Karst · Limestone · Jura / Doubs, FR

Cusancin

A small clear river flowing over a low weir, lined with autumn trees, in the Cusancin valley, France.
Prime · Brown Trout
CDC Emerger · 16-20
New ruleReported 17 Jul 2026

Severe drought restrictions (crise) in force

A préfectoral drought order places this catchment's surface water at crise, the highest of France's four restriction tiers. Fishing itself is not named in the order, but flows are low and water-use restrictions are in force. Zone: Plateau calcaire jurassien (dépt 25).

Arrêté préfectoral n°37370 ↗

Temporary notices from official orders and recent fishery reports — they clear automatically once out of date. Always confirm locally before travelling.

Primelive now
About as good as it gets
Low and clear — careful approach country. Take your time — read the water before you cast.
90% confidence
What moved it
  • Level0.16 mLast reading 59 min ago
  • Water temp13.5°C
  • ClarityClear
Today's fly
CDC Emerger
CDC Emerger16-20
Dead-drift
Conditions on the water
Live gauge
Level
Steady
0.16 m
Last reading 59 min ago
Water temp13.5°C
ClarityClear
Weather13°C
WindS 13 km/h
Pressure1018 hPa
Rain · recent23.1 mm
Rain · ahead3.4 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
Ideal
14°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Through the open trout season. The Cusancin is small intimate karst water — read each lie carefully. Spring olives, summer sedges, autumn small flies.
Where
Pool tails, weeded glides, the cushion behind chalk boulders. The Cusancin is short and small-scale — short casts, careful approach.
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
Excellent — water temperature is right today, though time of day could be better.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 12 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(1)

Hatch predictions

Top prey shown — see all 2 with Pro.

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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 · 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
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Brown SedgeHatch
2
3
3
3
2
Small SpurwingHatch
2
3
3
3
2
Small Dark OliveHatch
2
3
3
3
2

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

Ranked for today
Brown Trout fly box
Permits & access
Permit required — see local rules.
  • AAPPMA permits required
  • Some beats private; fly-only and no-kill parcours on parts of the river
  • Low limits and short rods recommended.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Les piscicultures Côte
12 km
Rainbow trout
Doubs (France)
20 km
Brown trout · Grayling · Chub
Reverotte
27 km
81
Brown trout · Grayling
Lison
33 km
83
Brown trout · Grayling
Dessoubre
40 km
Brown trout · Grayling
Gallery · 2
  1. A small clear river flowing over a low weir, lined with autumn trees, in the Cusancin valley, France.
    cusancin
  2. Terrain map of the venue
    Terrain map
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 FRDR11271 (was a stale earlier-cycle value). Source: EEA WISE SWB_SurfaceWaterBody (discodata.eea.europa.eu), verified 2026-06-18.

WFD classification · FRDR11271

The full read · show the working · for Brown Trout · confidence 90%
How the 83 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity62 × 12%7.4
Conditions total= 83
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