Gammarids
Brown trout and grayling in limestone-rich water with good hatches. Some sections experience kayak traffic in summer—fish early or late. Club permits required.
- Limestone
Rules at a glance
- Day tickets
Water temperature for Grayling
Ideal7°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 temperature is working for you, but time of day is the limiting factor today. Grayling feeds actively in cold water — peak winter sport.
Likely species
Hatch timeline · todayPeak at 11am
12pm(now) — Autumn Needle Fly
Stage: Creeping nymphsApproach: Heavy nymphActivity: 29%
Also:Black Midge25%
Peak emergence window4 food groups active
Peak activity at 11am — Autumn Needle Fly (Autumn Needle Fly, Peak emergence window)
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 4 guilds as a supporter.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Supporters see what else is on the menu.
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 · November 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
Grayling fly box
A proper Ardennes river-trout pack for Wallonia, centred on clear to lightly coloured rivers with trout and some classic fly-fishing culture.
Hook 14–18 · Fly
in season
Permits & access
Permit required — see local rules.
- Permis de pêche (Wallonia) / Visverlof (Flanders)
- Foreign anglers can purchase a Walloon fishing permit (permis de pêche) online or at post offices without residency requirements
- For Flemish waters, the visverlof is similarly available
- No prior fishing exam required in either region.
What's coming
Plan ahead
5-day outlook
Other water nearby · 3
Gallery · 2
Lesse Terrain map
About this water
Water quality (WFD)
- Ecology: Moderate
- Chemical: Unknown
WFD classification · BERW06_LE07R
The full read · show the working · for Grayling · confidence 55%
How the 71 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time10 × 13%1.3
Pressure80 × 7%5.6
Insect activity28 × 12%3.4
Conditions total= 71
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
Seasons & zones
- Trout 3rd Saturday of March → 30 September
- Grayling 1 June → 28 February
Related guides
Booking & contacts
Lesse
Ardennes river famous for the caves at Han-sur-Lesse where the river disappears underground.
Water temperature for Grayling
Ideal7°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 temperature is working for you, but time of day is the limiting factor today. Grayling feeds actively in cold water — peak winter sport.
Likely species
Hatch timeline · todayPeak at 11am
12pm(now) — Autumn Needle Fly
Stage: Creeping nymphsApproach: Heavy nymphActivity: 29%
Also:Black Midge25%
Peak emergence window4 food groups active
Peak activity at 11am — Autumn Needle Fly (Autumn Needle Fly, Peak emergence window)
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 4 guilds as a supporter.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Supporters see what else is on the menu.
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 · November 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
Grayling fly box
A proper Ardennes river-trout pack for Wallonia, centred on clear to lightly coloured rivers with trout and some classic fly-fishing culture.
Hook 14–18 · Fly
in season
Permits & access
Permit required — see local rules.
- Permis de pêche (Wallonia) / Visverlof (Flanders)
- Foreign anglers can purchase a Walloon fishing permit (permis de pêche) online or at post offices without residency requirements
- For Flemish waters, the visverlof is similarly available
- No prior fishing exam required in either region.
What's coming
Plan ahead
5-day outlook
Other water nearby · 3
Gallery · 2
Lesse Terrain map
About this water
Brown trout and grayling in limestone-rich water with good hatches. Some sections experience kayak traffic in summer—fish early or late. Club permits required.
- Limestone
Water quality (WFD)
- Ecology: Moderate
- Chemical: Unknown
WFD classification · BERW06_LE07R
The full read · show the working · for Grayling · confidence 55%
How the 71 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time10 × 13%1.3
Pressure80 × 7%5.6
Insect activity28 × 12%3.4
Conditions total= 71
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
Seasons & zones
- Trout 3rd Saturday of March → 30 September
- Grayling 1 June → 28 February
Related guides
Booking & contacts
At a glance
Lesse is a freestone river in Wallonia / Namur Province, Belgium. Its recorded elevation is about 153 m above sea level and the catchment geology is limestone. Our data lists brown trout and grayling here. The trout season is recorded as running from 3rd Saturday of March to 30 September. The grayling season is recorded as running from 1 June to 28 February. Best window recorded for anglers: trout: 3rd Saturday of March (Wallonia) – 30 September (Wallonia); grayling: 1 June (Wallonia) – 28 February (Wallonia). Core methods listed: Nymph fishing; Dry fly; Wet fly / soft hackle. Level and flow data for this water is linked from 2 gauges. Its Water Framework Directive ecological status is recorded as moderate. Nearby waters in our listings include Ourthe at 27 km, Semois at 31 km and Amblève at 57 km.