Spate · Mixed · West Wales / Carmarthenshire

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.
Contributor photo

River Cothi near Llwyn-y-ceiling

M J Roscoe - CC BY-SA 2.0

Tributary of the Towy and sewin river in its own right.

Prime · Brown Trout
CDC Emerger · 16-18
Primelive now
About as good as it gets
River steady at a fishable height. On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
75% confidence
What moved it
  • Level0.63 m
  • Water temp14.6°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-18
Upstream dry, in the film
Conditions on the water
Live gauge
Level
Steady
0.63 m
Water temp14.6°C
ClarityClear
Weather12°C
WindW 10 km/h
Pressure1022 hPa
Rain · recent4.8 mm
Rain · ahead0.9 mm

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

Water temperature for brown trout
Ideal
15°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
Excellent — water temperature is right today, though time of day could be better.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 7 active hatches hour by hour with Pro.

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Evidence
Survey-backed · regionalModerate confidence

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

Through the year
0–3 scale · July 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
BB
Black Beetle
14-18 · Pattern
Upstream dry, on top
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Teifi
18 km
Brown trout · Salmon · Sea trout
Towy (Tywi)
19 km
Brown trout · Salmon · Sea trout
Afon Llwchwr (Loughor)
28 km
79
Sea trout · Brown trout · Salmon
Afon Twrch
29 km
84
Brown trout
Tawe
31 km
Brown trout · Salmon · Sea trout
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
About this water

Tributary of the Towy and sewin river in its own right. Flashy spate river with rapid response (4 hours) — fishes brilliantly in a falling flood. Night fishing for sea trout June to August is productive (particularly July). Salmon also run. Fish the Cothi on the drop after spates with sinking-tip and medium tubes for salmon, smaller wets for sea trout. Tight timing window when flows are optimal; wait for rain and be ready. Atlantic salmon are under serious conservation pressure — Natural Resources Wales mandates catch-and-release for salmon on all rivers, so all fish must be returned.

  • Mixed
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 75%
How the 80 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time45 × 13%5.9
Pressure80 × 7%5.6
Insect activity52 × 12%6.2
Conditions total= 80
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Salmon1 April → 17 October
  • Trout3 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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Yorkshire & SpidersNorth Country methodsEuro Nymphingsubsurface methods
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