Freestone · Granite · Southern Finland / Loviisa (Pernaja), FI

Koskenkylänjoki (Pernajanjoki)

Koskenkylänjoki (Pernajanjoki) terrain map
Tomorrow · About as good as it gets
Ally's Shrimp style
Forecast · Tomorrow
About as good as it gets
On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
90% projected
Today's fly
Ally's Shrimp style
Ally's Shrimp style
Conditions on the water · Tomorrow
Estimate
Level
Dry recently
No gauge reading
Water temp7.7°C
ClarityClearing
Weather9°C
WindN 11 km/h
Pressure1039 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

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

Water temperature for Grayling
Ideal
8°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Midday window — grayling feed best from late morning into early afternoon.
Where
Work runs and glides — grayling shoal in the bottom third of the water column.
Method
Tight-line nymph the bottom third with weighted patterns.
Kit
10 ft #3 rod, floating line, long leader to 4 lb fluoro for nymphs.
Why this works
Excellent — water temperature is right today, though insect activity could be better.
Likely species
Caddisflies
Gammarids
Hatch timeline · tomorrowPeak at 11:00

12:00(now) — Autumn Needle Fly

Stage: Creeping nymphsApproach: Heavy nymphActivity: 46%
Also:Black Midge44%Autumn Olive31%
Peak emergence windowWeather boost6 food groups active

Peak activity at 11:00 — Autumn Needle Fly (Autumn Needle Fly, Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

Supporters see the full sub-surface read.

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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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Evidence
Survey-backed · regionalHigh confidence

Backed by regional invertebrate surveys; no sampling on this exact reach yet.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
1
Grayling seasonSeason
2
2
1
1
2
2
2
2
2
2
Nordic SpringflyHatch
2
3
3
2
Ladoga CaddisHatch
2
3
2
Arctic Cased CaddisHatch
2
3
3
3
2
Large Summer DunHatch
2
3
2

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

Ranked for today
Fly box · Grayling
Small Perdigón
Small Perdigón
Hook 14–18 · Fly
in season · matches water height
Permits & access
Permit required — see local rules.
  • Calendar permit + river permit
  • Porvoo area access.
What's coming
Plan ahead
5-day outlook
Other water nearby · 4
Sipoonjoenpuro
39 km
81
Brown trout · Grayling
Lake Tuusula
49 km
Brown trout · Pike
Kymijoki
55 km
92
Brown trout · Salmon · Sea trout
Vantaanjoki
59 km
Brown trout · Pike
The full read · show the working · for Grayling · confidence 90%
How the 80 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow60 × 22%13.2
Clarity85 × 18%15.3
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity59 × 12%7.1
Conditions total= 80
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 May → 30 September
  • Grayling 1 June → 31 March

    Finnish inland grayling (harjus) rule south of 67°N: closed 1 April – 31 May. Open 1 June – 31 March. Grayling is fully protected in sea areas. Minimum size typically 30-35 cm depending on water. Check Metsähallitus (state waters) or local fishing association permit.

    Closed in spring for spawning.

    Prime sport 1 August → 30 November

Sea trout: Variable seasonal (2026) — East-coast river near Porvoo. Occasional sea trout from the Baltic but not a primary sea-trout destination. Stocks fragile; local guidance required for timing.

Related guides
Grayling Playbookgrayling tacticsEuro Nymphingsubsurface methods
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