The Lab

Development

Every release, logged — newest at the top.

v1.4

Water and fish

Current October 2026

The lake and species pages now show which fish you find more often in turbid or clear water, and in hard or soft water. The Zwarte Meer has its own page, with its food chain drawn. And every account gets 14 days of everything in Specialist, with no credit card.

Beside the lake map: how often surveys catch a fish species in water with more or fewer algae, more or less turbidity or salt. The blue line is this lake.
Beside the lake map: how often surveys catch a fish species in water with more or fewer algae, more or less turbidity or salt. The blue line is this lake.
At the top of the forecast: this month's species, with today's best time and the chance of a big one. Strong models only.
At the top of the forecast: this month's species, with today's best time and the chance of a big one. Strong models only.
All 36 VISparels on and under the map: town waters that are easy to fish, with the fish you can expect there.
All 36 VISparels on and under the map: town waters that are easy to fish, with the fish you can expect there.
The food chain of the Zwarte Meer. Every step was found in the lake itself, with the number of samples beside it, and every arrow has a source.
The food chain of the Zwarte Meer. Every step was found in the lake itself, with the number of samples beside it, and every arrow has a source.
New to VisScanner? Then you get 14 days of everything in Specialist, with no credit card.
New to VisScanner? Then you get 14 days of everything in Specialist, with no credit card.

Water and fish

  • Beside the maps of the IJsselmeer and the Zwarte Meer sit curves: how often surveys catch a fish species in water with more or fewer algae and turbidity, nutrients, salt, calcium, oxygen and organic matter. A blue line shows where that lake sits.
  • The same curves sit in the profile on the species pages. At this release there are 38, for 26 species. A solid curve also passed the strictest checks; a dashed one is less certain.
  • A curve is only shown if it also holds in regions the model had never seen; the model as a whole also held up in later years and in a second dataset. How we tested that, and what did not hold up.

Lakes

  • The Zwarte Meer has its own page.
  • The lake pages draw the lake's food chain: from the smallest life in the water up to fish and predator. Every step was found in the lake itself and every arrow has a source.
  • The tabs now count only what was found inside the lake's outline.
  • Plants, invertebrates and micro-organisms carry checked common names: Dutch ones from the Dutch Species Register, English and German ones from GBIF. Where a family has no common name, the card usually says what kind of organism it is.
  • Depth maps come with Specialist. The IJsselmeer depth map stays free for everyone.

Free trial

  • Every account gets 14 days of everything in Specialist, once. You enter no credit card and nothing is charged. Afterwards you simply keep what you had.
  • On a free account you can invite friends with your own link. For every friend who creates an account and comes back on a later day, you get 30 days of Explorer, up to six times.

Fishing forecast

  • At the top of the forecast are the species that are clearly above their own yearly average this month, with today's best time and the chance of a big one. The figures come from strong models only.
  • In the tables for the next 48 hours the best hours are outlined. Top pick marks the hours of the species at the top. A dashed outline marks hours where the model sees an advantage but there are too few reports to check it.
  • Every hour says how that species' month compares with the rest of its year, so a good hour in a quiet month does not read as a good day to go.

Also

  • All 36 VISparels are on and under the map: town waters that are easy to fish, mainly for young anglers, with the fish you can expect there where we know them, and whether you fish there without lead.
  • An in-depth page for the wels catfish, with the biggest ever caught.
v1.3

Open Data and Permission

Released September 2026

We took every catch dataset with a non-commercial licence out of the models and off the site, and rebuilt the models on open data from Rijkswaterstaat, the water boards and ICES. And with permission from Sportvisunie, the fishing forecast is back: built on the catch reports from mijnvismaat.nl, and free for every angler.

