Mountain Freestone · Granite · Honshū

Itoshiro River

Mount Choshi and Itoshiro River

The Itoshiro drains the sacred granite massif of Hakusan and is one of the spiritual homes of Japanese mountain-stream fishing — amago and iwana in clear, cold, boulder-strewn water beneath a mountain pilgrims have climbed for a thousand years.

Poor · Rainbow Trout
Cicada (foam semi pattern) · 6-10
Poorlive now
Not the day for it
Low and clear — careful approach country. A morning for the obvious fish only.
90% confidence
What moved it
  • LevelDry recentlyNo gauge reading
  • Water temp22.0°C
  • ClarityClear
Today's fly
CI
Cicada (foam semi pattern)6-10
High-confidence seasonal pick
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp22.0°C
ClarityClear
Weather24°C
WindNW 15 km/h
Pressure1006 hPa
Rain · recent0.0 mm
Rain · ahead8.5 mm

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

Water temperature for Rainbow Trout
Warm — slow
22°C est.ideal 10–18°C
0°14°28°
How to fish it · for Rainbow 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 22°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayPeak at 6pm

Hatch predictions

Today's headline hatch shown — see all 2 active hatches hour by hour 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
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water yet.

Updated 5 hours ago

Through the year
0–3 scale · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Stenopsyche CaddisHatch
2
3
3
2
Cicada (Semi)Hatch
2
2
Large Dark OliveHatch
1
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1

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

Ranked for today
Rainbow Trout fly box
Permits & access
Permit required — see local rules.
  • Local fishery co-operative yugyoken required; spawning closure around 30 September
  • Confirm exact reach and method rules.
What's coming
Plan ahead
5-day outlook
Water here around 22°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
  1. Mount Choshi and Itoshiro River
    Alpine river with mountain backdrop.
  2. Terrain map of the venue
    Terrain map
About this water

The Itoshiro drains the sacred granite massif of Hakusan and is one of the spiritual homes of Japanese mountain-stream fishing — amago and iwana in clear, cold, boulder-strewn water beneath a mountain pilgrims have climbed for a thousand years. Classic keiryu: steep, intimate, and best read with the patience the old tenkara anglers brought to it.

Under the surface

A cold granite river off the pilgrim mountain of Hakusan, all boulder, pocket and plunge pool. Amago and iwana hold in the broken water of a valley that has drawn ascetics for centuries; this is keiryu and tenkara in their heartland.

Wading: Steep swift pockets, plunge pools, remote access

  • River
  • Granite
  • Confined
  • Pocket water
  • Step pool
Conservation note

White-spotted char (iwana) and amago — the Pacific-side red-spotted masu trout — with some stocked rainbow.

The full read · show the working · for Rainbow Trout · confidence 90%
How the 15 is built — score × weight = contribution
Temperature11 × 28%3.1
Flow60 × 22%13.2
Clarity85 × 18%15.3
Feeding Time80 × 13%10.4
Pressure75 × 7%5.3
Insect activity57 × 12%6.8
Limiting factor: Water temperature (22°C) is outside Rainbow Trout's preferred range (10–18°C)= 54
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–18 °C ideal band — would lift the score and ease welfare.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Char late February to April → late September to mid-October

    Honshu/Shikoku/Kyushu keiryu are managed by local fishery co-operatives — a yugyoken (day/annual ticket) is required, and most streams close around 30 September / mid-October for spawning. Species are surfaced in prose only (no engine slugs for yamame, amago or iwana). Legal status: guidance_not_permission.

Related guides
Euro Nymphingsubsurface methods
Booking & contacts