Royal Netherlands Institute for Sea Research
Royal Netherlands
Institute for Sea Research
Phone number
+31 (0)222 369 368
  • Laboratory technician
  • Determining and measuring fyke catches
  • Long-term series of fish data
  • Researching patterns in fish stocks
  • Fish and Kom-fyke stories

Hans Witte


Research interests

Ever since I started working as a lab technician at NIOZ in 1972, and later as a research assistant, one of my tasks was to monitor the fyke catches. Up until that point, the fishing company, who had done it for decades, were still operating. The nets were operative from April to November, and the edible fish were sold at the junction on the main road. The fyke was emptied daily by the fishermen and the catch was counted and recorded. Occasionally I went to help, but it took a long time before I was acknowledged as a fully-fledged fisherman.

In the year that I started, director Jenne Zijlstra had the idea of using the fyke data to monitor variations in fish stocks, in order to detect regular patterns, a ‘hot topic’ at the time. Zijlstra hoped to find an explanation for the variations, for example, as a result of regular changes in the warm Gulf Stream. This laid the foundation for a long-term data series, which has now been running for 53 years.

My task is to ensure the quality of the fyke data. This means that the fish have been correctly identified to species level, and that the computer-entry of all data is accurately carried out. To this end, in 1983 I spent a year entering all the old data, and later checking all the entered numbers. Soon I began collecting additional data from the catch. This included length, and every Friday a number of animals were weighed and stripped of some scales and hearing stones for age determination. Nowadays stomach contents and stable isotopes are also recorded to determine the position of the fish in the food chain, thus ensuring that the catches are used as optimally as possible.






Please find my list of publications at the bottom of this webpage. 


Professional education



Awards and Prized





Linked news

Wednesday 22 January 2020
Public lectures by NIOZ scientists at Ecomare
In February and March, 7 NIOZ scientists will give 4 public lectures at Ecomare. The lectures are a run-up to the new exhibition Wonderlijk Wad that will be opened at the beginning of May at Ecomare. The main language is Dutch, tickets cost € 5,-,…

NIOZ publications

Linked projects

Mosselwad: how mussel beds thrive
Jaap van der Meer
Project duration
1 Jul 2009 - 30 Jun 2016
POMVIDDY_Polar marine diversity and dynamics
Corina Brussaard
Netherlands Organization for Scientific Research
Project duration
23 May 2017 - 22 May 2021
Pilotfase vismonitoringfuik in de Zoutkamperlaag
Henk van der Veer
Ministry of Agriculture, Nature and Food Quality
Project duration
4 Dec 2017 - 31 Dec 2020