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.



