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illustration: fish swim through the fishpassage The waterways of Waterboard Hoogheemraadschap De Stichtse Rijnlanden contain many artificial barriers such as dams and weirs.
These barriers restrict migration of native fish, which lead to a decline in fish stock and/or reduced biodiversity.
Therefore, a special fish passage has been designed by Wim de Wit, employee of our Waterboard, to solve this problem.

Efficient solution

The original 'De Wit' fishpassage consists of a metal box, divided into several compartments which are interconnected by windows. The windows are staggered to create low-water-velocity areas to allow swimming fish to rest.

All windows have equal dimensions and are below the surface to maintain a constant watervelocity. The bottom is covered by gravel which provides a rough surface that reduces the water velocity over the ramp and can be used by benthic fish and other animals.

The main advantages are that:

it requires little water the compact design can be used in urban and rural areas and it functions in small watercourses. in addition the construction is relatively cheap

A fishing survey confirmed that large numbers of several species of fish and of different length-classes are able to pass the 'De Wit' fishpassages.
For optimal functioning, the watervelocity must be kept below 1 m per second. The number of compartments (up to 24) does not affect its function.

Several 'De Wit' fishpassages have been introduced in our waterways.
Nowadays it is one of the most popular fish passages in the Netherlands.

Learn more

Poster with information and graphics (1,4 Mb) (pdf, 1.4 MB)


Call or e-mail Wim de Wit: wit.wgj@hdsr.nl or +31 30 634 58 41.