Rules at a glance
- Free fishing
- Fly only
Water temperature for Brown Trout
Warm — slow18°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
From the 2nd Saturday of March opening into early September. Best window April–June with small olives and grannom; shoulder through summer.
Where
Upper reaches around La Ferté-Gaucher and upstream towards Esternay. Pool tails, faster glides, and the seams behind overhanging willow on the smaller upper beats.
Method
Upstream dry to risers; dry-dropper through the riffles. Walk-and-spot.
Kit
9 ft #4 (or 8 ft #3 on tighter beats), floating line, 12 ft leader to 3–4 lb fluoro.
Why this works
Water at 18°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
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(1)
Hatch predictions
Top prey shown — see all 3 with Pro.
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 · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
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
Brown Trout fly box
Permits & access
Permit required — see local rules.
- 1ère catégorie above Moulin de Montblin (La Ferté-Gaucher)
- AAPPMA permit + carte de pêche required
- Check the Seine-et-Marne federation's annual notice for category boundaries, catch limits and method restrictions.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 2
Water here around 18°C — probably warm enough to stress Brown Trout . These are likely cooler.
The full read · show the working · for Brown Trout · confidence 80%
How the 40 is built — score × weight = contribution
Temperature42 × 28%11.8
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity57 × 12%6.8
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 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 2nd Saturday of March → 3rd Sunday of September
Related guides
Booking & contacts
Grand Morin (Upper)
Water temperature for Brown Trout
Warm — slow18°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
From the 2nd Saturday of March opening into early September. Best window April–June with small olives and grannom; shoulder through summer.
Where
Upper reaches around La Ferté-Gaucher and upstream towards Esternay. Pool tails, faster glides, and the seams behind overhanging willow on the smaller upper beats.
Method
Upstream dry to risers; dry-dropper through the riffles. Walk-and-spot.
Kit
9 ft #4 (or 8 ft #3 on tighter beats), floating line, 12 ft leader to 3–4 lb fluoro.
Why this works
Water at 18°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
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(1)
Hatch predictions
Top prey shown — see all 3 with Pro.
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 · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
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
Brown Trout fly box
Permits & access
Permit required — see local rules.
- 1ère catégorie above Moulin de Montblin (La Ferté-Gaucher)
- AAPPMA permit + carte de pêche required
- Check the Seine-et-Marne federation's annual notice for category boundaries, catch limits and method restrictions.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 2
Water here around 18°C — probably warm enough to stress Brown Trout . These are likely cooler.
The full read · show the working · for Brown Trout · confidence 80%
How the 40 is built — score × weight = contribution
Temperature42 × 28%11.8
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity57 × 12%6.8
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 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 2nd Saturday of March → 3rd Sunday of September
Related guides
Booking & contacts