Spring Fed · Limestone · Aragón

Ríos Piedra, Mesa and upper Jalón (Calatayud / Monasterio de Piedra)

Monasterio de Piedra venue image
Marginal · Brown Trout
Perdigón · 14-18
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.
90% confidence
What moved it
  • LevelProxyvia Río Abión
  • Water temp18.3°C
  • ClarityClear
Today's fly
Perdigón
Perdigón14-18
High-confidence seasonal pick
Conditions on the water
Proxy gauge
Level
Steady
Proxy
via Río Abión
Water temp18.3°C
ClarityClear
Weather25°C
WindSE 8 km/h
Pressure1017 hPa
Rain · recent0.2 mm
Rain · ahead9.9 mm

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

Water temperature for Brown Trout
Warm — slow
18°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Water at 18.3°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 6 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 4 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 · 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
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
Permits & access
Permit required — see local rules.
  • Aragón fishing licence required; named cotos and free-water sections each carry their own dates, quotas and method rules
  • Trout are only a legitimate target in salmonid-classified reaches — confirm the beat's status before fishing.
What's coming
Plan ahead
5-day outlook
Water here around 18°C. Nothing cooler within range — carry a thermometer.
Gallery · 1
  1. Terrain map of the venue
    Terrain map
The full read · show the working · for Brown Trout · confidence 90%
How the 38 is built — score × weight = contribution
Temperature51 × 28%14.3
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time60 × 13%7.8
Pressure80 × 7%5.6
Insect activity66 × 12%7.9
Conditions total= 70
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Río Abiónproxy
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
Apple MapsGoogle Maps
Seasons & zones
  • Trout check named Aragón coto or free section → check named Aragón coto or free section

    Iberian System tributaries of the Jalón, governed by Aragón's section-based trout rules. The cooler spring-fed reaches and karstic ravines hold the salmonid interest; flows are highly seasonal. Confirm the exact coto/free-water status and 2026 dates per beat.

Related guides
Chalkstream Playbookchalk stream tacticsPyrenees PlaybookSpanish riversEuro Nymphingsubsurface methods
Booking & contacts