Projects

We outline four completed projects:

• Glass eel research and monitoring 2021 for the national monitoring network along the Dutch coast

  In 2021, 15 locations were examined and a total of more than 71,000 glass eels were caught. The season got off to a slow start, probably because the cold persisted for a long time. The sluices were less popular this year. Compared to previous years, we noticed more glass eels, more than 24,500. In total, more than 3100 of these were recovered. The special thing about this year was that we caught back 3 young nematodes from last year with ELFI. Various glass eels have also been seen in other locations. A wonderful result with which we learn a lot about the behavior and distribution of glass eels.
  .

• The attraction eels to of waste-water treatment plants.

We have investigated the effect of effluent on the migration of eels. ELFI revealed that effluent has a strong attractive effect on eels at some locations.

• Migration in a new fish passage (Marrum).

The ELFI demonstrated the use of the fish passage by elvers. Mark-recapture (VIE tags) revealed that there could be a considerable period between arrival and use of the passage. Follow-up monitoring took place in 2020.

• Comparative research between the dip net and ELFI for the Dutch Ministry of Agriculture, Nature and Food Quality (LNV).

Wageningen Marine Research (WMR) carries out national monitoring of elvers with dip nets. In addition, a three-year comparative study is being conducted between the dip net and ELFI. Mark-recapture methods are also being used, by means of VIE tags, to gain insight into the barrier effects of structures (locks, pumping stations, dams). Results are published in ICES WGEEL (Working Group on Eels). 

ELFI research sites

The map below shows the locations where ELFI research in 2020 has been carried to date.

ELFI has now been deployed more than 60 times for a period of at least three months, in both salt and freshwater. At some locations, monitoring was carried out for several years in a row or with several ELFIs simultaneously.