Chalk · Pas-de-Calais / Boulogne-sur-Mer

Liane

Liane venue image

The Liane runs about forty kilometres from its source near Quesques down through Samer to Boulogne-sur-Mer, a short coastal chalk stream that most fly anglers have never heard of.

Marginal · Brown Trout
Spent Spinner · 16-20
New ruleReported 25 Jul 2026

Severe drought restrictions (alerte renforcée) in force

The Bassins versants des fleuves côtiers du Boulonnais zone (Dept 62) is at alerte renforcée — the second-highest French drought tier — under a préfectoral arrêté. Fishing itself is not named as prohibited, but water is severely restricted and flows are likely very low; fish with care and check locally.

Arrêté préfectoral n°37479

Temporary notices from official orders and recent fishery reports — they clear automatically once out of date.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

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
  • LevelProxyvia Scie
  • Water temp18.7°C
  • ClarityClear
Today's fly
Spent Spinner
Spent Spinner16-20
Upstream dry
Conditions on the water
Proxy gauge
Level
Steady
Proxy
via Scie
Water temp18.7°C
ClarityClear
Weather19°C
WindN 6 km/h
Pressure1015 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

No gauge on this water — conditions are inferred from Scie. The trend transfers, the absolute level does not.

Water temperature for Brown Trout
Warm — slow
19°C est.ideal 1016°C
0°14°28°
How to fish it · for Brown Trout
When
Through the open trout season. Olives April through May; sedges through summer evenings.
Where
Pool tails and pocket water through the Boulogne valley. The Liane is small intimate chalk 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 18.7°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 5 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

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 · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
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

Classic French chalkstream fishing. Gin-clear, weed-rich, slow to moderate flow. Dry fly and sight nymphing dominate. Stronger sedge hatches than English equivalents. French tradition favours flush-sitting dries (comparaduns, CDC patterns) and upstream presentation.

Permits & access
Permit required — see local rules.
  • AAPPMA access
  • Sea trout fishing concentrated on lower meadows below Hesdin-l'Abbé — verify permit coverage of the tidal sections.
What's coming
Plan ahead
5-day outlook
Water here around 19°C. Nothing cooler within range — carry a thermometer.
Gallery · 1
  1. Terrain map of the venue
    Terrain map
About this water

The Liane runs about forty kilometres from its source near Quesques down through Samer to Boulogne-sur-Mer, a short coastal chalk stream that most fly anglers have never heard of. The upper half is proper brown trout water — clear, watercressed, rich with olives and sedges — and the lower half, below the tidal limit, gets a genuine sea trout run in late summer and autumn. It's not a famous river and it's not a large one, but it has the things that matter: stable water temperatures, proper fly life, wild fish. The AAPPMA beats around Hesdin-l'Abbé are good value for a day's fishing, and the sea trout fishing in the lower meadows in September, when the water drops and the fish come in on the bigger tides, is the kind of thing you remember.

Hatches & food

In chalk-spring and karst trout systems, generally stable temperatures broaden olive and other mayfly activity from early spring into autumn, with strong evening caddis, steady subsurface scuds and buzzers where clear groundwater and weedbeds develop, and terrestrials from meadow and woodland banks rounding out the food calendar, depending on how fast each river drops and clears after rain.

  • Chalk
Water quality (WFD)
  • EcologyModerate
  • ChemicalUnknown

WFD classification · FRAR30

The full read · show the working · for Brown Trout · confidence 80%
How the 36 is built — score × weight = contribution
Temperature44 × 28%12.3
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity63 × 12%7.6
Conditions total= 65
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Scieproxy
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
  • Trout 2nd Saturday of March3rd Sunday of September

Sea trout: Variable seasonal (2026)

Related guides
Casting instructors near here
Booking & contacts