The best hours of the next 48 hours, per species, against an average hour. The pattern moves with sunrise and sunset. Free, from the catch reports on mijnvismaat.nl.
The best hours of the next 48 hours, per species, against an average hour. The pattern moves with sunrise and sunset. Free, from the catch reports on mijnvismaat.nl.
The fishing year: every species' season, with its closed season drawn in. Hatched is closed; grey means fishing is allowed, but every fish goes back.
The fishing year: every species' season, with its closed season drawn in. Hatched is closed; grey means fishing is allowed, but every fish goes back.
The season chart on the species page, here for pike. April and May are closed season: the low values there are the law, not the fish.
The season chart on the species page, here for pike. April and May are closed season: the low values there are the law, not the fish.
The biggest pike ever caught, to scale: from the minimum size to the longest pike on an official record list.
The biggest pike ever caught, to scale: from the minimum size to the longest pike on an official record list.

Only data we may use

  • Three catch datasets carry a non-commercial licence (CC BY-NC): Vangstenregistratie.nl, RAVON and Observation.org. A site with paid plans may not build on them. So we took them out of every model and off every page, before anyone asked us to.
  • What depended on them was paused: the daily catch score, the 7-day forecast, the hourly forecast and the season charts. On the pricing page a paused feature is shown as paused, never as something you buy.
  • We still cite the paused datasets. Their data was obtained, and attribution is owed regardless (sources).

Two new open sources

  • LEW, the national water-quality survey: the fish monitoring by Rijkswaterstaat and every Dutch water board, 2011 to 2023, with the length of every measured fish. Open data, through the Waterkwaliteitsportaal.
  • DATRAS from ICES: the international North Sea trawl surveys, with lengths per haul, going back to 1965. Sea fish now rest on far more than scattered reports.

The models, rebuilt

  • Best spots and the XXL spots run on new models. The old one turned out to measure mostly where the most surveying happens. A species only gets a model score if it beats chance measurably. Otherwise we rank on catch records, and the list says which of the two you are looking at.
  • The habitat model was mostly working out whether water is salt or fresh. It now tells habitats apart within fresh water and within salt water. The bitterling, which spawns only inside a living freshwater mussel, now has the mussel in its model. Before, it was missing entirely.
  • The text on what the models look at has been rewritten for every species, with a photo for the main factors. Every night we check that the text still matches the model it describes.

The fishing forecast is back, and free

  • Sportvisunie has given us permission to build forecasts on the catch reports from mijnvismaat.nl. The condition: they are free for every angler. They are, on every plan.
  • The forecast page shows the best hours of the next 48 hours, and by the hour the chance that a fish you catch is a big one. At this release 22 species have an hourly model and 8 a size model. A species appears in the months its model was tested in. Each species is labelled as a strong or a weak model.
  • The fishing year and the season chart on the species pages are back for 25 species, with the closed season drawn in. Sportvisunie asked for that.
  • The daily catch score and the 7-day forecast stay paused. In these reports we find no day-to-day weather effect that holds up, except for one species. That is too little to publish.
  • Every forecast names its source. We never show individual reports.

On the species pages

  • Catch and release: every species page has been checked against the law, the VISpas conditions and the sea rules. If a fish must go back, the page says so, whoever sets the rule.
  • The biggest ever caught: for pike, zander, sea bass and carp, the Dutch record, the world record and the longest fish on every list we found, drawn to scale.
  • In-depth pages for pike, sea bass, zander and carp: identification, behaviour, tackle and the rules.
  • A padlock now only sits over something that actually exists. A section with nothing in it is left out, for everyone.

Also

  • The first partners are on the map: Hengelsport De Fuik in Leeuwarden and Outdoorpark Friesland.
  • The about page now shows how much data stands behind each species, and how we handle biased catch data.
  • New in the Lab: a day out with ATKB, on how the net decides what you see.
v1.2

The Rebuilt Forecast

Released September 2026

The forecast page has been rebuilt on ground that holds: per species, per day, as a percentage above or below a normal day that month. Wind, moon phase and air pressure are gone. Not because they did not fit, but because they did not earn their place. Plus a new big-fish atlas, language in the URL, and a noticeably faster site.

