Karst · Limestone · Franche-Comté / Doubs (Nans-sous-Ste-Anne)

Lison

Lison — Doubs Source du Lison 03
Contributor photo

Doubs Source du Lison 03

Zairon (https://commons.wikimedia.org/wiki/User:Zairon) - CC BY-SA

The Lison starts in the most theatrical fashion of any trout stream in France — as a full-sized river vaulting out of a cave mouth at Nans-sous-Sainte-Anne, clear as vodka and cold enough to make your wrist ache when you dip it in.

Poor · Brown Trout
CDC Emerger · 16-20
Poorlive now
Not the day for it
River temperature is the limiting factor today, not the flow. This is not the day to push it. Check the thermal advice above before you head out.
90% confidence
What moved it
  • LevelDry recentlyNo gauge reading
  • Water temp22.1°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-20
Dead-drift
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp22.1°C
ClarityClear
Weather22°C
WindSE 10 km/h
Pressure1015 hPa
Rain · recent0.0 mm
Rain · ahead12.8 mm

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

Water temperature for brown trout
Warm — slow
22°C est.ideal 1016°C
0°14°28°
How to fish it · for brown trout
When
Through the open trout season. Spring olives and sedges; summer evenings; small dark flies into autumn.
Where
Karst spring-fed water through the Doubs department. Pool tails and the cushion behind boulders. The Lison is small intimate water.
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 22.1°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayQuiet day

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Sub-surface · on the nymphunder the surface

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Beyond the hatch · worth watchingambient prey

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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.
  • AAPPMA du Lison
  • Some beats have fly-only and no-kill rules
  • Pay attention to closed zones protecting the source.
What's coming
Plan ahead
5-day outlook
Water here around 22°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
  1. Lison — Doubs Source du Lison 03
    Doubs Source du Lison 03
  2. Terrain map of the venue
    Terrain map
About this water

The Lison starts in the most theatrical fashion of any trout stream in France — as a full-sized river vaulting out of a cave mouth at Nans-sous-Sainte-Anne, clear as vodka and cold enough to make your wrist ache when you dip it in. Within fifty metres it's a proper river with proper fish. It joins the Loue after twenty-odd kilometres of mostly wooded, mostly wadeable limestone water, and along the way it holds wild brown trout and some of the most obliging grayling in the Jura. Obliging, that is, until they've been cast over once. After that they revert to being grayling. The upper river fishes like a spring creek — small flies, clean presentation, fish that sit pinned to the bottom between rises. The lower river opens into glides you can cover with a nymph rig and a reasonable expectation of a fish on every other run.

  • Limestone
Water quality (WFD)
  • EcologyGood
  • ChemicalUnknown

WFD classification · FRDR11865

The full read · show the working · for brown trout · confidence 90%
How the 12 is built — score × weight = contribution
Temperature6 × 28%1.7
Flow60 × 22%13.2
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity47 × 12%5.6
Limiting factor: Water temperature (22.1°C) is outside Brown Trout's preferred range (10–16°C)= 48
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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