Fish-Tales (English)

'Onder water in Leiden' translates as Under water in Leiden.

  • 'Under water in Leiden' is a unique project in the Netherlands, started by locals in 2011. Locals became interested in the life under the surface after the city-canals got cleaner and clearer.
  • This clarity (and growing abundance of wildlife) was mainly due to well-planned maintenance of the waterways within the city and surrounding areas.
  • The project 'Monitoring of Fish', encompasses the checking and counting of wildlife in the canals and is since 2013 an official biodiversity project.

groep-karpers whalewatching
rivierdonderpad leiden danielsiepman
jun2019 10a schildpad geelbuik
onderwaterinleiden meerkoet dood-snoekje
onderwaterinleiden de-doorbraak schildpad nagellak
onderwaterinleiden pike city-canal sunlight
victoria wolhandkrab hoornblad
jul2017 10a toverstokje

Support from local and nationwide institutions

  • Under water in Leiden is supported by the Leiden council, various institutions who work with and on the waterways and of course widely appreciated and cared for by the locals.
  • Almost 50% of the monitoring is done snorkelling in the canals, with a special permit, since swimming in the canals in Leiden is otherwise prohibited.
  • Would you like to join Diving Club Calypso in a snorkelling trip and monitor the fish with the specialists? Send an e-mail to Calypso. Please note: You must be a well-abled snorkeller or diver! There is a disclaimerpage.

Main goals of our project:

  • Two neighbours spotting a pike

    To get a better insight in the abundance of all species of flora and fauna that inhabit the waters of Leiden (30 mins from Amsterdam).
  • Special interest is in how exactly the animals use the canals (for breeding, feeding etc). And we try and uncover what measures are necessary to keep them (or invite even more of them) here.
  • Another goal is to get the people of Leiden involved in taking care of their environment 'in front of their door'.
  • They can do that by taking out debris with small fishing nets, or by helping with the big cleanup-jobs we organize with our free litterfishing canoos. Join us!
  • But also by spotting, counting and registering the fish they see, 'protecting their pike' (each canal has its own individual, territorial pike) and so forth.

Does this inspire other cities?

  • Aaf's independent bureau of advisory work on aquatic species in the canalsAs projectleader of the succesful fishmonitoring group in the Havenwijk, Ms Aaf Verkade has been asked by the council to extend her activities to new communities in Leiden annually since 2015.
  • If possible, we would like our project to be copied by enthousiastic locals in other cities as well! It worked very well with our 'Feline Lifeline' programme, see below.
  • Aaf enjoys stimulating the locals to clean up the waterways in their communities and care for their 'neigbours under water' - you can hire her to give an inspirational speech (in 5 languages).
  • See her professionalwebsite for more information about her work as an independent City Canal advisor (in Dutch only).

Flashlightfishing, just one of 10 methods we use to count fish

Flashlightfishing, just one of 10 methods we use to count fish

Their first American crayfish! (exotic species, though)

Their first American crayfish! (exotic species, though)

Would you believe this photo was taken in a canal?

Would you believe this photo was taken in a canal?

Our canals are full of (young) fish; at least 22 species!

Our canals are full of (young) fish; at least 22 species!

Handpicked media are invited to interview our team

Handpicked media are invited to interview our team

Missisippi slider turtles, at home in Leiden too

Missisippi slider turtles, at home in Leiden too

A bullhead (rivierdonderpad) saved by Nick

A bullhead (rivierdonderpad) saved by Nick

Trashurehunting in the canals, with unbelievable finds!

Trashurehunting in the canals, with unbelievable finds!

Protected species and amazing discoveries

  • Bullheads help us to design the best hotel as they will be relocated in their native habitatThe most precious species found until now are: eel, spined loach and bullhead.
  • Exotic species, like Chinese mitten crabs and American crayfish have also been discovered, as well as Mississippi slider turtles, which are seen abundantly, caught (snorkelling) and photographed and measured for research.
  • The first exotic goby was discovered in 2015 (the tube-nosed goby) and the second (black goby) in 2018. Their invasion of the Leiden canals is being investigated with a 'goby-grant': Aaf won this special grant from Stichting RAVON.
  • Aaf also discovered a 'flat fish' in the research area Havenwijk-Zuid in 2015, called the flounder, which is a species that uses both salt and sweet water to go through all of its life-cycles.

