Tomasz Mikołajczyk, Przemysław Nawrocki
ABSTRACT. This article is a review of the world literature focusing on the problem of dam reservoirs as barriers to the migration of migratory fish (primarily salmon and trout smolts) during downstream migrations to oceans. While the topic of inhibiting or blocking upstream spawning migrations is widely discussed, the destructive impact dam reservoirs have on downstream migration appears to not have garnered equal attention. Among the many factors impacting fish migratory behavior and fish survival during migration through dam reservoirs, three of the most important were selected for review. The first is delayed migration stemming from disorientation or, in extreme cases, the abandonment of further migration after exiting reservoir basins. The second threat is predation by fish inhabiting reservoirs that are alien to river environments. The third is predation by birds that find ideal habitat conditions on the shores of dam reservoirs. All three of these elements mean that not only the dam but the reservoir, too, present very serious, real threats to the existence of populations of migratory fish species in given rivers.
Key words: dam reservoir, downstream migration, smolt, predation
Przyjęto po recenzji 28.09.2018 r.