Spate · Mixed · West Wales / Carmarthenshire, GB-WLS

Cothi

A wide clear run of the River Cothi near Llwyn-y-ceiling in winter low water, with wooded valley sides and pale gravel banks.
Poor · Brown Trout
CDC Emerger · 16-18
Poorlive now
Not the day for it
River temperature is the limiting factor today, not the flow. This is not the day to push it. Check the thermal advice above before you head out.
80% confidence
What moved it
  • Level0.46 mLast reading 5h ago
  • Water temp21.0°C
  • ClarityClear
Today's fly
CDC Emerger
CDC Emerger16-18
Upstream dry, in the film
Conditions on the water
Live gauge
Level
Steady
0.46 m
Last reading 5h ago
Water temp21.0°C
ClarityClear
Weather20°C
WindN 19 km/h
Pressure1020 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Brown Trout
Warm — slow
21°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Water at 21°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayPeak at 6pm

Hatch predictions

Today's headline hatch shown — see all 10 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

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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 · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Salmon runRun
1
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
Brown Trout fly box
What's coming
Plan ahead
5-day outlook
Water here around 21°C. Nothing cooler within range — carry a thermometer.
Gallery · 6
  1. A wide clear run of the River Cothi near Llwyn-y-ceiling in winter low water, with wooded valley sides and pale gravel banks.
    River Cothi near Llwyn-y-ceiling
  2. The River Cothi flowing through the village of Pumsaint in Carmarthenshire, tree-lined banks in autumn light.
    Afon Cothi in Pumsaint
  3. The Afon Cothi viewed from Pont Prenllwyd in October, autumnal wooded valley and fast-flowing water over boulders.
    Afon Cothi from Pont Prenllwyd
  4. The River Cothi at Pont-ar-gothi in spring, a broad calm glide with wooded banks and the old bridge behind.
    The River Cothi at Pont-ar-gothi
  5. Looking upstream along the Afon Cothi near Llanegwad in November, bare alders overhanging slow dark water.
    Afon Cothi near Llanegwad
  6. Terrain map of the venue
    Terrain map
Water quality (WFD)
  • Ecology: Good
  • Chemical: Unknown
What this classification means

NRW WFD Cycle 3 — Cothi (confluence with Marlais to confluence with Tywi): Good ecological status; the lower Cothi sewin water. Corrected 2026-06-18 from a Clydach-tributary tag. Source: NRW DataMapWales WFD Cycle 3 classification layer.

NRW (Wales) · GB110060036300

The full read · show the working · for Brown Trout · confidence 80%
How the 21 is built — score × weight = contribution
Temperature14 × 28%3.9
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time60 × 13%7.8
Pressure80 × 7%5.6
Insect activity57 × 12%6.8
Limiting factor: Water temperature (21°C) is outside Brown Trout's preferred range (10–16°C)= 59
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Salmon 1 April → 17 October
  • Trout 3 March → 30 September

Sea trout: Variable seasonal (2026) — Towy tributary rated At Risk by NRW. Sea trout present and fishable June–August but stocks share the wider Towy system decline. Night fishing after summer rain is the productive window; low clear water is unproductive.

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 Cothi is a Tywi tributary and shares its at-risk status.

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