Every species against its own annual average. Where a card says there is no day-to-day difference, we could not measure a reliable one, and we say so.
Every species against its own annual average. Where a card says there is no day-to-day difference, we could not measure a reliable one, and we say so.
Every species for the week in one table, with the weather above it. Most rows running flat is the point: for those species we measure no day-to-day difference of their own.
Every species for the week in one table, with the weather above it. Most rows running flat is the point: for those species we measure no day-to-day difference of their own.
Big fish per water rather than per grid cell. What counts as big is derived per species from the national length distribution, following the Gabelhouse quality-length convention from fisheries science, not a round number we picked. Specialist
Big fish per water rather than per grid cell. What counts as big is derived per species from the national length distribution, following the Gabelhouse quality-length convention from fisheries science, not a round number we picked.
The fishing year per species, corrected for how much fishing actually happens each month. A quiet month means quiet fish, not quiet anglers.
The fishing year per species, corrected for how much fishing actually happens each month. A quiet month means quiet fish, not quiet anglers.

The forecast, rebuilt

  • Per species, per day: how many percent above or below a normal day in that month. The 0-to-100 score is gone, because it implied a precision that was never measured.
  • The series is monotonic: a day the model rates higher never shows a lower percentage than one it rates lower.
  • Only species with demonstrable day-to-day skill get a daily strip. For the rest we show what does hold up: the season.

What we took out

  • Wind was by far the largest factor in the old model. It turned out to be the shape of the coastline rather than the weather. We wrote up how we found it and what it cost us.
  • Moon phase as timing, air pressure as a feeding switch, water level as height above datum: all three failed against our own data.
  • What survived carries the model: when in the year you fish, and then water temperature. In that order.

Season per species

  • A monthly index per species, corrected for how much fishing happened that month at all. Without that correction every species is a summer species, simply because August reports over four times as much as January.
  • The seasonal charts were computing from survey data rather than angler catches. Fixed.
  • Closed season and naming for eel reviewed and corrected.

Big fish, measured again

  • Big-fish analysis now works per water rather than per grid cell. A canal and a city pond in the same cell are not the same place.
  • What counts as big is derived per species from the national length distribution rather than picked as a round number. That follows the Gabelhouse quality-length convention from fisheries science, anchored against the published values where they exist.
  • Every species is re-tested each night: against shuffled data to expose patterns that are only clustering, and against itself split in half to see whether the result reproduces. Only species that pass get a claim.
  • Hundreds of thousands of length measurements from survey work added, which had been lost at import.

Language in the URL

  • Dutch sits on the plain URL, English and German under /en/ and /de/. Every page now has its own shareable link per language, instead of a language choice that existed only inside your own browser.

Under the hood

  • Three independent data checks run every night: is the data fresh, did each source actually write anything, and is any month far below its seasonal normal. A silent two-month outage is what put us onto this.
  • Critical CSS is now inlined up front, so the first paint no longer waits on a stylesheet.
  • An interrupted sign-in now lands on a page in your own language instead of an error.
  • Every public page can also be requested as plain markdown, for anyone reading the site through a language model.
v1.1

Lakes & Depth Maps

Released July 2026

Every named Dutch lake gets its own page — with all organisms, rarity, a depth map and the sharpest aerial imagery. Plus a 48-hour hourly forecast that shows, per species, when the fish bite, and a spot analysis that honestly shows how over-represented each organism is at a location.

Every named lake its own page: species, water quality and the food web of that specific water.
Every named lake its own page: species, water quality and the food web of that specific water.
Aerial imagery as a map layer — zoom right in on any bank, sharper than the standard map. Explorer
Aerial imagery as a map layer — zoom right in on any bank, sharper than the standard map.
48-hour catch outlook per species — colour shows the hourly chance, weather combined with each species' active window (day, dusk, night). Pikeperch and eel light up at night. Explorer
48-hour catch outlook per species — colour shows the hourly chance, weather combined with each species' active window (day, dusk, night). Pikeperch and eel light up at night.
In 'why this is a good spot', every organism factor shows how over-represented it is here — as a percentage of a typical water (100% = normal), corrected for how much each spot was surveyed.
In 'why this is a good spot', every organism factor shows how over-represented it is here — as a percentage of a typical water (100% = normal), corrected for how much each spot was surveyed.
Expanded, you see the strength, the trend over time and the model weight side by side — spatial and temporal signal kept cleanly apart.
Expanded, you see the strength, the trend over time and the model weight side by side — spatial and temporal signal kept cleanly apart.

