Freestone · Mixed · Wallonia / Luxembourg Province, BE

Semois

Semois — File:Frahan JPG01.jpg
Good · Grayling
Pink Grayling Bug · Hook 16
Goodlive now
A proper day on the water
Low and clear — careful approach country. Stay small, stay accurate.
55% confidence
What moved it
  • Level0.01 mLast reading 1h ago
  • Water temp14.8°C
  • ClarityClear
Today's fly
Pink Grayling Bug
Pink Grayling BugHook 16
in season · matches water height · all-rounder
Conditions on the water
Live gauge
Level
Steady
0.01 m
Last reading 1h ago
Water temp14.8°C
ClarityClear
Weather17°C
WindS 18 km/h
Pressure1017 hPa
Rain · recent0.0 mm
Rain · ahead9.7 mm

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

Water temperature for Grayling
Warm — slow
15°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Midday window — grayling feed best from late morning into early afternoon.
Where
Work runs and glides — grayling shoal in the bottom third of the water column.
Method
Tight-line nymph the bottom third with weighted patterns.
Kit
10 ft #3 rod, floating line, long leader to 4 lb fluoro for nymphs.
Why this works
Good — water clarity is working for you, but time of day is the limiting factor today.
Likely species
Mayflies
Caddisflies
Gammarids
Hatch timeline · todayPeak at 6h

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
Trout seasonSeason
1
2
2
2
2
2
1
Grayling seasonSeason
2
1
1
2
2
2
2
2
2
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
2
2
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1

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

Ranked for today
Fly box · Grayling
Small Perdigón
Small Perdigón
Hook 14–18 · Fly
in season · matches water height
Permits & access
Permit required — see local rules.
  • Walloon permit required, but some stretches may sit under additional society, forest-zone or local rights structures depending on section.
What's coming
Plan ahead
5-day outlook
Other water nearby · 3
Lesse
27 km
Brown trout · Grayling
Pisciculture de Vendresse
35 km
Rainbow trout
Ourthe
44 km
62
Brown trout · Grayling
Gallery · 2
  1. Semois — File:Frahan JPG01.jpg
    File:Frahan JPG01.jpg
  2. Terrain map of the venue
    Terrain map
Water quality (WFD)
  • Ecology: Moderate
  • Chemical: Failing to achieve good
What this classification means

WFD re-coded 2026-06-18: prior id BERW06_SM01R was a wrong-basin code (no row in EEA WISE). Re-mapped to BERW17_SC28R 'Semois III' near the venue coordinate (49.85,5.08, Bouillon area). Status: EEA WISE 2022 (3rd RBMP). Confidence: medium — VERIFY reach against a map (Semois has 4 reaches I–IV). Source: discodata.eea.europa.eu.

WFD classification · BERW17_SC28R

The full read · show the working · for Grayling · confidence 55%
How the 66 is built — score × weight = contribution
Temperature65 × 28%18.2
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time15 × 13%2.0
Pressure80 × 7%5.6
Insect activity62 × 12%7.4
Conditions total= 66
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 4–14 °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
  • Trout 3e Saturday de March → 30 September
  • Grayling 1 June → 28 February
Related guides
Grayling Playbookgrayling tacticsEuro Nymphingsubsurface methods
Booking & contacts