Mountain Freestone · Granite · Honshū, JP

Kiso River (upper / Kiso Valley)

Kiso River from Mount Igi 2010-02-28
Tomorrow · Not the day for it
Gold-Ribbed Hare's Ear
Forecast · Tomorrow
Not the day for it
Not much stacked in your favour today. Worth an hour if you are nearby, not worth the special trip.
45% projected
Today's fly
Gold-Ribbed Hare's Ear
Gold-Ribbed Hare's Ear
Conditions on the water · Tomorrow
Estimate
Level
Very heavy rain recently
No gauge reading
Water temp15.7°C
ClarityUnfishable
Weather22°C
WindN 4 km/h
Pressure1025 hPa
Rain · recent51.2 mm
Rain · ahead7.8 mm

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

Water temperature for Rainbow Trout
Ideal
16°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
Good — water temperature is working for you, but insect activity is the limiting factor today.
Hatch timeline · tomorrowPeak at 18h

12h(now) — Glossosoma (Japan)

Stage: Taking dunsApproach: Dry flyActivity: 64%
Also:Heather Fly54%Isonychia japonica40%Daddy Long Legs35%
Peak emergence windowWeather boost10 food groups active

Peak activity at 18h — Net-Spinning Caddis (Japan) (Net-Spinning Caddis (Japan), Weather boost)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 3 guilds as a supporter.

Start free trial

14-day free trial. Cancel anytime.

Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Supporters see what else is on the menu.

Start free trial

14-day free trial. Cancel anytime.

Evidence
Records-basedModerate confidence

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

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Ephemera japonica (Upstream Keiryu Mayfly)Hatch
2
3
2
Stenopsyche CaddisHatch
2
3
3
2
Cicada (Semi)Hatch
2
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
Fly box · Rainbow Trout
Permits & access
Permit required — see local rules.
  • Co-operative yugyoken required; spawning closure in autumn
  • Confirm reach and method rules.
What's coming
Plan ahead
5-day outlook
Other water nearby · 1
Azusa River (Kamikōchi)
50 km
20
White spotted char · Yamame · Rainbow trout
Gallery · 2
  1. Kiso River from Mount Igi 2010-02-28
    Central Honshū river.
  2. Terrain map of the venue
    Terrain map
Conservation note

White-spotted char (iwana) and amago, with stocked rainbow in places.

The full read · show the working · for Rainbow Trout · confidence 65%
How the 64 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow41 × 22%9.0
Clarity45 × 18%8.1
Feeding Time70 × 13%9.1
Pressure75 × 7%5.3
Insect activity35 × 12%4.2
Conditions total= 64
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
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