ALBERT

Description:    Millions of fish ascend through fishways in South America every year, but there is no evidence that downstream passage is occurring in large dams. Based on this concern, this study monitored the fish ladder at Lajeado Dam, Tocantins River, a large Amazonian tributary. To investigate the extent of downstream movements through the fishway, ascending and descending movements were quantified between November 2007 and October 2008. Monitoring showed that the ladder is restrictive to many species in both directions, but downstream passage was much more limited: almost all fish captured in the ladder (99.5%) were ascending the facility. Consequently, the numerical ratio between ascending and descending fish (ind./m 2 ) showed high positive values throughout the year (1508:1 on average); migratory species showed higher ratios. All results showed that downstream passage through the ladder is very limited, and that the facility allows only one-way movements (i.e., upstream). This is the first empirical evidence showing that a ladder is critically deficient for downstream passage of fishes in South America. Content Type Journal Article Pages 1-12 DOI 10.1007/s10750-011-0787-0 Authors Carlos Sérgio Agostinho, Núcleo de Estudos Ambientais (Neamb), Universidade Federal do Tocantins, Rua 3, Quadra 17, Jardim dos Ipês, Porto Nacional, TO 77500-000, Brazil Fernando Mayer Pelicice, Núcleo de Estudos Ambientais (Neamb), Universidade Federal do Tocantins, Rua 3, Quadra 17, Jardim dos Ipês, Porto Nacional, TO 77500-000, Brazil Elineide Eugênio Marques, Núcleo de Estudos Ambientais (Neamb), Universidade Federal do Tocantins, Rua 3, Quadra 17, Jardim dos Ipês, Porto Nacional, TO 77500-000, Brazil Anderson Brito Soares, Núcleo de Estudos Ambientais (Neamb), Universidade Federal do Tocantins, Rua 3, Quadra 17, Jardim dos Ipês, Porto Nacional, TO 77500-000, Brazil Deusimar Augusto Alves de Almeida, Investco S.A., Miracema do Tocantins, TO, Brazil Journal Hydrobiologia Online ISSN 1573-5117 Print ISSN 0018-8158