Dead-end effect
From BAWiki
Definition
During their upstream migration fish follow the direction of the flow until they meet an obstacle at which point they normally try to seek a path around the obstruction. If they fail to find another path upstream or any other route, this is a migratory dead end.
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Abbreviations
Source
Guideline Upstream Fishways on German Federal Waterways (AH FAA), Bundesanstalt für Wasserbau (BAW) und Bundesanstalt für Gewässerkunde (BfG), Version 2.0, 26/06/2015 (retrieved 10.05.2017)