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Diversity in migratory patterns among Neotropical fishes in a highly regulated river basin

Authors

  • M. C. Makrakis,

    Corresponding author
    1. Universidade Estadual do Oeste do Paraná, GETECH (Grupo de Pesquisas em Tecnologia de Produção e Conservação de Recursos Pesqueiros e Hídricos), Rua da Faculdade, 645, Jardim Santa Maria, 85903-000 Toledo, Paraná, Brazil
      Tel.: +55 45 3379 7080; email: mmakrakis@terra.com.br
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  • L. E. Miranda,

    1. U.S. Geological Survey, Mississippi Cooperative Fish and Wildlife Research Unit, P. O. Box 9691, Mississippi State, MS 39762, U.S.A.
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  • S. Makrakis,

    1. Universidade Estadual do Oeste do Paraná, GETECH (Grupo de Pesquisas em Tecnologia de Produção e Conservação de Recursos Pesqueiros e Hídricos), Rua da Faculdade, 645, Jardim Santa Maria, 85903-000 Toledo, Paraná, Brazil
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  • H. M. Fontes Júnior,

    1. Itaipu Binacional, Divisão de Reservatórios, Avenida Tancredo Neves, 6731, 85856-970 Foz do Iguaçu, Paraná, Brazil
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  • W. G. Morlis,

    1. Itaipu Binacional, Assumpção, Cale De La Residenta, 1075, CC6919, Paraguay
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  • J. H. P. Dias,

    1. Companhia Energética de São Paulo (CESP), Rodovia Marechal Rondon, km 667, 16920-000 Castilho, São Paulo, Brazil
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  • J. O. Garcia

    1. Entidad Binacional Yacyreta, Villa Permanente, s|n Ituzaingó, Corrientes W3302, Argentina
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Tel.: +55 45 3379 7080; email: mmakrakis@terra.com.br

Abstract

Migratory behaviour of selected fish species is described in the Paraná River, Brazil–Argentina–Paraguay, to search for patterns relevant to tropical regulated river systems. In a 10 year mark–recapture study, spanning a 1425 km section of the river, 32 867 fishes composed of 18 species were released and 1083 fishes were recaptured. The fishes recaptured were at liberty an average 166 days (maximum 1548 days) and travelled an average 35 km (range 0–625 km). Cluster analysis applied to variables descriptive of movement behaviour identified four general movement patterns. Cluster 1 included species that moved long distances (mean 164 km) upstream (54%) and downstream (40%) the mainstem river and showed high incidence (27%) of passage through dams; cluster 2 also exhibited high rate of movement along the mainstem (49% upstream, 13% downstream), but moved small distances (mean 10 km); cluster 3 included the most fishes moving laterally into tributaries (45%) or not moving at all (25%), but little downstream movement (8%); fishes in cluster 4 exhibited little upstream movement (13%) and farthest downstream movements (mean 41 km). Whereas species could be numerically clustered with statistical models, a species ordination showed ample spread, suggesting that species exhibit diverse movement patterns that cannot be easily classified into just a few classes. The cluster and ordination procedures also showed that adults and juveniles of the same species exhibit similar movement patterns. Conventional concepts about Neotropical migratory fishes portray them as travelling long distances upstream. The present results broaden these concepts suggesting that migratory movements are more diverse, could be long, short or at times absent, upriver, downriver or lateral, and the diversity of movements can vary within and among species. The intense lateral migrations exhibited by a diversity of species, especially to and from large tributaries (above reservoirs) and reservoir tributaries, illustrate the importance of these habitats for the fish species life cycle. Considering that the Paraná River is highly impounded, special attention should be given to the few remaining low-impact habitats as they continue to be targets of hydropower development that will probably intensify the effects on migratory fish stocks.

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