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.

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

Prime · Sea Trout
Black & Silver Tube · 1-2 inch
Primelive now
Prime conditions — go now
River steady at a fishable height. Settled and taking. Work it methodically.
90% confidence
What moved it
  • Level0.57 mLast reading 21h ago
  • Water temp15.4°C
  • ClarityClear
Today's fly
BS
Black & Silver Tube1-2 inch
In deep pools and dark water, silhouette and contrast do the work colour cannot. A fly that reads as black against depth is enough. Fish it broadside, hold the swing, let it hang at the dangle — that is when the best fish take.
Conditions on the water
Live gauge
Level
Steady
0.57 m
Last reading 21h ago
Water temp15.4°C
ClarityClear
Weather19°C
WindSE 32 km/h
Pressure1006 hPa
Rain · recent3.3 mm
Rain · ahead7.3 mm

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

Water temperature for Sea Trout
Warm — slow
15°C est.ideal 8–15°C
0°14°28°
How to fish it · for Sea Trout
When
From dusk into the first half of the night.
Where
Deeper pools and slower glides · hold water and current seams.
Method
Fish dark patterns on a sink-tip or lightly sunk line, especially near structure.
Kit
10 ft #6/7 rod, floating line with a sink-tip option, 8–10 lb fluoro tippet for the swing.
Why this works
Excellent — conditions well-balanced, with time of day particularly in your favour.
Likely species
Stoneflies
Caddisflies
Gammarids
Hatch timeline · todayPeak at 2pm

Hatch predictions

Today's headline hatch shown — see all 12 active hatches hour by hour as a supporter.

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Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 4 guilds as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 3 as a supporter.

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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 · September 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
March BrownHatch
2
3
2
CapererHatch
2
3
3
2
Heather FlyHatch
2
2
Autumn DunHatch
2
3
2

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

Ranked for today
Sea Trout fly box

Shrimp fly theme — fished swing, wet_fly_swing

BS
Black & Silver TubeTop
1-2 inch · Tube
In deep pools and dark water, silhouette and contrast do the work colour cannot. A fly that reads as black against depth is enough. Fish it broadside, hold the swing, let it hang at the dangle — that is when the best fish take.
Medicine Fly
Medicine Fly
8-12 · Streamer
Slim and mobile — fished sunk through the pool when surface work is not producing. Consistently takes fish that will not come to the surface.
SF
Snake Fly (Black)
2-4 inch · Streamer
A mobile eel-like profile that undulates through deep pools — effective when sea trout are lying deep and not responding to conventional wets.
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
Amman
21 km
Brown trout · Sea trout · Salmon
Afon Llwchwr (Loughor)
28 km
Sea trout · Brown trout · Salmon
Afon Twrch
29 km
Brown 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.

Sea trout here

Summer-autumn runs (June–September), primarily nocturnal

  • 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 Sea Trout · confidence 90%
How the river scores — hydrology factors
Water heightLow But Fishable-1.1
Recent riseNone0.0
Falling after liftFalling Slightly After Lift+3.4
Water temperatureCool To Moderate+3.5
Time in seasonLate Season+1.9
ClarityClearing+2.4
Hydrology base10.1
Will they take?Willingcaps the band

Fish should be willing to take — clearing, stained water.

Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
What would change the calculation
No prolonged stable spell before the current rise.
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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