Royal Netherlands Institute for Sea Research
Royal Netherlands
Institute for Sea Research

Wadden Barometer | Fish


Mean daily catch (kg wet mass)

Analysis of kom-fyke catches

Monitoring of the fish fauna dates back to 1959 when NIOZ secured the services of Henk Beumkes, one of the last fishermen from Southern Texel and a specialist in so-called kom-fyke fishing. From 1960 onwards, kom fyke fishing has been carried out at the southern tip of Texel without any changes in methodology. Each spring and autumn the kom-fyke has been installed and emptied on a daily basis during the months April-June and September-October. This has resulted in a long-term data series spanning more than 55 years and consisting of 270,000 records. From the beginning onwards, all individuals were identified and counted.

In 2015, an extensive analysis of the kom-fyke catches was published for the period 1960 - 2012. The main result was a negative trend in the daily catches from 1980 to the present, with a 10-fold decrease in total catch. The average fish mass decreased from about 150 to 20 g wet weight. These changes are most likely the result of the cumulative impact of a combination of factors, such as increased water temperature, habitat destruction in the coastal zone (sand dredging and beach nourishment, fishing), increased predation by top predators, and changes in large-scale hydrodynamic circulation.


Trend in mean fish weight (g)

Data from 2015 did not deviate from the previous few years. Daily catches remained stable at a few kilogrammes per day. With respect to species composition, Butterfish was relatively abundant. A year of successful spawning and recruitment results in catches of adults a few years later; Juveniles are not caught because they slip through the nets. The Butterfish caught in 2015 were 3 years old. There was a remarkable increase in the number of Eels caught in 2015. It will be interesting to see whether this trend will continue in 2016.

2015 was also a good year for the Golden Grey Mullet. They were observed again for the first time since 1990. The fish were 2 to 4 years old and most probably originated from the South of Europe. For the past seven years, Shanny has also appeared in the nets. They normally live between rocks and stones, in this case, at the base of the dykes. Their range seems to be slowly shifting northwards. Since 1985, the catch of Seabass has been at a high level. With the seawater temperatures still increasing, the Seabass, which is adapted to high water temperatures, is becoming increasingly abundant in this region.

Monitoring MSC Zoe plastics

During the night of 1st to 2nd January 2019, during a north-western storm, the container ship MSC Zoe lost at least 345 containers on the shipping route north of the Wadden Islands.

Rijkswaterstaat (RWS) wants research to be carried out into the possible consequences of the container disaster on the ecosystem of the North Sea and Wadden Sea.The objective of this research is to collect plastics and organisms registered in 2019 that may have ingested plastics in conjunction with existing programmes.

the requested investigation includes: 

  • Plastics in fish
    In combination with long-term research on fish in the Marsdiep