- Ecology: Moderate
- Chemical: Unknown
What this classification means
NRW WFD Cycle 3 — Seiont: Moderate ecological status. Status corrected 2026-06-18 (was recorded Good). Source: NRW DataMapWales classification layer.
NRW (Wales) · UKGB110065054040
Rules at a glance
- Free fishing
- Fly only
Water temperature for Atlantic Salmon
Warm — slow19°C est.ideal 10–14°C
0°14°28°
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
Water at 19°C — above the atlantic salmon caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayPeak at 6am
Hatch predictions
Today's headline hatch shown — see all 7 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 2 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 2 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalHigh confidence
Backed by regional invertebrate surveys; no sampling on this exact reach yet.
Through the year
0–3 scale · August 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
Daddy Long LegsHatch
2
3
2
March BrownHatch
2
3
2
GrannomHatch
2
2
Large StoneflyHatch
2
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Atlantic Salmon fly box
Beats · 1
SGLL Fishing Society — Seiont system day ticketsAccess varies
SGLL Fishing Society sells a single Passport day ticket that covers all of its Seiont-system beats — Cwm Y Glo Crawia, Glan Gwna, Glanrafon, Glanrafon Pont Rug, and Llyn Garnage to Sea.
Visit official site ↗What's coming
Plan ahead
5-day outlook
Water here around 19°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
The Afon Seiont near Caernarfon, north Wales. Terrain map
Water quality (WFD)
Why this score · for Atlantic Salmon
- Temperature1430% weight
- Flow6025% weight
- Clarity9520% weight
- Feeding Time8515% weight
- Pressure8510% weight
Directions
Seasons & zones
- Salmon 1 April → 17 October
- Sea trout 3 March → 17 October
- Trout 3 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.
Related guides
Casting instructors near here
Booking & contacts
Seiont
Water temperature for Atlantic Salmon
Warm — slow19°C est.ideal 10–14°C
0°14°28°
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
Water at 19°C — above the atlantic salmon caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayPeak at 6am
Hatch predictions
Today's headline hatch shown — see all 7 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 2 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 2 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalHigh confidence
Backed by regional invertebrate surveys; no sampling on this exact reach yet.
Through the year
0–3 scale · August 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
Daddy Long LegsHatch
2
3
2
March BrownHatch
2
3
2
GrannomHatch
2
2
Large StoneflyHatch
2
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Atlantic Salmon fly box
Beats · 1
SGLL Fishing Society — Seiont system day ticketsAccess varies
SGLL Fishing Society sells a single Passport day ticket that covers all of its Seiont-system beats — Cwm Y Glo Crawia, Glan Gwna, Glanrafon, Glanrafon Pont Rug, and Llyn Garnage to Sea.
Visit official site ↗What's coming
Plan ahead
5-day outlook
Water here around 19°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
The Afon Seiont near Caernarfon, north Wales. Terrain map
Water quality (WFD)
- Ecology: Moderate
- Chemical: Unknown
What this classification means
NRW WFD Cycle 3 — Seiont: Moderate ecological status. Status corrected 2026-06-18 (was recorded Good). Source: NRW DataMapWales classification layer.
NRW (Wales) · UKGB110065054040
Why this score · for Atlantic Salmon
- Temperature1430% weight
- Flow6025% weight
- Clarity9520% weight
- Feeding Time8515% weight
- Pressure8510% weight
Directions
Seasons & zones
- Salmon 1 April → 17 October
- Sea trout 3 March → 17 October
- Trout 3 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.
Related guides
Casting instructors near here
Booking & contacts