Freestone · Mixed · Alps / Savoie (Haute Maurienne)

Arc

Arc venue image

Major Savoyard alpine river in Haute Maurienne.

Poor · Brown Trout
Small Perdigón · 16-20
Poorlive now
Not the day for it
River temperature is the limiting factor today, not the flow. This is not the day to push it. Check the thermal advice above before you head out.
90% confidence
What moved it
  • Level1.24 mLifting fast
  • Water temp22.2°C
  • ClarityVery colouredColouring up
Today's fly
Small Perdigón
Small Perdigón16-20
Euro-nymph
Conditions on the water
Live gauge
Level
Rising
1.24 m
Lifting fast
Water temp22.2°C
ClarityVery coloured
Weather20°C
WindE 5 km/h
Pressure1028 hPa
Rain · recent20.1 mm
Rain · ahead8.0 mm

Live readings only. Trends shown where the gauge supports them.

Water temperature for Brown Trout
Warm — slow
22.2°Cideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Through the open trout season — late spring through autumn. The Arc is glacial-fed from Haute Maurienne; fishes once meltwater eases.
Where
Pool tails and pocket water through the Maurienne valley. Glacial Alpine freestone — clear cold water, intimate scale.
Method
Upstream dry to risers; dry-dropper through the riffles. The water reads clear — long leader, fine tippet. Move slowly, cast accurately.
Kit
9 ft #4 — French freestone default. Floating line, 12 ft leader to 4 to 5 lb fluoro. Studded boots.
Why this works
Water at 22.2°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayPeak at 6pm

Hatch predictions

Today's headline hatch shown — see all 6 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 with Pro.

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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
GrannomHatch
2
2
Evening SedgeHatch
2
3
3
3
2
Alpine RhithrogenaHatch
1
2
2
1
Large Dark OliveHatch
1
2
2
1

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

Ranked for today
Brown Trout fly box

French nymph-first water. Fast current, technical presentation, weighted nymphs and emergers, with dry flies when fish rise.

Permits & access
Permit required — see local rules.
  • Savoie AAPPMA permits.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 2
Water here at 22.2°C — too warm to fish Brown Trout safely. These are cooler.
Lac du Mont-Cenis
23 km
~20°C
Brown trout · Char
Plan d'Aval
16 km
~22°C
Brown trout
Gallery · 1
  1. Terrain map of the venue
    Terrain map
About this water

Major Savoyard alpine river in Haute Maurienne. 7 km no-kill fly-fishing course with barbless-hook requirement. Snowmelt-dominated — May–June best when melt provides volume and insect life emerges. Technical pocket-water fishing in high-alpine terrain on granite freestone. Wild trout in pristine conditions. Check Savoie AAPPMA for permits and regulations.

Hatches & food

In true Alpine headwaters, trout feeding is squeezed into a short high-summer slot, with mountain olives and other mayflies following snowmelt, daytime stoneflies over rough, bouldery water, evening caddis on the warmest settled nights, and small buzzers keeping fish interested before, between and after the main up-wing and caddis hatches.

  • Mixed
Water quality (WFD)
  • Ecology: Good
  • Chemical: Unknown

WFD classification · FRDR361A

The full read · show the working · for Brown Trout · confidence 90%
How the 10 is built — score × weight = contribution
Temperature5 × 28%1.4
Flow55 × 22%12.1
Clarity15 × 18%2.7
Feeding Time70 × 13%9.1
Pressure80 × 7%5.6
Insect activity41 × 12%4.9
Limiting factor: Water temperature (22.2°C) is outside Brown Trout's preferred range (10–16°C)= 36
Can you trust it?
Water temperaturelive gauge readinggauge
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.
A drop and clear would lift the flow and clarity scores.
Directions
Apple MapsGoogle Maps
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
Grayling Playbookgrayling tacticsPyrenees PlaybookFrench riversEuro Nymphingsubsurface methods
Booking & contacts