Freestone · Mixed · Alps / Savoie (Haute Maurienne), FR

Arc

Arc à Saint-Michel-de-Maurienne dans l'après-midi (juillet 2022) 2

Major Savoyard alpine river in Haute Maurienne.

Poor · Grayling
Pink Grayling Bug · Hook 16
Closed season
Out of season. Try elsewhere.
Closed — confidence not applicable today.
What moved it
  • Level0.47 mLast reading 3h ago
  • Water temp5.1°C
  • ClarityClear
Today's fly
Pink Grayling Bug
Pink Grayling BugHook 16
in season · all-rounder
Conditions on the water
Live gauge
Level
Steady
0.47 m
Last reading 3h ago
Water temp5.1°C
ClarityClear
Weather1°C
WindS 5 km/h
Pressure1016 hPa
Rain · recent14.9 mm
Rain · ahead7.2 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Grayling
Ideal
5°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Autumn through November prime.
Where
Faster runs and the heads of riffles through the middle valley.
Method
Euro-nymphing through the deeper pockets; switch to dries when sedges or olives come off in autumn afternoons.
Kit
10 ft #3 nymphing rod for the deep pockets; 9 ft #4 for dries. 4 to 5 lb fluoro tippet, 12 ft leader.
Likely species
Gammarids
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 2 active hatches hour by hour as a supporter.

Start free trial

14-day free trial. Cancel anytime.

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 4 guilds as a supporter.

Start free trial

14-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 · November 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
Evening SedgeHatch
2
3
3
3
2
Alpine RhithrogenaHatch
1
2
2
1
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
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.

Small Perdigón
Small Perdigón
Hook 14–18 · Fly
in season
Permits & access
Permit required — see local rules.
  • Savoie AAPPMA permits.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Arc
< 1 km
Brown trout · Grayling
Lac du Mont-Cenis
11 km
Brown trout · Char
Plan d'Aval
23 km
Brown trout
Dora Baltea (No-Kill, Chambave-Verrayes)
58 km
Brown trout · Marble trout · Grayling
Ayasse
59 km
Rainbow trout
Gallery · 3
  1. Arc à Saint-Michel-de-Maurienne dans l'après-midi (juillet 2022) 2
  2. Arc à Bessans en direction de sa source (juillet 2023)
  3. Terrain map of the venue
    Terrain map
About this water

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 Grayling · confidence 55%
How the 0 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time15 × 13%2.0
Pressure80 × 7%5.6
Insect activity26 × 12%3.1
Conditions total= 72
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
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
At a glance

Arc is a freestone river in Alps / Savoie (Haute Maurienne), France. It sits at about 1,703 m above sea level. The river is described as roughly 127 km long. Our data lists brown trout and grayling here. The trout season is recorded as running from 2nd Saturday of March to 3rd Sunday of September. The grayling season is recorded as running from 3rd Saturday of May to 3rd Sunday of September. Best window recorded for anglers: June–September. Core methods listed: Euro nymphing; dry fly. Level and flow data for this water is linked from 1 gauge. Its Water Framework Directive ecological status is recorded as good. Access is recorded as day tickets through the local AAPPMA (angling association). Nearby waters in our listings include Arc at < 1 km, Lac du Mont-Cenis at 11 km and Plan d'Aval at 23 km.