Mayflies
- Ecology: Good
- Chemical: Unknown
WFD classification · FRFRR245_3
Rules at a glance
- Day tickets
- Fly only
Water temperature for Brown Trout
Ideal15°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Late spring through early autumn — high alpine tributary, fishes only when snow has cleared. June through September realistically.
Where
Pocket water through the Cauterets valley. High Pyrenean character — clear cold water, intimate scale.
Method
Short upstream dry-dropper to wild fish in pocket water. The Marcadau is small mountain water — short casts, quiet wading.
Kit
8 ft #3 — small alpine stream. Floating line, 9 to 12 ft leader to 4 lb fluoro. Studded boots.
Why this works
Excellent — water temperature is right today, though insect activity could be better.
Likely species
Mayflies
- Blue-winged oliveMost likely#16–18 · DunDuns are up; a sherry spinner fall may follow.
- Green drakeAlso possibleLower confidence#8–10 · DunDuns are up — the Spent Gnat spinners fall at dusk.
Hatch timeline · todayPeak at 6am
Hatch predictions
Today's headline hatch shown — see all 7 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
See the full sub-surface read 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
Trout seasonSeason
1
2
2
2
2
2
1
Grayling seasonSeason
1
2
2
2
1
Alpine RhithrogenaHatch
2
3
3
2
Sculpin / Baitfish (Rivers)Hatch
2
3
3
3
3
3
3
3
2
Large Dark OliveHatch
1
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
Brown Trout fly box
Permits & access
Permit required — see local rules.
- AAPPMA permits
- Fly-only sections common in Pyrenees.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 2
Cauterets, vallee du Marcadau Terrain map
Water quality (WFD)
The full read · show the working · for Brown Trout · confidence 90%
How the 85 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity56 × 12%6.7
Conditions total= 85
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
Directions
Seasons & zones
- Trout 2nd Saturday of March → 3rd Sunday of September
- Grayling 3rd Saturday of May → 3rd Sunday of September
France national rule: grayling opens 3rd Saturday of May in all waters. In 1st category (salmonid) rivers, grayling closes with the trout season on the 3rd Sunday of September. Departmental regulations may impose additional restrictions. Always check the relevant département's 2026 arrêté préfectoral.
Related guides
Booking & contacts
Gave du Marcadau
Water temperature for Brown Trout
Ideal15°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Late spring through early autumn — high alpine tributary, fishes only when snow has cleared. June through September realistically.
Where
Pocket water through the Cauterets valley. High Pyrenean character — clear cold water, intimate scale.
Method
Short upstream dry-dropper to wild fish in pocket water. The Marcadau is small mountain water — short casts, quiet wading.
Kit
8 ft #3 — small alpine stream. Floating line, 9 to 12 ft leader to 4 lb fluoro. Studded boots.
Why this works
Excellent — water temperature is right today, though insect activity could be better.
Likely species
Mayflies
- Blue-winged oliveMost likely#16–18 · DunDuns are up; a sherry spinner fall may follow.
- Green drakeAlso possibleLower confidence#8–10 · DunDuns are up — the Spent Gnat spinners fall at dusk.
Hatch timeline · todayPeak at 6am
Hatch predictions
Today's headline hatch shown — see all 7 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
See the full sub-surface read 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
Trout seasonSeason
1
2
2
2
2
2
1
Grayling seasonSeason
1
2
2
2
1
Alpine RhithrogenaHatch
2
3
3
2
Sculpin / Baitfish (Rivers)Hatch
2
3
3
3
3
3
3
3
2
Large Dark OliveHatch
1
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
Brown Trout fly box
Permits & access
Permit required — see local rules.
- AAPPMA permits
- Fly-only sections common in Pyrenees.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 2
Cauterets, vallee du Marcadau Terrain map
Water quality (WFD)
- Ecology: Good
- Chemical: Unknown
WFD classification · FRFRR245_3
The full read · show the working · for Brown Trout · confidence 90%
How the 85 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity56 × 12%6.7
Conditions total= 85
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
Directions
Seasons & zones
- Trout 2nd Saturday of March → 3rd Sunday of September
- Grayling 3rd Saturday of May → 3rd Sunday of September
France national rule: grayling opens 3rd Saturday of May in all waters. In 1st category (salmonid) rivers, grayling closes with the trout season on the 3rd Sunday of September. Departmental regulations may impose additional restrictions. Always check the relevant département's 2026 arrêté préfectoral.
Related guides
Booking & contacts