The data provided on this site is for informational purposes only.
Absolutely no accuracy or completeness guarantee is implied or intended. The designations employed and the presentation of material on this map do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.
These maps are for demonstration purposes only. The maps use freshwater migratory species ranges derived from the IUCN red list database (IUCN, 2020). These data were filtered for migratory species based on a list of 907 known migratory species. Species were selected if their ranges were coded as extant and possibly extant, and origin native and reintroduced resulting in a total of 665 species. For some species, distribution data was not available and thus not included. For example, for North America, no Salmonids are included currently.
Each individual species range was used to clip the Hydrorivers (V1.0) data set ( Lehner and Grill, 2013 ) to obtain all river reaches (mean length = 4.23 km) within that range. Hydrorivers data was used as it is part of the Hydrobasins ( Lehner and Grill, 2013 ) data that is also used in the IUCN freshwater species assessment process. These were then filtered for larger river reaches by selecting only reaches with flow orders above 5 (long term average discharge of ≥ 10 m3/s). For each of those river segments, the total number of species whose ranges overlap with that segment were calculated.
In addition to the analysis for all species, layers were produced showing only endemic species, defined as species whose range are fully within Hydrobasins level 4 (91 species) and threatened species, by selecting threat status (critically endangered, endangered and vulnerable) in the range data (109 species total)
The threat layers include data on large dams from the GOODD (Mulligan et al., 2020) and GrAND (Lehner et al., 2011) datasets. Dam data was obtained from Global dam watch
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These Swimways case studies show river basins where species ranges have been refined by experts and which include other critical components of fish migration, such as marine migration routes e.g. for the European Eel. This means that additional migratory species and migration routes, not picked up by global scale analyses are included here. Our aim is to provide this additional level of detail for all Swimways in the future.
Click on a green basin or area to see more information about freshwater fish migration in that basin or area.
The species layers show the migratory species richness in each case study basin.