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J Environ Manage. 2017 Dec 15;204(Pt 1):467-471. doi: 10.1016/j.jenvman.2017.09.022. Epub 2017 Sep 15.

30 years of data reveal dramatic increase in abundance of brown trout following the removal of a small hydrodam.

Author information

1
DTU Aqua, Section for Freshwater Fisheries and Ecology, Vejlsøvej 39, 8600 Silkeborg, Denmark. Electronic address: kbir@aqua.dtu.dk.
2
DTU Aqua, Section for Freshwater Fisheries and Ecology, Vejlsøvej 39, 8600 Silkeborg, Denmark; Danish Centre for Wild Salmon, Brusgårdsvej 15, 8960 Randers, Denmark.
3
DTU Aqua, Section for Freshwater Fisheries and Ecology, Vejlsøvej 39, 8600 Silkeborg, Denmark.

Abstract

Humans and freshwater ecosystems have a long history of cohabitation. Today, nearly all major rivers of the world have an in-stream structure which changes water flow, substrate composition, vegetation, and fish assemblage composition. The realization of these effects and their subsequent impacts on population sustainability and conservation has led to a collective effort aimed to find ways to mitigate these impacts. Barrier removal has recently received greater interest as a potential solution to restore river connectivity, and reestablish high quality habitats, suitable for feeding, refuge and spawning of fish. In the present study, we present thirty years of data from electrofishing surveys obtained at two sites, both prior to and following the removal of a small-scale hydropower dam in Central Jutland, Denmark. We demonstrate that the dam removal has led to a dramatic increase in trout density, especially in young of the year. Surprisingly, we found that this increase was not just upstream of the barrier, where the ponded zone previously was, but also downstream of the barrier, despite little changes in habitat in that area. These findings suggest that barrier removal may be the soundest conservation option to reinstate fish population productivity.

KEYWORDS:

Conservation; Dams; Fish passage; Migration; Population; Salmonidae

PMID:
28923580
DOI:
10.1016/j.jenvman.2017.09.022
[Indexed for MEDLINE]

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