Upstream fish passage was evaluated during 12 months in the vertical-slot Igarapava Fish Ladder constructed around Igarapava Dam, in the heavily dammed Grande River, Southeast Brazil. A video monitoring system was used to observe 61,621 fish that passed the ladder, of which 93.5% were identified to 15 taxa. Among the migratory species, the most abundant were Pimelodus maculatus (33.6% of all fish), Leporinus octofasciatus (31.4%), Leporinus friderici (4.5%), and Prochilodus lineatus (3.1%). Seven taxa were classified as nonmigratory, and of these taxa, the small Bryconamericus stramineus was the most abundant (12.7%) of all fishes. Passage of the 'nonmigratory' taxa upstream in the ladder shows they are migratory in this system and have a strong behavioural drive to move to upstream habitat. Passage of most taxa had a strong seasonal pattern. While some species passed primarily during the day, others showed a distinct nocturnal pattern. Lunar phase and water temperature also strongly affected passage of some taxa. Rainfall and dam discharge had a small or null influence on most taxa; perhaps due to the fairly small catchment area of the reservoir and the highly regulated discharge at Igarapava Dam.

The catfish yellow-mandi, Pimelodus maculatus, is a valuable sporting and commercial fish of inland waters of Southeast Brazil including Igarapava Reservoir. It is a short-distance migrant that needs shorter stretches of free-flowing river to spawn compared to other Neotropical migrants. Igarapava Reservoir is one the 13 hydroelectric reservoirs, arranged in a cascade fashion, impounding the 1,300 km-long Grande River, SE Brazil. In this paper, we examined reproductive features and recruitment of the yellow-mandi in Igarapava Reservoir. We also evaluated the role of the Igarapava Fish Ladder (IFL) built around Igarapava Dam on the sustainability of its fisheries. Female adult yellow-mandis that were gill netted (nets of 8-20 cm stretchmesh) during the reproductive season of 2002/2003, showed adequate ovarian development, indicated by the gonadosomatic index (12.9 ± 2.1, at mature stage) and absolute fecundity (413,794 ± 206,259; range = 125,601-742,026), which were higher than those found in the literature. Postovulatory follicles present in ovarian tissue of 32% of the females examined showed that they possibly could have spawned in the reservoir area. Gill nets of 3-5 cm stretch-mesh aimed at capturing juvenile yellow-mandi were unproductive. These results indicated that Igarapava Reservoir and its reduced catchment area did not provide adequate conditions for recruitment of the yellow-mandi. This fish, the most abundant in the IFL, and those reaching the reservoir tended to remain there since no upstream passage mechanism is present. Thus, the IFL apparently was responsible for maintaining the Igarapava Reservoir stock of yellow-mandi.O mandi-amarelo, Pimelodus maculatus, é um peixe importante nas pescarias comercial e desportiva de águas continentais do Sudeste do Brasil, incluindo o reservatório de Igarapava. Ele é um migrador de curta distância que necessita de segmentos mais curtos de fluxos livres de rios para desovar do que outros migradores. O reservatório de Igarapava é um dos 13 reservatórios hidrelétricos, dispostos em cascata, que fragmentaram os 1.300 km do rio Grande, no sudeste do Brasil. Neste trabalho, examinamos aspectos reprodutivos e o recrutamento do mandi-amarelo no reservatório de Igarapava. Avaliamos também o papel da escada de peixes, construída em torno da barragem de Igarapava, na sustentabilidade da pesca desse peixe no respectivo reservatório. Fêmeas de mandis-amarelos adultas, capturadas durante o período reprodutivo, com redes de emalhar (tamanho de malha entre 8 e 20 cm, medido entre nós opostos), exibiram adequado desenvolvimento ovariano, indicado pelo índice gonadossomático (12,9 ± 2,1, no estádio maduro) e fecundidade absoluta (413.794 ± 206.259; amplitude = 125.601-742.026). Esses valores foram mais altos do que os registrados na literatura. Folículos pós-ovulatórios, presentes no ovário de 32% das fêmeas examinadas indicaram que, possivelmente, elas poderiam ter desovado no reservatório. Redes de emalhar de 3-5 cm de malha (medida entre nós opostos), colocadas com o objeti...