Brook fish and water quality
Brooks in the Netherlands currently contain far fewer species of fish than they could do.
Trends
Most of the brooks in the Netherlands are in the hillier parts of Limburg and on the higher sandy areas in the centre and east of the country. In hardly any of the brook catchments do the number of fish species exceed 75% of the potential. Species numbers are particularly low in the north and east. On average, the situation is slightly better in the south, though here too there are fewer fish species than could be expected.
Many fish species have declined because of worsening water quality and the canalisation and straightening of the brooks. The engineering has changed the cross-section by creating steep banks. Only about 4% of brooks retain their pristine form, and the weirs constructed in many brooks act as barriers to fish.
In recent years there has been renewed attention for restoring the meanders and pristine profile of brooks. And in many locations fish passages have been installed, so that migratory fish can bypass weirs and other obstacles. After fish passages were installed in the Regge, certain fish species returned; they included the silver orfe and chub.
Technical note
The Ministry of Agriculture, Nature Management and Fisheries has designated various target fish species in its nature conservation policy. These are species that are of international importance and/or are endangered in the Netherlands. The map shows the catchments of brooks and the percentage of target species found per catchment. In total, 17 species have been designated as target species. Of these, 12 are for sluggish brooks and 12 for fast-flowing brooks (see table). Fast-flowing brooks are commonest in the hillier parts and in the Achterhoek; the sluggish brooks occur in the rest of the country.
The data on the distribution of fish species are taken from the database of the Natuurhistorisch Genootschap Limburg for 2001, the database of De Nie's fish atlas (1996) and STOWA's "Database Limnodata Neerlandica" (2001).
References
- Bal, D., H.M. Beije, M. Fellinger, R. Haveman, A.J.F.M. van Opstal en F.J. van Zadelhoff (2001). Handboek Natuurdoeltypen. Tweede, geheel herziene editie. Rapport Expertisecentrum LNV nr 2001/020, Ministerie van Landbouw, natuurbeheer en visserij, Wageningen.
- Higler, L.W.G., H.M. Beije en W. van der Hoek (1995). Stromen in het landschap; ecosysteemvisie beken en beekdalen. IBN-DLO. Wageningen.
