
18°C
Wind
SE 5 km/h
Calm
Pressure
1030 hPa
Rain · 24h
0.0 mm
No rain
Rain · ahead
0.0 mm
No meaningful rain · next 48h

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

How to fish it · for atlantic salmon
When
Summer through autumn. Fish on the drop after rain — 6 to 12 hours into a falling spate.
Where
Lower Seiont pools through Caernarfon and above the tidal limit.
Method
Small doubles 10 to 12 across-and-down on a floating line; small tubes on a sink-tip in spring or coloured water. Fish the named lies in each pool, working systematically before moving on. Mandatory catch-and-release under NRW byelaw — every salmon goes back.
Kit
10 ft #7/8 single-hander or 11 ft switch — small spate scale; double-handers are wasted on these rivers. Floating line plus light sink-tip. 10 to 12 lb fluoro tippet.
Why this works
Good conditions. Temperature is favourable (100), Feeding time is weakest (10).
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
1
Sea trout 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

Short, sharp river out of Llyn Padarn under Yr Wyddfa, through Caernarfon and into the Menai Strait. The Seiont is the salmon and sea-trout backbone of a wider three-river system with the Gwyrfai and Llyfni; Arctic char persist in the catchment in Llyn Cwellyn. Quick to rise, quicker to fall — Eryri spate logic in compact form.

  • Slate
Seasons & zones
  • Salmon1 April → 17 October
  • Sea trout3 March → 17 October
  • Trout3 March → 30 September

Sea trout: Variable seasonal (2026) — Salmon and sewin backbone of the Seiont/Gwyrfai/Llyfni catchment per NRW. Compact spate with brief windows; All-Wales At Risk picture applies.

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