Freestone · Granite · Savoie / Alps (Tarentaise valley)

Arc (Bessans reach)

The Arc descends from the high Vanoise through Bessans into a valley where snowmelt and granite are the dominant geology.

Good · Brown Trout
Small Perdigón · 16-20
Goodlive now
A proper day on the water
Low and clear — careful approach country. Stay small, stay accurate.
90% confidence
What moved it
  • LevelDry recentlyNo gauge reading
  • Water temp17.0°C
  • ClarityClear
Today’s fly
Small Perdigón
Small Perdigón16-20
Euro-nymph
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp17.0°C
ClarityClear
Weather16°C
WindSE 4 km/h
Pressure1021 hPa
Rain · recent0.0 mm
Rain · ahead13.0 mm

No gauge on this water — readings are regional estimates from weather, not a live gauge.

Water temperature for brown trout
Warm — slow
17°C est.ideal 10–16°C
0°14°28°
How to fish it · for brown trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Good — water clarity is right today, though insect activity could be better.
Hatch timeline · todayPeak at 6pm

Hatch predictions

Today's headline hatch shown — see all 4 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

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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 · July 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.
  • Cartes de pêche AAPPMA alpines.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Arc
< 1 km
Brown trout · Grayling
Plan d'Aval
16 km
Brown trout
Tarentaine
19 km
Brown trout · Grayling
Lac du Mont-Cenis
23 km
Brown trout · Char
Isère (Combe de Savoie)
45 km
Brown trout · Grayling
About this water

The Arc descends from the high Vanoise through Bessans into a valley where snowmelt and granite are the dominant geology. Short-season alpine water — May and June critical when melt provides volume and insect life emerges. Wild brown trout and grayling in cold, oxygenated freestone. Technical mountain fishing with small dries and nymphs. Check access to beats near Bessans.

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

WFD classification · FRDR10769

The full read · show the working · for brown trout · confidence 90%
How the 73 is built — score × weight = contribution
Temperature77 × 28%21.6
Flow60 × 22%13.2
Clarity95 × 18%17.1
Feeding Time70 × 13%9.1
Pressure80 × 7%5.6
Insect activity56 × 12%6.7
Conditions total= 73
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout2nd Saturday of March → 3rd Sunday of September
  • Grayling3rd 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