By Kerry Brink
Many freshwater fish species around the world need to migrate for their survival. During their journey they often encounter man-made barriers, such as dams and weirs, which impede their migrations upstream or downstream of barriers. A well known solution to this problem, is the construction of a fishway that allows fish to pass a physical obstacle. From as early as the 18th century, fishways have been implemented. Over the decennia since then, knowledge, technology and experience have developed substantially, resulting in many different fishway designs specific for different regions or fish species. This can vary from a nature-like fishway to a lock fishway (see above figure, taken out of the From Sea to Source 2.0 book). In the From Sea to Source 2.0 book there are various examples of fishways and fishway designs.
Along with the many new insights into fishway effectiveness and efficiency, there is more evidence to suggest that fishways are not the ultimate solution to fish passage. In some cases the presence of a fishway has been shown to impact fish populations, as was shown by Pompeu and his colleagues in Brazil (Pompeu et al., 2011). In other cases, the post-construction management and maintenance is often neglected, particularly in developing countries, which not only leads to severe gaps in important information about the performance of fishways, but also hampers the advantages that the fishways provide.
From more information, see the From Sea to Source 2.0 book or the various best practice guidelines from your region. In Europe, the DWA, 2014 guideline (Fischaufstiegsanlagen und fischpassierbare, Bauwerke – Gestaltung, Bemessung, Qualitätssicherung. Merkblatt DWA-M 509, D-Hennef.) and the CEN/TC 230, 2018 guideline (Guidance for assessing the efficiency and related metrics of fish passage solutions using telemetry, version 2.81), both offer comprehensive overviews of fishways.
Fishways drawings (c) From Sea to Source 2.0; Maintenance cartoon (c)Auke Herrema