Facebook of big fish

  • Indeed, big fish have (just like dolphins and whales) nicks, scratches and parts of their fins missing, which makes them individually distinguishable.
  • They are catalogued in their own 'Facebook' (Smoelenboek) on this website.

onderwaterinleiden smoelenboek zaklampvissen tekeningen
onderwaterinleiden smoelenboek zeelt z-32 becks
onderwaterinleiden smoelenboek karpers
onderwaterinleiden smoelenboek rivierkreeft
onderwaterinleiden smoelenboek rivierdonderpad
onderwaterinleiden smoelenboek zeelt-
onderwaterinleiden smoelenboek zeelt-

Cleaning up the clutter under water

  • The bikes and other debris on the bottom are regularly taken out of te water with help of volunteer captains of stichting de Leidse Rederij, locals, volunteers from other cities and the council. Click here for a link.

onderwaterinleiden winnaar-fotowedstrijd floorhendriks groot
onderwaterinleiden grofvuilvissen fiets
drijfvuilvissen kanovloot onderwaterinleiden afval
onderwaterinleiden grofvuilvissen haanstra monique-shaw
onderwaterinleiden grofvuilvissen fietsen
onderwaterinleiden grofvuilvissen bewonersparticipatie
onderwaterinleiden grofvuilvissen brandweerduiker happy

Cleaning up the (floating) debris

  • drijfvuilvissen met de kanovloot van Onder water in Leiden, foto (c) Maryse LorangerWe started a Taskforce with the council, a tourboat company (Stichting de Leidse Rederij), a back-to-work rehab programme and locals with the main goal to regularly clean up the plastic garbage floating in the city. This works a treat!
  • Click here for the Dutch page.
  • And here for the English page, which explains how you can use a canoo for free to have an enjoyable time on the water, whilst helping to clean up our environment, where no one else can reach it.

Project of the KNNV, Leiden dept.

  • Since january 2013, the project 'Monitoring of fish in Havenwijk-Zuid' is one of many projects overseen by the KNNV, Leiden dept.
  • The KNNV dept. of Leiden and surrounding areas, click to visit their websiteThis organization of inspired and enthousiastic (amateur) biologists make sure all data is gathered professionally and processed in such a way, that institutions like the council, Angler's Union Leiden and the watercontrol department (Hoogheemraadschap van Rijnland) can use the data to adjust their strategies and plans regarding water treatment and fishing regulations, if necessary. 
  • They even published a book about the art of 'flashlight-fishing' (Zaklampvissen: Dutch only), which seems to be the best method to count the abundance of fish in a city environment.

Feline Lifelines

  • Feline Lifelines is a hugely successful 'save your cat from drowning in the canals' programme.
  • It was started by the locals, with support from the council, in 2009 in the Havenwijk.
  • More information (in English) can be found here.
  • Because of its immense success in Leiden (more than 100 cats saved from drowning) it has expanded to at least 20 more cities in the Netherlands.

onderwaterinleiden katuitdegracht waterdrinken
kug-logo breed
onderwaterinleiden katuitdegracht reddingsnestje
onderwaterinleiden reddingsnestje meerkoetenfamilie
onderwaterinleiden katuitdegracht kattenklimtouwen meerkoetjes
onderwaterinleiden aaf kattenklimtouw-inspectie

Kraakhelder water in Leiden

  • onderwaterinleiden snorkelmonitoring zeelt-
  • onderwaterinleiden snorkelmonitoring visjes schroef
  • onderwaterinleiden vissenmonitoring ravon
  • onderwaterinleiden snorkelmonitoring visjes-huizen
  • onderwaterinleiden onderwater fuut zwemmend
  • onderwaterinleiden snorkelmonitoring visbroed
  • onderwaterinleiden snorkelmonitoring visjes fiets
  • handleiding-afvalmelden leiden
  • onderwaterinleiden snorkelmonitoring doorkijkje
  • onderwaterinleiden onderwater baarzen
  • onderwaterinleiden monitoring onderwater zeelten
  • onderwaterinleiden snorkelmonitoring onder-boot
  • onderwaterinleiden snorkelmonitoring paling

Lees meer over de kwaliteit van het water in de stadsgrachten van Leiden.

Twitter @owinleiden

owinleiden RT @GuidoRijnja: Zou zo graag je dag verlichten met een rake grap of grol, maar wat valt er meer te dichten of gebaren dan: hou vol. #dagdi
owinleiden RT @IVN_Leiden: @owinleiden @zwerfinator @DSiepman @Plastic_spotter Met al die wandelende mensen zou het toch na de Corona helemaal schoon…


"Onder water in Leiden" is onderdeel van "Aaf Verkade Adviseur Stadsgrachten"

Voor interviewverzoeken zie de contactpagina

Kijfgracht 12
2312 RZ Leiden

KvK 64674487
BTW nummer NL163735694B01
NL47 Trio 0391068563 t.a.v. Verkade Stadsgrachten

Disclaimer - Algemene voorwaarden - Privacy


onderwaterinleiden kleurplaat 1mb

Illustrator: Lisa Poot,