Freestone · Mixed · Alps / Savoie (Cœur de Savoie), FR

Gelon

Le Gelon à Chamousset (été 2019)

AAPPMA-managed tributary of the Isère at Valgelon–La Rochette.

Poor · Brown Trout
Hare's Ear Nymph · 14-16
Closed season
Out of season. Try elsewhere.
Closed — confidence not applicable today.
What moved it
  • Level0.06 m
  • Water temp19.2°C
  • ClarityClear
Today's fly
Hare's Ear Nymph
Hare's Ear Nymph14-16
Upstream
Conditions on the water
Live gauge
Level
Steady
0.06 m
Water temp19.2°C
ClarityClear
Weather24°C
WindW 6 km/h
Pressure1021 hPa
Rain · recent0.0 mm
Rain · ahead4.5 mm

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

Water temperature for Brown Trout
Warm — slow
19°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
Water at 19.2°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Likely species
Caddisflies
Hatch timeline · todayPeak at 11am

Hatch predictions

Today's headline hatch shown — see all 11 active hatches hour by hour as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 3 as a supporter.

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Evidence
Survey-backed · regionalHigh confidence

Backed by regional invertebrate surveys; no sampling on this exact reach yet.

Through the year
0–3 scale · September 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
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.
  • AAPPMA permits.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 1
Water here around 19°C — probably warm enough to stress Brown Trout . These are likely cooler.
Lac d'Aiguebelette
27 km
~14°C
Brown trout · Char
Gallery · 2
  1. Le Gelon à Chamousset (été 2019)
  2. Terrain map of the venue
    Terrain map
About this water

AAPPMA-managed tributary of the Isère at Valgelon–La Rochette. Trout upstream, grayling in lower reaches. Alpine freestone on granite terrain. Spring through early autumn fishing. Mountain water with responsive character. Check local regulations for any restrictions or parcours requirements.

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: Moderate
  • Chemical: Unknown
What this classification means

WFD ecological status Good → Moderate corrected to EEA WISE 2022 (3rd RBMP) classification for waterbody FRDR10107 (was a stale earlier-cycle value). Source: EEA WISE SWB_SurfaceWaterBody (discodata.eea.europa.eu), verified 2026-06-18.

WFD classification · FRDR10107

The full read · show the working · for Brown Trout · confidence 80%
How the 0 is built — score × weight = contribution
Temperature22 × 28%6.2
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time60 × 13%7.8
Pressure80 × 7%5.6
Insect activity64 × 12%7.7
Limiting factor: Water temperature (19.2°C) is outside Brown Trout's preferred range (10–16°C)= 62
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
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