Diel variation in the ascent of fishes up an experimental fish ladder at Itaipu Reservoir: fish size, reproductive stage and taxonomic group influences

Abstract

In this study, we evaluated the fish ascent in the experimental ladder at Itaipu Reservoir (Paraná State, Brazil), in relation to diel variation, fish size, reproductive stages and species composition. The study was carried out from October, 1995 to February, 1996 and from November, 1996 to January, 1997 at two points on the ladder (boxes at heights of 10 and 27 m). Twenty-two species were recorded, and Prochilodus lineatus, Pimelodus maculatus, Leporinus obtusidens, Schizodon borellii and Leporinus friderici accounted for 86.6 % of the total catch. Fish length did not differ between diel periods and boxes. On the other hand, fish abundance of the main species was significantly influenced by box position, reproductive stage and diel period. The higher box showed lower abundance, suggesting some selectivity in ascension. The ability to ascend the ladder did not show any relationship with reproductive migration, since non-reproductive adults comprised most of the catch. An interesting finding is that the major taxonomic groups showed specific diel preferences in ascending the ladder: Characiformes ascended the ladder predominantly during daylight, whereas Siluriformes migrated at night. These results emphasize how complex ladders are as management tools, and stress the need to acquire information on several aspects as a condition to achieve conservation goals.Nesse estudo, a transposição de peixes na escada experimental do reservatório de Itaipu (Paraná, Brasil) foi avaliada em relação à variação diária, tamanho dos peixes, estágios reprodutivos e a composição das espécies. O estudo foi conduzido de Outubro de 1995 a Fevereiro de 1996, e de Novembro de 1996 a Janeiro de 1997, em dois trechos da escada (caixas a 10 e 27 m de altura). Vinte e duas espécies foram registradas, e Prochilodus lineatus, Pimelodus maculatus, Leporinus obtusidens, Schizodon borellii e Leporinus friderici compuseram 86,6% das capturas. O tamanho dos peixes não diferiu entre os períodos do dia e caixas. Por outro lado, a abundância das principais espécies foi significativamente influenciada pela posição das caixas, estágio de reprodução e período do dia. A caixa superior tendeu a apresentar menor abundância de peixes, sugerindo certa seletividade na subida. A habilidade em ascender a escada não esteve relacionada com a migração reprodutiva, visto que adultos não-reprodutivos compuseram a maior parte das capturas. Um padrão interessante foi a preferência, apresentada pelos grandes grupos taxonômicos, por períodos específicos do dia na ascensão da escada: os Characiformes subiram a escada predominantemente durante o dia, enquanto os Siluriformes durante a noite. Esses resultados enfatizam o quão complexas são as escadas como ferramentas de manejo, e realçam a necessidade de ampliar o nível de informações sobre diversos aspectos como condição chave para que metas conservacionistas sejam alcançadas.

Fish passages in South America: an overview of studied facilities and research effort

“…Regarding research questions (sensu Roscoe, Hinch, 2010), most studies addressed efficiency questions, i.e., issues related to fish passage, such as abundance and species composition within the fishway (e.g., Bowen et al, 2006;Makrakis et al, 2007a;, or the proportion of fish ascending and descending the facility (e.g., Agostinho et al, 2007d;Fernandez et al, 2007a;Makrakis et al, 2010). A smaller number addressed mechanism questions, which investigated how passage is affected by operation (e.g., Pompeu, Martinez, 2005), environmental variables (e.g., Fernandez et al, 2007b;Pereira-Assis et al, 2009a), and swimming ability (e.g., Santos et al, 2007;Assumpção et al, 2012;.…”

Optimal swim speeds by respirometer: an analysis of three neotropical species

“…Fish of these genera are considered target species in fish passes designs. They have a wide distribution in Brazilian basins and their presence is frequently common downstream dams (Pompeu & Martinez, 2006;Fernandez et al, 2007;Alves, 2007). The knowledge of P. costatus swimming ability is especially important because Prochilodontids constitutes a large proportion of catches, among the characins in Latin America (Marmulla, 2001), and no information on their swimming performance is currently available.…”

Fish passage post-construction issues: analysis of distribution, attraction and passage efficiency metrics at the Baguari Dam fish ladder to approach the problem

“…Significant higher abundance was observed only for the non-migratory group in the lower stretch of the fish ladder which means that the M and MA species were able to move upstream along the facility. Agostinho et al (2007c), Makrakis et al (2007), and Fernandez et al (2007b) observed that significantly fewer fish were sampled in the upper parts of the fish ladder of the Lajeado Dam, Engenheiro Sérgio da Motta Dam and the experimental facility at Itaipu Dam, respectively. The ascension of fish depends of various factors, from diel period to correct hydraulics in the passage that allows fish to negotiate the passage through the pools in a shorter time period.…”

“…However, a secondary objective of keeping fisheries stocks in the reservoir had been considered for fish passages in Brazil (Godinho & Kynard, 2008) and only broader studies to evaluate the efficiency of these facilities would be able to determine which objective is being achieved (Pompeu et al, 2012). Nevertheless, basic data regarding selectivity (Agostinho et al, 2002;Fernandez et al, 2007b), ascent Agostinho et al, 2007c;Makrakis et al, 2011) and influence of abiotic factors in fish movements (Fernandez et al, 2007a;Bizzotto et al, 2009) gathered from studies focused in the fish passage itself is still very important due to their possible use for designing new structures. Pompeu et al (2012) have already stated that improvements were achieved to pass fish upstream based on data gathered with basic monitoring and with the development of new research projects to approach specific variables such swimming capability.…”

“…Those effects vary from changes in the fluvial geomorphology altering erosion, transport and deposition of sediment to species diversity and abundance reduction (Schilt, 2007). Accordingly, dams constitute an obstruction to the movements of migratory fish species (Pelicice & Agostinho, 2007) fragmenting the aquatic environment and blocking the accessibility to critical habitats such as reproductive sites (Fernandez et al, 2007b). Therefore, blockage of migratory pathways and consequent reduction in life-cycle success could eliminate diadromous and potamodromous species from different river basins Okada et al, 2005;Williams et al, 2011).…”