Freestone · Sedimentary · Shikoku, JP

Shimanto River

Spring in Shimanto River

The Shimanto is called Japan's last clear river — a long, undammed, gently flowing water through rural Kōchi crossed by its famous low 'sinking bridges', where ayu and amago share the river with a way of life that has changed little.

Today · Slow going — pick your moments
Sculpin Streamer
Forecast · Today
Slow going — pick your moments
Slow going — pick your moments and do not force it.
45% projected
Today's fly
Sculpin Streamer
Sculpin Streamer
Conditions on the water · Today
Estimate
Level
Light rain recently
No gauge reading
Water temp10.9°C
ClarityVery coloured
Weather21°C
WindN 14 km/h
Pressure1009 hPa
Rain · recent8.6 mm
Rain · ahead0.0 mm

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

Water temperature for Amago
Ideal
11°C est.ideal 9–17°C
0°14°28°
How to fish it · for Amago
When
Spring to the autumn closure (salmonids in the upper river)
Where
The Shimanto is called Japan's last clear river — a long, undammed, gently flowing water through rural Kōchi crossed by its famous low 'sinking bridges',…
Why this works
Excellent — water temperature is right today, though time of day could be better.
Hatch timeline · todayPeak at 6am

12pm(now) — Black Gnat

Stage: On emergersApproach: Emerger or dryActivity: 28%
Also:Autumn Olive25%
Peak emergence window8 food groups active

Peak activity at 6am — Kajika Sculpin (Japan) (Kajika Sculpin (Japan), 5 food groups active)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 3 as a supporter.

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Evidence
Records-basedModerate confidence

Based on species-occurrence records, not local invertebrate surveys.

Through the year
0–3 scale · October highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Stenopsyche CaddisHatch
2
3
3
2
Cicada (Semi)Hatch
2
2
Ephemera strigata (Mid-Reach Keiryu Mayfly)Hatch
2
3
3
3
2
Epeorus latifolium (Riffle Mayfly)Hatch
2
3
3
3
3
3
2

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

Ranked for today
Amago fly box
EH
Elk Hair / Stenopsyche caddis
12–14 · Sedge
Evening sedge — twitch or dead-drift it as the light goes.
CB
Cicada & beetle terrestrials (midsummer)
10–12 · Terrestrial
Fish it tight to the bank on warm, breezy days.
Permits & access
Permit required — see local rules.
  • Co-operative yugyoken required; ayu and salmonid rules differ; spawning closure in autumn
  • Confirm the exact reach.
What's coming
Plan ahead
5-day outlook
Other water nearby · 1
Gallery · 2
  1. Spring in Shimanto River
    Japan's longest free-flowing river.
  2. Terrain map of the venue
    Terrain map
About this water

The Shimanto is called Japan's last clear river — a long, undammed, gently flowing water through rural Kōchi crossed by its famous low 'sinking bridges', where ayu and amago share the river with a way of life that has changed little. Broad, slow, pastoral fishing in a valley that feels like an older Japan.

Under the surface

Japan's 'last clear river' — long, largely undammed, sliding through rural Kōchi past the low chinkabashi sinking-bridges. Amago and iwana hold in the upper reaches; ayu and an old river culture fill the lower. Broad, gentle, pastoral water.

Wading: Gentle but broad water, soft banks

  • River
  • Sedimentary
  • Unconfined
  • Pool riffle
  • Glide
Conservation note

White-spotted char (iwana) and amago in the upper reaches (ayu in the lower river).

The full read · show the working · for Amago · confidence 90%
How the 80 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow60 × 22%13.2
Clarity95 × 18%17.1
Feeding Time60 × 13%7.8
Pressure80 × 7%5.6
Insect activity67 × 12%8.0
Conditions total= 80
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
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
Booking & contacts