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.

Fair · Grayling
F-Fly · Hook 18–22
Fairlive now
A side-water session, not the main event
River lifting fast on the rain. Take your time — read the water before you cast.
65% confidence
What moved it
  • Level1.01 mLifting fast
  • Water temp16.1°C
  • ClarityVery colouredColouring up
Today's fly
F-Fly
F-FlyHook 18–22
in season · matches water height
Conditions on the water
Live gauge
Level
Rising
1.01 m
Lifting fast
Water temp16.1°C
ClarityVery coloured
Weather17°C
WindNE 9 km/h
Pressure1029 hPa
Rain · recent22.9 mm
Rain · ahead8.0 mm

Live readings — water temperature is an estimate where the gauge does not record it.

Water temperature for Grayling
Warm — slow
16°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Midday window — grayling feed best from late morning into early afternoon.
Where
Work runs and glides — grayling shoal in the bottom third of the water column.
Method
Tight-line nymph the bottom third with weighted patterns.
Kit
10 ft #3 rod, floating line, long leader to 4 lb fluoro for nymphs.
Why this works
Fair — time of day is working for you, but river flow is the limiting factor today.
Hatch timeline · todayPeak at 6pm

Hatch predictions

Today's headline hatch shown — see all 10 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds with Pro.

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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
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
Grayling 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.
  • Alpine AAPPMA permits.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Arc
< 1 km
0
Brown trout · Grayling
Isère (Combe de Savoie)
45 km
0
Brown trout · Grayling
Gelon
48 km
0
Brown trout · Grayling
Plan d'Aval
16 km
Brown trout
Lac du Mont-Cenis
23 km
Brown trout · Char
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.

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.

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

WFD classification · FRDR10769

The full read · show the working · for Grayling · confidence 65%
How the 49 is built — score × weight = contribution
Temperature42 × 28%11.8
Flow30 × 22%6.6
Clarity45 × 18%8.1
Feeding Time90 × 13%11.7
Pressure80 × 7%5.6
Insect activity45 × 12%5.4
Conditions total= 49
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 4–14 °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