Rules at a glance
- Free fishing
Water temperature for Rainbow Trout
Ideal15°C est.ideal 10–18°C
0°14°28°
How to fish it · for Rainbow Trout
When
Season runs 1 June to 14 October — deliberately late, because the Lys carries too much glacial meltwater to fish well before then. Mornings are clearer than afternoons once the glacier gets going for the day.
Where
The three-kilometre reserve above Gressoney-La-Trinité — pocket water and pools typical of a Monte Rosa torrent, restocked weekly.
Method
Bait, spinning or fly all permitted; no catch-and-release requirement. Minimum size 25cm, six fish per permit, up to three permits a day.
Kit
9 ft #5/6, floating line — nothing needs to be delicate here, the water is rarely gin-clear.
Why this works
Excellent — conditions well-balanced, with water temperature particularly in your favour.
Likely species
Mayflies
Mayflies- Blue-winged oliveMost likely#16–18 · DunDuns are up; a sherry spinner fall may follow.
- Large dark oliveAlso possible#14–16 · EmergerDead-drift the emerger — it's sitting in the film.
Caddisflies
Caddisflies- Net-spinning caddis (S. Europe)Most likelyLower confidence#12–14–16 · PupaWidespread riffle net-spinner; evening emergence.
- Satin sedgeAlso possibleLower confidence#12–14 · Egg-layingSkitter it at dusk — this one's fished, not dead-drifted.
Hatch timeline · todayPeak at 6pm
Hatch predictions
Today's headline hatch shown — see all 8 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 2 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 3 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalModerate 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
Large Dark OliveHatch
1
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Autumn OliveHatch
1
2
1
GrannomHatch
1
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Rainbow Trout fly box
Top
6-10 · Pattern
Swing, sub-surface
Permits & access
Permit required — see local rules.
- Managed tourist reserve — daily permit required, weekly stocking
- Minimum size 25cm, 6 fish per permit, maximum 3 permits per angler per day
- No catch-and-release requirement.
What's coming
Plan ahead
5-day outlook
Other water nearby · 4
Gallery · 1
Terrain map
The full read · show the working · for Rainbow Trout · confidence 90%
How the 85 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time85 × 13%11.1
Pressure75 × 7%5.3
Insect activity65 × 12%7.8
Conditions total= 85
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
Directions
Seasons & zones
- Rainbow trout 2026-06-01 → 2026-10-14
Related guides
Booking & contacts
Lys
Water temperature for Rainbow Trout
Ideal15°C est.ideal 10–18°C
0°14°28°
How to fish it · for Rainbow Trout
When
Season runs 1 June to 14 October — deliberately late, because the Lys carries too much glacial meltwater to fish well before then. Mornings are clearer than afternoons once the glacier gets going for the day.
Where
The three-kilometre reserve above Gressoney-La-Trinité — pocket water and pools typical of a Monte Rosa torrent, restocked weekly.
Method
Bait, spinning or fly all permitted; no catch-and-release requirement. Minimum size 25cm, six fish per permit, up to three permits a day.
Kit
9 ft #5/6, floating line — nothing needs to be delicate here, the water is rarely gin-clear.
Why this works
Excellent — conditions well-balanced, with water temperature particularly in your favour.
Likely species
Mayflies
- Blue-winged oliveMost likely#16–18 · DunDuns are up; a sherry spinner fall may follow.
- Large dark oliveAlso possible#14–16 · EmergerDead-drift the emerger — it's sitting in the film.
Caddisflies
- Net-spinning caddis (S. Europe)Most likelyLower confidence#12–14–16 · PupaWidespread riffle net-spinner; evening emergence.
- Satin sedgeAlso possibleLower confidence#12–14 · Egg-layingSkitter it at dusk — this one's fished, not dead-drifted.
Hatch timeline · todayPeak at 6pm
Hatch predictions
Today's headline hatch shown — see all 8 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 2 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 3 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalModerate 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
Large Dark OliveHatch
1
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Autumn OliveHatch
1
2
1
GrannomHatch
1
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Rainbow Trout fly box
Top
6-10 · Pattern
Swing, sub-surface
Permits & access
Permit required — see local rules.
- Managed tourist reserve — daily permit required, weekly stocking
- Minimum size 25cm, 6 fish per permit, maximum 3 permits per angler per day
- No catch-and-release requirement.
What's coming
Plan ahead
5-day outlook
Other water nearby · 4
Gallery · 1
Terrain map
The full read · show the working · for Rainbow Trout · confidence 90%
How the 85 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time85 × 13%11.1
Pressure75 × 7%5.3
Insect activity65 × 12%7.8
Conditions total= 85
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
Directions
Seasons & zones
- Rainbow trout 2026-06-01 → 2026-10-14
Related guides
Booking & contacts