A fishing map that shows the best parts of a lake

nappa rates every part of Finland’s lakes and rivers for seven fish species, hour by hour. The map shows where to go today and how sure each rating is.

Ask for a test invite

contact@willemaki.com

The app is in private testing.

Photo: yrjö jyske, CC BY 4.0, Wikimedia Commons. In the window: nappa's map, Lietvesi.Photo: yrjö jyske, CC BY 4.0, Wikimedia Commons. In the window: nappa's map, Lietvesi.

A misty lake at dusk, reeds and trees on the right. A slim stepped window is cut into the water and shows nappa's map — Photo: yrjö jyske, CC BY 4.0, Wikimedia Commons. In the window: nappa's map, Lietvesi.Photo: yrjö jyske, CC BY 4.0, Wikimedia Commons. In the window: nappa's map, Lietvesi.

On a big lake it’s hard to know where to start

nappa shows which bays and points suit your fish best today, so you can pick a spot before the boat is in the water.

How the map works

Iso-ViilioPieni-ViilioLietvesiKaarteeSammalniemiJärvelä

Iso-ViilioPieni-ViilioLietvesi

1–6

500 m

61.535 N 27.987 Eabout 6 m, guessed

Lietvesi

Iso-Viilio

Top 2 %here in autumn · pike

Great at 19:0018:00–21:00

How sure: High

pike map tested well
weeds beside deeper water

Local rules apply. Check kalastusrajoitus.fi.

Open the spotSaveLog

When

HourGreat at 19:00

The map recolours for the hour you pick.

Fish and colours
Choose one fish or all seven at once. The colour of a square tells you whether that spot is in the top 40, 15, 5 or 2 % of all water in Finland.
Day and hour
When you choose another hour or day, the colours change with it, so you can compare the evening with the morning.
The spot card
Tap a spot to see its rank and best time of day. The card also shows how sure the rating is, what it’s based on, and the local fishing rules.

Shown: Lietvesi, all fish. The hour panel and the card are examples.

Features

Seven species

Pike, perch, zander, trout, burbot, whitefish and bream, together on one map or one at a time.

PikePerchZanderTroutBurbotWhitefishBream

Best spots nearby

A list of the top-rated water within 25 km of the middle of the map, highest first.

HietajärviTop 3 %18 km
RuunasaarenselkäPihlajavesiTop 3 %22 km
HuuhkaalanselkäSaimaaTop 3 %17 km
HietasaarenselkäSaimaaTop 3 %24 km
LuonteriSaimaaTop 5 %4.8 km
LehmäinselkäSaimaaTop 5 %8.4 km
RuokovesiSaimaaTop 5 %11 km
KukkeistenselkäPihlajavesiTop 5 %13 km

Depth and bottom shape

Rocks, shoals, pockets and humps are on the map. Where the depth is estimated rather than measured, it’s marked “guessed”.

Depth contours of Lietvesi on the map; one area dotted, a guess

guessed

Rivers

Rivers are rated for trout and perch, but the trout ratings haven’t been tested yet. On the map, rivers are shown in a single tone.

The Lieksanjoki river at Ruunaa on nappa’s map: the river as cells, land pale, places named in italic — Lieksanjoki, Ruunaa. Trout, not tested yet.

How sure, for every spot

Every spot shows how sure its rating is (Low, Medium or High) and what the rating is based on.

Works offline

If you save an area to your phone before you go, the map keeps working on the water without a signal.

Saved

Test results

I checked the map against fish records that weren’t used to build it. For each record I looked at whether it came from the fifth of its lake that the map rates highest. If the map were guessing at random, that would happen for one record in five.

Pike
about 51 %
Pike records landed in the top-rated fifth about 2.5 times as often as chance would give.
Zander and bream
about 28 %
A smaller lead over chance, about 1.4 times.
Perch, burbot, whitefish
near chance
For these species the map doesn’t beat chance yet.
Trout
not tested

Some of the weak results come from the records themselves, because many of them give only a rough area rather than the exact spot.

The map is built from open data: SYKE and Traficom (depth, not for navigation), Kalastusrajoituspalvelu (rules), FMI and Open-Meteo (weather), Maanmittauslaitos (place names), OpenStreetMap.

Background

On 20 September 2026 a 110 cm pike came up on Lietvesi. After that I wanted to know which parts of a lake hold fish, and whether you can know that before you go, so I started building this map.