Lake pages

  • A dedicated page per named lake, with map, fish species, water quality and the food web of that specific water.
  • Every recorded organism per lake — fish, aquatic plants, insects, molluscs — not just the familiar target species.
  • Rarity classification on every species and organism card, based on how often something is recorded nationally.

Depth maps & structure

  • Per-lake depth maps wherever reliable bathymetry exists, labelled 'surveyed' or 'modelled'.
  • Structure layers that reveal drop-offs, channel edges and shallows — the places fish hold.

Satellite imagery

  • The sharpest aerial imagery available as a map layer, served same-origin so it loads everywhere.

Hourly forecast

  • 48-hour hourly forecast per species (Explorer and up): a heatmap showing how promising each fish is by the hour — weather combined with the species' natural active window (day, dusk or night).
  • So you can watch pikeperch and eel peak at different hours — the temporal patterns from our moon research, now readable hour by hour.

Spot analysis

  • In 'why this is a good spot', every organism factor now shows how strongly it is over-represented here — as a percentage of a typical water (100% = normal), corrected for how much each spot was surveyed.
  • Strength, the trend over time and the model weight are shown separately, so spatial and temporal signal don't blur together. Worded neutrally: co-occurrence points to suitable habitat — more is not automatically better.

Under the hood

  • A food-web story per lake, generated from that water's own co-occurrence signal rather than boilerplate text.
  • Expanded structured data and hreflang (NL/EN/DE); all lake pages added to the sitemap.
v1.0

First Cast

Released March 2026

VisScanner went live: a data-driven fishing map for the whole of the Netherlands, built on open data and models validated on unseen data.

The best spots per species, ranked by where you catch the most — nationwide, from canal to city pond. Explorer
The best spots per species, ranked by where you catch the most — nationwide, from canal to city pond.
Why a spot is suitable: the per-species habitat score, plus the organisms that predict the habitat. Explorer
Why a spot is suitable: the per-species habitat score, plus the organisms that predict the habitat.
Trophy spots: where a species grows larger than average. Specialist
Trophy spots: where a species grows larger than average.
7-day forecast: which day — and which species — gives you the best odds. Explorer
7-day forecast: which day — and which species — gives you the best odds.
The models
Catch model gradient boosting

Predicts how promising a day is from weather, water level, wind and season. Trained across all species and the engine behind the 7-day forecast. The data itself showed water level and wind dominate — not the moon.

Habitat model gradient boosting · trained per species

Estimates per grid cell how suitable the habitat is for a species, from water quality, prey and surroundings. Each model is validated on cells it has never seen (ROC-AUC).

Spot model precomputed

Ranks the best spots per species by combining catch data and habitat scores. Computed nightly so the map stays instant.

Size model random forest · trained per species

Predicts where a species grows larger than average — the trophy spots — from length measurements and the local conditions that drive growth.

The map

  • Interactive fishing map with the best spots based on catch data and habitat models.
  • Trophy spots and catch hotspots per species.

Species

  • Species pages with season, regulations, distribution and statistics for over 250 species.

Prediction

  • 7-day fishing forecast based on weather forecasts, fed by the general catch model.

Ecosystem & water

  • Ecosystem explorer with Shannon diversity, sampling coverage and how often blue-green algae turned up in past surveys.
  • Water quality (Rijkswaterstaat), weather (KNMI/Open-Meteo) and biodiversity (GBIF).

Platform

  • Three languages (Dutch, English, German) and subscription tiers (Free, Explorer, Specialist).