Freestone · Mixed · Pyrénées-Atlantiques

Gave d'Ossau

A wide clear river with turquoise water flowing over gravel past a forested limestone ridge in the Pyrenees
Contributor photo

The Gave d'Ossau at Castet

Capbourrut

The Gave d'Ossau is upper Béarn — snowmelt-fed Pyrenean freestone dropping out of the Pic du Midi country and running north through the valley towards Oloron, where it feeds the bigger Gave system.

Marginal · Brown Trout
CDC Emerger · 16-18
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 temp19.5°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-18
Dead-drift
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp19.5°C
ClarityClear
Weather21°C
WindW 14 km/h
Pressure1018 hPa
Rain · recent0.0 mm
Rain · ahead11.3 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 once snowmelt drops; sedges through summer; small dark flies into autumn close.
Where
Pool tails and pocket water through the Ossau valley. Pyrenean piedmont character — clear water, intimate scale.
Method
Upstream dry to risers; nymph the deeper pockets between hatches. Short casts, quiet wading.
Kit
9 ft #4 — French freestone default. Floating line, 12 ft leader to 4 to 5 lb fluoro. Studded boots.
Why this works
⚠️ Water at 19.5°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 2 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 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
GrannomHatch
2
2
Evening SedgeHatch
2
3
3
3
2
Alpine RhithrogenaHatch
1
2
2
1
Large Dark OliveHatch
1
2
2
1

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

Ranked for today
Brown Trout fly box
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 1
Water here around 20°C — probably warm enough to stress brown trout. These are likely cooler.
Gallery · 2
  1. A wide clear river with turquoise water flowing over gravel past a forested limestone ridge in the Pyrenees
    The Gave d'Ossau at Castet
  2. Terrain map of the venue
    Terrain map
About this water

The Gave d'Ossau is upper Béarn — snowmelt-fed Pyrenean freestone dropping out of the Pic du Midi country and running north through the valley towards Oloron, where it feeds the bigger Gave system. It carries wild brown trout throughout its middle and upper reaches and holds them in the kind of fast, cold water that rewards anyone willing to get into it properly. The reaches around Laruns and Sévignacq-Meyracq are fly-only no-kill, barbless on a single hook, and the AAPPMA has been managing the fishing with more care than most. Tight-line nymphing with beadheads is the staple for the pocket water; by late June the caddis and olives start triggering genuine dry-fly windows in the evenings. Snowmelt keeps it cold into July, which means the prime window stretches further here than on the lower Gave — a Pyrenean river that looks like the postcard and fishes like one.

  • Mixed
Water quality (WFD)
  • EcologyGood
  • ChemicalUnknown

WFD classification · FRFR256A

The full read · show the working · for brown trout · confidence 80%
How the 31 is built — score × weight = contribution
Temperature32 × 28%9.0
Flow60 × 22%13.2
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity55 × 12%6.6
Conditions total= 57
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
Related guides
Booking & contacts