Karst · Limestone · Jura / Haut-Jura (Saint-Claude)

Bienne

A calm, clear forest river with a gravel bank in the foreground and dense green trees lining both banks
Contributor photo

The Bienne river at Vaux-les-Saint-Claude, Haut-Jura, near the Gour aux Moines

Grosminou

The Bienne rises high on the Jura plateau above Morez and runs one hundred kilometres through limestone gorges, meadows, and finally to the Ain with the composure of water that knows precisely where it belongs.

Marginal · Brown Trout
CDC Emerger · 16-20
Marginallive now
Slow going — pick your moments
River temperature is the limiting factor today, not the flow. Fish dawn or dusk if you go at all, and handle everything with extra care.
80% confidence
What moved it
  • LevelDry recentlyNo gauge reading
  • Water temp20.2°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-20
Dead-drift
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp20.2°C
ClarityClear
Weather21°C
WindE 10 km/h
Pressure1015 hPa
Rain · recent0.0 mm
Rain · ahead13.2 mm

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

Water temperature for brown trout
Warm — slow
20°C est.ideal 1016°C
0°14°28°
How to fish it · for brown trout
When
Through the open trout season. Spring olives April through May; sedges through summer evenings; small dark flies into autumn close.
Where
Karst water through the Haut-Jura valley around Saint-Claude. Pool tails and the cushion behind limestone boulders.
Method
Upstream dry to spotted rising fish; long fine leader. The water reads clear — careful approach matters more than fly choice. Move slowly upstream, cast accurately, accept the result.
Kit
9 ft #4 — French karst-stream default. Floating line, 14 ft leader to 4 lb fluoro. Polarising glasses non-negotiable.
Why this works
⚠️ Water at 20.2°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots. Otherwise poor — water clarity is in the right range.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 3 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

See the full sub-surface read with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 3 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 · 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
Brown SedgeHatch
2
3
2
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Blue Winged OliveHatch
2
3
3
3
3
2
Mayfly (Green Drake)Hatch
2
2

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

Ranked for today
Brown Trout fly box
Gammarus Scud (Olive)
Gammarus Scud (Olive)
12-16 · Gammarus Scud
Dead-drift, sub-surface
Permits & access
Permit required — see local rules.
  • Cartes de pêche AAPPMA obligatoires
  • Parcours mouche seule et no-kill sur plusieurs secteurs balisés
  • Consultez les cartes de la FDAAPPMA du Jura pour les zones fermées.
What's coming
Plan ahead
5-day outlook
Water here around 20°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
  1. A calm, clear forest river with a gravel bank in the foreground and dense green trees lining both banks
    The Bienne river at Vaux-les-Saint-Claude, Haut-Jura, near the Gour aux Moines
  2. Terrain map of the venue
    Terrain map
About this water

The Bienne rises high on the Jura plateau above Morez and runs one hundred kilometres through limestone gorges, meadows, and finally to the Ain with the composure of water that knows precisely where it belongs. The upper reaches are pocket water — narrow, cold, quick-flowing — where wild Jura trout respond to anything cast in front of them without ceremony. The middle reaches around Saint-Claude open into glides and riffles where the fishing requires the restraint the water itself demands: fine tippets, small dries worked to genuinely rising fish, and an absolute refusal to hurry. The grayling below Saint-Claude hold in numbers that astonish, particularly in September when the season turns toward their favour. This is the river where French competition nymphing found its grammar — where team tactics and long leaders and Perdigon techniques were refined into precision. If you want to understand why European nymphing strategies took hold, spend a day watching the locals work this water. Autumn and spring offer the cleanest fishing; summer thermal buffering fades as the karst dries and the plateau warms. This is a river for patient anglers who understand that excellence, once found, is worth the discipline required to meet it.

  • Limestone
Water quality (WFD)
  • EcologyGood
  • ChemicalUnknown

WFD classification · FRDR499

The full read · show the working · for brown trout · confidence 80%
How the 26 is built — score × weight = contribution
Temperature23 × 28%6.4
Flow60 × 22%13.2
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity56 × 12%6.7
Limiting factor: Water temperature (20.2°C) is outside Brown Trout's preferred range (10–16°C)= 54
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
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.

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