Fish ladders: safe fish passage or hotspot for predation?
Fish ladders are a strategy for conserving biodiversity, as they can provide connectivity between fragmented habitats and reduce predation on shoals that accumulate immediately below dams. Although the impact of predation downstream of reservoirs has been investigated, especially in juvenile salmoni...
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Sociedade Brasileira de Ictiologia
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doaj-6088cd0a24df412c89abbfd4aab154422020-11-24T20:57:07ZengSociedade Brasileira de IctiologiaNeotropical Ichthyology1982-022410468769610.1590/S1679-62252012000400001S1679-62252012000400001Fish ladders: safe fish passage or hotspot for predation?Angelo Antonio Agostinho0Carlos Sergio Agostinho1Fernando Mayer Pelicice2Elineide Eugênio Marques3Universidade Estadual de MaringáUniversidade Federal do TocantinsUniversidade Federal do TocantinsUniversidade Federal do TocantinsFish ladders are a strategy for conserving biodiversity, as they can provide connectivity between fragmented habitats and reduce predation on shoals that accumulate immediately below dams. Although the impact of predation downstream of reservoirs has been investigated, especially in juvenile salmonids during their downstream movements, nothing is known about predation on Neotropical fish in the attraction and containment areas commonly found in translocation facilities. This study analysed predation in a fish passage system at the Lajeado Dam on the Tocantins River in Brazil. The abundance, distribution, and the permanence (time spent) of large predatory fish along the ladder, the injuries imposed by piranhas during passage and the presence of other vertebrate predators were investigated. From December 2002 to October 2003, sampling was conducted in four regions (downstream, along the ladder, in the forebay, and upstream of the reservoir) using gillnets, cast nets and counts or visual observations. The captured fish were tagged with thread and beads, and any mutilations were registered. Fish, birds and dolphins were the main predator groups observed, with a predominance of the first two groups. The entrance to the ladder, in the downstream region, was the area with the highest number of large predators and was the only region with relevant non-fish vertebrates. The main predatory fish species were Rhaphiodon vulpinus, Hydrolycus armatus, and Serrasalmus rhombeus. Tagged individuals were detected predating along the ladder for up to 90 days. Mutilations caused by Serrasalmus attacks were noted in 36% of species and 4% of individuals at the top of the ladder. Our results suggested that the high density of fish in the restricted ladder environment, which is associated with injuries suffered along the ladder course and the presence of multiple predator groups with different predation strategies, transformed the fish corridor into a hotspot for predation.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252012000400001&lng=en&tlng=enDamFish migrationFish passPiscivoresSerrasalmus |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Angelo Antonio Agostinho Carlos Sergio Agostinho Fernando Mayer Pelicice Elineide Eugênio Marques |
spellingShingle |
Angelo Antonio Agostinho Carlos Sergio Agostinho Fernando Mayer Pelicice Elineide Eugênio Marques Fish ladders: safe fish passage or hotspot for predation? Neotropical Ichthyology Dam Fish migration Fish pass Piscivores Serrasalmus |
author_facet |
Angelo Antonio Agostinho Carlos Sergio Agostinho Fernando Mayer Pelicice Elineide Eugênio Marques |
author_sort |
Angelo Antonio Agostinho |
title |
Fish ladders: safe fish passage or hotspot for predation? |
title_short |
Fish ladders: safe fish passage or hotspot for predation? |
title_full |
Fish ladders: safe fish passage or hotspot for predation? |
title_fullStr |
Fish ladders: safe fish passage or hotspot for predation? |
title_full_unstemmed |
Fish ladders: safe fish passage or hotspot for predation? |
title_sort |
fish ladders: safe fish passage or hotspot for predation? |
publisher |
Sociedade Brasileira de Ictiologia |
series |
Neotropical Ichthyology |
issn |
1982-0224 |
description |
Fish ladders are a strategy for conserving biodiversity, as they can provide connectivity between fragmented habitats and reduce predation on shoals that accumulate immediately below dams. Although the impact of predation downstream of reservoirs has been investigated, especially in juvenile salmonids during their downstream movements, nothing is known about predation on Neotropical fish in the attraction and containment areas commonly found in translocation facilities. This study analysed predation in a fish passage system at the Lajeado Dam on the Tocantins River in Brazil. The abundance, distribution, and the permanence (time spent) of large predatory fish along the ladder, the injuries imposed by piranhas during passage and the presence of other vertebrate predators were investigated. From December 2002 to October 2003, sampling was conducted in four regions (downstream, along the ladder, in the forebay, and upstream of the reservoir) using gillnets, cast nets and counts or visual observations. The captured fish were tagged with thread and beads, and any mutilations were registered. Fish, birds and dolphins were the main predator groups observed, with a predominance of the first two groups. The entrance to the ladder, in the downstream region, was the area with the highest number of large predators and was the only region with relevant non-fish vertebrates. The main predatory fish species were Rhaphiodon vulpinus, Hydrolycus armatus, and Serrasalmus rhombeus. Tagged individuals were detected predating along the ladder for up to 90 days. Mutilations caused by Serrasalmus attacks were noted in 36% of species and 4% of individuals at the top of the ladder. Our results suggested that the high density of fish in the restricted ladder environment, which is associated with injuries suffered along the ladder course and the presence of multiple predator groups with different predation strategies, transformed the fish corridor into a hotspot for predation. |
topic |
Dam Fish migration Fish pass Piscivores Serrasalmus |
url |
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252012000400001&lng=en&tlng=en |
work_keys_str_mv |
AT angeloantonioagostinho fishladderssafefishpassageorhotspotforpredation AT carlossergioagostinho fishladderssafefishpassageorhotspotforpredation AT fernandomayerpelicice fishladderssafefishpassageorhotspotforpredation AT elineideeugeniomarques fishladderssafefishpassageorhotspotforpredation |
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