Reservoir · Mixed · Idaho, US

Island Park Reservoir

Aerial view of Island Park Dam holding back Island Park Reservoir, with the Henrys Fork River flowing out below the spillway
Fair · Rainbow
Balanced Leech · 8-12
Fairlive now
Reasonable autumn fishing likely at Island Park Reservoir
Glassy and bright — hard work without a breeze. Hard work without breeze. Look for the dimples.
56% confidence

Island Park Reservoir is often best in spring through autumn.

What moved it
  • WindN 3 km/hCalm
Today's fly
Balanced Leech
Balanced Leech8-12
Proven pattern for this period
Conditions on the water
Estimate
Wind
Calm
N 3 km/h
N
N
from the north
WaveFlat calm
Water temp9.0°C
Air temp2°C
CloudOvercast
Pressure1021 hPa
Rain · recent0.0 mm

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

How to fish it · for Rainbow
When
Conditions are not ideal but fishable at Island Park Reservoir. Flat calm means fish may be spookier — longer leaders and subtler flies will help.
Where
Start with Balanced Leech (8-12) on a As per local method. Rainbows respond to more active retrieves — try short strips between pauses. If that does not produce, switch depth or speed before changing the pattern entirely.
The plan
Plan A

Start with Balanced Leech (8-12) on a As per local method. Rainbows respond to more active retrieves — try short strips between pauses. If that does not produce, switch depth or speed before changing the pattern entirely.

Plan B

A fry-imitating pattern stripped through the margins can save a blank in autumn.

Watch for

Keep an eye on changing conditions — wind shifts and cloud breaks can trigger short feeding spells.

Bank

Flat calm suits bank fishing near features — points, weed beds, and inflows where fish patrol.

Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 2 as a supporter.

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Through the year
0–3 scale · October highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Gray DrakeHatch
2
2
CallibaetisHatch
2
3
3
3
2
Hexagenia (Western)Hatch
2
2
Black MidgeHatch
2
3
3
3
3
3
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
CH
Chironomid
12-16 · Pattern
Proven pattern for this period
Permits & access
Permit required — see local rules.
  • Idaho stillwater regulations — check Idaho Fish & Game
  • Level swings with irrigation draw.
What's coming
Plan ahead
5-day outlook
Condition match
59%
Cloud50%
Wind65%
Temp60%

A reasonable day here, though cloud isn't quite in the sweet spot.

Fishing better nearby · 5
Henrys Fork
11 km
83
Rainbow trout
Warm River
34 km
70
Rainbow trout · Brook trout
Henrys Lake
29 km
Cutthroat trout · Brook trout
Cliff Lake
41 km
Rainbow trout · Brown trout
Wade Lake
47 km
Rainbow trout · Brown trout
Gallery · 2
  1. Aerial view of Island Park Dam holding back Island Park Reservoir, with the Henrys Fork River flowing out below the spillway
    Island Park Dam and Reservoir on the Henrys Fork
  2. Terrain map of the venue
    Terrain map
Water quality · US Clean Water Act
  • Aquatic life: Not assessed
What this classification means

EPA ATTAINS assessment unit 'Island Park Reservoir' (ID17040202SK020L_0L), 2022 Integrated Report. Aquatic Life use: Not Assessed. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.

Status is for the Clean Water Act assessment unit covering this reach.

EPA ATTAINS (Clean Water Act) · ID17040202SK020L_0L

Why this score
  • autumn conditions with overcast skies and calm wind.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout Saturday de Memorial Day weekend → 30 November
Related guides
Big Stillwater Playbookreservoir tacticsReservoir Entomologymatching the hatchThermal Layers & Troutreading depth and temperature
Booking & contacts